Python/ceval.c

/* Execute compiled code */

/* XXX TO DO:
   XXX speed up searching for keywords by using a dictionary
   XXX document it!
   */

/* enable more aggressive intra-module optimizations, where available */
#define PY_LOCAL_AGGRESSIVE

#include "Python.h"

#include "code.h"
#include "frameobject.h"
#include "eval.h"
#include "opcode.h"
#include "structmember.h"

#include <ctype.h>

#ifndef WITH_TSC

#define READ_TIMESTAMP(var)

#else

typedef unsigned long long uint64;

/* PowerPC support.
   "__ppc__" appears to be the preprocessor definition to detect on OS X, whereas
   "__powerpc__" appears to be the correct one for Linux with GCC
*/
#if defined(__ppc__) || defined (__powerpc__)

#define READ_TIMESTAMP(var) ppc_getcounter(&var)

static void
ppc_getcounter(uint64 *v)
{
    register unsigned long tbu, tb, tbu2;

  loop:
    asm volatile ("mftbu %0" : "=r" (tbu) );
    asm volatile ("mftb  %0" : "=r" (tb)  );
    asm volatile ("mftbu %0" : "=r" (tbu2));
    if (__builtin_expect(tbu != tbu2, 0)) goto loop;

    /* The slightly peculiar way of writing the next lines is
       compiled better by GCC than any other way I tried. */
    ((long*)(v))[0] = tbu;
    ((long*)(v))[1] = tb;
}

#elif defined(__i386__)

/* this is for linux/x86 (and probably any other GCC/x86 combo) */

#define READ_TIMESTAMP(val) \
     __asm__ __volatile__("rdtsc" : "=A" (val))

#elif defined(__x86_64__)

/* for gcc/x86_64, the "A" constraint in DI mode means *either* rax *or* rdx;
   not edx:eax as it does for i386.  Since rdtsc puts its result in edx:eax
   even in 64-bit mode, we need to use "a" and "d" for the lower and upper
   32-bit pieces of the result. */

#define READ_TIMESTAMP(val) do {                        \
    unsigned int h, l;                                  \
    __asm__ __volatile__("rdtsc" : "=a" (l), "=d" (h)); \
    (val) = ((uint64)l) | (((uint64)h) << 32);          \
    } while(0)


#else

#error "Don't know how to implement timestamp counter for this architecture"

#endif

void dump_tsc(int opcode, int ticked, uint64 inst0, uint64 inst1,
              uint64 loop0, uint64 loop1, uint64 intr0, uint64 intr1)
{
    uint64 intr, inst, loop;
    PyThreadState *tstate = PyThreadState_Get();
    if (!tstate->interp->tscdump)
        return;
    intr = intr1 - intr0;
    inst = inst1 - inst0 - intr;
    loop = loop1 - loop0 - intr;
    fprintf(stderr, "opcode=%03d t=%d inst=%06lld loop=%06lld\n",
            opcode, ticked, inst, loop);
}

#endif

/* Turn this on if your compiler chokes on the big switch: */
/* #define CASE_TOO_BIG 1 */

#ifdef Py_DEBUG
/* For debugging the interpreter: */
#define LLTRACE  1      /* Low-level trace feature */
#define CHECKEXC 1      /* Double-check exception checking */
#endif

typedef PyObject *(*callproc)(PyObject *, PyObject *, PyObject *);

/* Forward declarations */
#ifdef WITH_TSC
static PyObject * call_function(PyObject ***, int, uint64*, uint64*);
#else
static PyObject * call_function(PyObject ***, int);
#endif
static PyObject * fast_function(PyObject *, PyObject ***, int, int, int);
static PyObject * do_call(PyObject *, PyObject ***, int, int);
static PyObject * ext_do_call(PyObject *, PyObject ***, int, int, int);
static PyObject * update_keyword_args(PyObject *, int, PyObject ***,
                                      PyObject *);
static PyObject * update_star_args(int, int, PyObject *, PyObject ***);
static PyObject * load_args(PyObject ***, int);
#define CALL_FLAG_VAR 1
#define CALL_FLAG_KW 2

#ifdef LLTRACE
static int lltrace;
static int prtrace(PyObject *, char *);
#endif
static int call_trace(Py_tracefunc, PyObject *, PyFrameObject *,
                      int, PyObject *);
static int call_trace_protected(Py_tracefunc, PyObject *,
                                PyFrameObject *, int, PyObject *);
static void call_exc_trace(Py_tracefunc, PyObject *, PyFrameObject *);
static int maybe_call_line_trace(Py_tracefunc, PyObject *,
                                 PyFrameObject *, int *, int *, int *);

static PyObject * apply_slice(PyObject *, PyObject *, PyObject *);
static int assign_slice(PyObject *, PyObject *,
                        PyObject *, PyObject *);
static PyObject * cmp_outcome(int, PyObject *, PyObject *);
static PyObject * import_from(PyObject *, PyObject *);
static int import_all_from(PyObject *, PyObject *);
static PyObject * build_class(PyObject *, PyObject *, PyObject *);
static int exec_statement(PyFrameObject *,
                          PyObject *, PyObject *, PyObject *);
static void set_exc_info(PyThreadState *, PyObject *, PyObject *, PyObject *);
static void reset_exc_info(PyThreadState *);
static void format_exc_check_arg(PyObject *, char *, PyObject *);
static PyObject * string_concatenate(PyObject *, PyObject *,
                                     PyFrameObject *, unsigned char *);
static PyObject * kwd_as_string(PyObject *);
static PyObject * special_lookup(PyObject *, char *, PyObject **);

#define NAME_ERROR_MSG \
    "name '%.200s' is not defined"
#define GLOBAL_NAME_ERROR_MSG \
    "global name '%.200s' is not defined"
#define UNBOUNDLOCAL_ERROR_MSG \
    "local variable '%.200s' referenced before assignment"
#define UNBOUNDFREE_ERROR_MSG \
    "free variable '%.200s' referenced before assignment" \
    " in enclosing scope"

/* Dynamic execution profile */
#ifdef DYNAMIC_EXECUTION_PROFILE
#ifdef DXPAIRS
static long dxpairs[257][256];
#define dxp dxpairs[256]
#else
static long dxp[256];
#endif
#endif

/* Function call profile */
#ifdef CALL_PROFILE
#define PCALL_NUM 11
static int pcall[PCALL_NUM];

#define PCALL_ALL 0
#define PCALL_FUNCTION 1
#define PCALL_FAST_FUNCTION 2
#define PCALL_FASTER_FUNCTION 3
#define PCALL_METHOD 4
#define PCALL_BOUND_METHOD 5
#define PCALL_CFUNCTION 6
#define PCALL_TYPE 7
#define PCALL_GENERATOR 8
#define PCALL_OTHER 9
#define PCALL_POP 10

/* Notes about the statistics

   PCALL_FAST stats

   FAST_FUNCTION means no argument tuple needs to be created.
   FASTER_FUNCTION means that the fast-path frame setup code is used.

   If there is a method call where the call can be optimized by changing
   the argument tuple and calling the function directly, it gets recorded
   twice.

   As a result, the relationship among the statistics appears to be
   PCALL_ALL == PCALL_FUNCTION + PCALL_METHOD - PCALL_BOUND_METHOD +
                PCALL_CFUNCTION + PCALL_TYPE + PCALL_GENERATOR + PCALL_OTHER
   PCALL_FUNCTION > PCALL_FAST_FUNCTION > PCALL_FASTER_FUNCTION
   PCALL_METHOD > PCALL_BOUND_METHOD
*/

#define PCALL(POS) pcall[POS]++

PyObject *
PyEval_GetCallStats(PyObject *self)
{
    return Py_BuildValue("iiiiiiiiiii",
                         pcall[0], pcall[1], pcall[2], pcall[3],
                         pcall[4], pcall[5], pcall[6], pcall[7],
                         pcall[8], pcall[9], pcall[10]);
}
#else
#define PCALL(O)

PyObject *
PyEval_GetCallStats(PyObject *self)
{
    Py_INCREF(Py_None);
    return Py_None;
}
#endif


#ifdef WITH_THREAD

#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
#include "pythread.h"

static PyThread_type_lock interpreter_lock = 0; /* This is the GIL */
static PyThread_type_lock pending_lock = 0; /* for pending calls */
static long main_thread = 0;

int
PyEval_ThreadsInitialized(void)
{
    return interpreter_lock != 0;
}

void
PyEval_InitThreads(void)
{
    if (interpreter_lock)
        return;
    interpreter_lock = PyThread_allocate_lock();
    PyThread_acquire_lock(interpreter_lock, 1);
    main_thread = PyThread_get_thread_ident();
}

void
PyEval_AcquireLock(void)
{
    PyThread_acquire_lock(interpreter_lock, 1);
}

void
PyEval_ReleaseLock(void)
{
    PyThread_release_lock(interpreter_lock);
}

void
PyEval_AcquireThread(PyThreadState *tstate)
{
    if (tstate == NULL)
        Py_FatalError("PyEval_AcquireThread: NULL new thread state");
    /* Check someone has called PyEval_InitThreads() to create the lock */
    assert(interpreter_lock);
    PyThread_acquire_lock(interpreter_lock, 1);
    if (PyThreadState_Swap(tstate) != NULL)
        Py_FatalError(
            "PyEval_AcquireThread: non-NULL old thread state");
}

void
PyEval_ReleaseThread(PyThreadState *tstate)
{
    if (tstate == NULL)
        Py_FatalError("PyEval_ReleaseThread: NULL thread state");
    if (PyThreadState_Swap(NULL) != tstate)
        Py_FatalError("PyEval_ReleaseThread: wrong thread state");
    PyThread_release_lock(interpreter_lock);
}

/* This function is called from PyOS_AfterFork to ensure that newly
   created child processes don't hold locks referring to threads which
   are not running in the child process.  (This could also be done using
   pthread_atfork mechanism, at least for the pthreads implementation.) */

void
PyEval_ReInitThreads(void)
{
    PyObject *threading, *result;
    PyThreadState *tstate;

    if (!interpreter_lock)
        return;
    /*XXX Can't use PyThread_free_lock here because it does too
      much error-checking.  Doing this cleanly would require
      adding a new function to each thread_*.h.  Instead, just
      create a new lock and waste a little bit of memory */
    interpreter_lock = PyThread_allocate_lock();
    pending_lock = PyThread_allocate_lock();
    PyThread_acquire_lock(interpreter_lock, 1);
    main_thread = PyThread_get_thread_ident();

    /* Update the threading module with the new state.
     */
    tstate = PyThreadState_GET();
    threading = PyMapping_GetItemString(tstate->interp->modules,
                                        "threading");
    if (threading == NULL) {
        /* threading not imported */
        PyErr_Clear();
        return;
    }
    result = PyObject_CallMethod(threading, "_after_fork", NULL);
    if (result == NULL)
        PyErr_WriteUnraisable(threading);
    else
        Py_DECREF(result);
    Py_DECREF(threading);
}
#endif

/* Functions save_thread and restore_thread are always defined so
   dynamically loaded modules needn't be compiled separately for use
   with and without threads: */

PyThreadState *
PyEval_SaveThread(void)
{
    PyThreadState *tstate = PyThreadState_Swap(NULL);
    if (tstate == NULL)
        Py_FatalError("PyEval_SaveThread: NULL tstate");
#ifdef WITH_THREAD
    if (interpreter_lock)
        PyThread_release_lock(interpreter_lock);
#endif
    return tstate;
}

void
PyEval_RestoreThread(PyThreadState *tstate)
{
    if (tstate == NULL)
        Py_FatalError("PyEval_RestoreThread: NULL tstate");
#ifdef WITH_THREAD
    if (interpreter_lock) {
        int err = errno;
        PyThread_acquire_lock(interpreter_lock, 1);
        errno = err;
    }
#endif
    PyThreadState_Swap(tstate);
}


/* Mechanism whereby asynchronously executing callbacks (e.g. UNIX
   signal handlers or Mac I/O completion routines) can schedule calls
   to a function to be called synchronously.
   The synchronous function is called with one void* argument.
   It should return 0 for success or -1 for failure -- failure should
   be accompanied by an exception.

   If registry succeeds, the registry function returns 0; if it fails
   (e.g. due to too many pending calls) it returns -1 (without setting
   an exception condition).

   Note that because registry may occur from within signal handlers,
   or other asynchronous events, calling malloc() is unsafe!

#ifdef WITH_THREAD
   Any thread can schedule pending calls, but only the main thread
   will execute them.
   There is no facility to schedule calls to a particular thread, but
   that should be easy to change, should that ever be required.  In
   that case, the static variables here should go into the python
   threadstate.
#endif
*/

#ifdef WITH_THREAD

/* The WITH_THREAD implementation is thread-safe.  It allows
   scheduling to be made from any thread, and even from an executing
   callback.
 */

#define NPENDINGCALLS 32
static struct {
    int (*func)(void *);
    void *arg;
} pendingcalls[NPENDINGCALLS];
static int pendingfirst = 0;
static int pendinglast = 0;
static volatile int pendingcalls_to_do = 1; /* trigger initialization of lock */
static char pendingbusy = 0;

int
Py_AddPendingCall(int (*func)(void *), void *arg)
{
    int i, j, result=0;
    PyThread_type_lock lock = pending_lock;

    /* try a few times for the lock.  Since this mechanism is used
     * for signal handling (on the main thread), there is a (slim)
     * chance that a signal is delivered on the same thread while we
     * hold the lock during the Py_MakePendingCalls() function.
     * This avoids a deadlock in that case.
     * Note that signals can be delivered on any thread.  In particular,
     * on Windows, a SIGINT is delivered on a system-created worker
     * thread.
     * We also check for lock being NULL, in the unlikely case that
     * this function is called before any bytecode evaluation takes place.
     */
    if (lock != NULL) {
        for (i = 0; i<100; i++) {
            if (PyThread_acquire_lock(lock, NOWAIT_LOCK))
                break;
        }
        if (i == 100)
            return -1;
    }

    i = pendinglast;
    j = (i + 1) % NPENDINGCALLS;
    if (j == pendingfirst) {
        result = -1; /* Queue full */
    } else {
        pendingcalls[i].func = func;
        pendingcalls[i].arg = arg;
        pendinglast = j;
    }
    /* signal main loop */
    _Py_Ticker = 0;
    pendingcalls_to_do = 1;
    if (lock != NULL)
        PyThread_release_lock(lock);
    return result;
}

int
Py_MakePendingCalls(void)
{
    int i;
    int r = 0;

    if (!pending_lock) {
        /* initial allocation of the lock */
        pending_lock = PyThread_allocate_lock();
        if (pending_lock == NULL)
            return -1;
    }

    /* only service pending calls on main thread */
    if (main_thread && PyThread_get_thread_ident() != main_thread)
        return 0;
    /* don't perform recursive pending calls */
    if (pendingbusy)
        return 0;
    pendingbusy = 1;
    /* perform a bounded number of calls, in case of recursion */
    for (i=0; i<NPENDINGCALLS; i++) {
        int j;
        int (*func)(void *);
        void *arg = NULL;

        /* pop one item off the queue while holding the lock */
        PyThread_acquire_lock(pending_lock, WAIT_LOCK);
        j = pendingfirst;
        if (j == pendinglast) {
            func = NULL; /* Queue empty */
        } else {
            func = pendingcalls[j].func;
            arg = pendingcalls[j].arg;
            pendingfirst = (j + 1) % NPENDINGCALLS;
        }
        pendingcalls_to_do = pendingfirst != pendinglast;
        PyThread_release_lock(pending_lock);
        /* having released the lock, perform the callback */
        if (func == NULL)
            break;
        r = func(arg);
        if (r)
            break;
    }
    pendingbusy = 0;
    return r;
}

#else /* if ! defined WITH_THREAD */

/*
   WARNING!  ASYNCHRONOUSLY EXECUTING CODE!
   This code is used for signal handling in python that isn't built
   with WITH_THREAD.
   Don't use this implementation when Py_AddPendingCalls() can happen
   on a different thread!

   There are two possible race conditions:
   (1) nested asynchronous calls to Py_AddPendingCall()
   (2) AddPendingCall() calls made while pending calls are being processed.

   (1) is very unlikely because typically signal delivery
   is blocked during signal handling.  So it should be impossible.
   (2) is a real possibility.
   The current code is safe against (2), but not against (1).
   The safety against (2) is derived from the fact that only one
   thread is present, interrupted by signals, and that the critical
   section is protected with the "busy" variable.  On Windows, which
   delivers SIGINT on a system thread, this does not hold and therefore
   Windows really shouldn't use this version.
   The two threads could theoretically wiggle around the "busy" variable.
*/

#define NPENDINGCALLS 32
static struct {
    int (*func)(void *);
    void *arg;
} pendingcalls[NPENDINGCALLS];
static volatile int pendingfirst = 0;
static volatile int pendinglast = 0;
static volatile int pendingcalls_to_do = 0;

int
Py_AddPendingCall(int (*func)(void *), void *arg)
{
    static volatile int busy = 0;
    int i, j;
    /* XXX Begin critical section */
    if (busy)
        return -1;
    busy = 1;
    i = pendinglast;
    j = (i + 1) % NPENDINGCALLS;
    if (j == pendingfirst) {
        busy = 0;
        return -1; /* Queue full */
    }
    pendingcalls[i].func = func;
    pendingcalls[i].arg = arg;
    pendinglast = j;

    _Py_Ticker = 0;
    pendingcalls_to_do = 1; /* Signal main loop */
    busy = 0;
    /* XXX End critical section */
    return 0;
}

int
Py_MakePendingCalls(void)
{
    static int busy = 0;
    if (busy)
        return 0;
    busy = 1;
    pendingcalls_to_do = 0;
    for (;;) {
        int i;
        int (*func)(void *);
        void *arg;
        i = pendingfirst;
        if (i == pendinglast)
            break; /* Queue empty */
        func = pendingcalls[i].func;
        arg = pendingcalls[i].arg;
        pendingfirst = (i + 1) % NPENDINGCALLS;
        if (func(arg) < 0) {
            busy = 0;
            pendingcalls_to_do = 1; /* We're not done yet */
            return -1;
        }
    }
    busy = 0;
    return 0;
}

#endif /* WITH_THREAD */


/* The interpreter's recursion limit */

#ifndef Py_DEFAULT_RECURSION_LIMIT
#define Py_DEFAULT_RECURSION_LIMIT 1000
#endif
static int recursion_limit = Py_DEFAULT_RECURSION_LIMIT;
int _Py_CheckRecursionLimit = Py_DEFAULT_RECURSION_LIMIT;

int
Py_GetRecursionLimit(void)
{
    return recursion_limit;
}

void
Py_SetRecursionLimit(int new_limit)
{
    recursion_limit = new_limit;
    _Py_CheckRecursionLimit = recursion_limit;
}

/* the macro Py_EnterRecursiveCall() only calls _Py_CheckRecursiveCall()
   if the recursion_depth reaches _Py_CheckRecursionLimit.
   If USE_STACKCHECK, the macro decrements _Py_CheckRecursionLimit
   to guarantee that _Py_CheckRecursiveCall() is regularly called.
   Without USE_STACKCHECK, there is no need for this. */
int
_Py_CheckRecursiveCall(char *where)
{
    PyThreadState *tstate = PyThreadState_GET();

#ifdef USE_STACKCHECK
    if (PyOS_CheckStack()) {
        --tstate->recursion_depth;
        PyErr_SetString(PyExc_MemoryError, "Stack overflow");
        return -1;
    }
#endif
    if (tstate->recursion_depth > recursion_limit) {
        --tstate->recursion_depth;
        PyErr_Format(PyExc_RuntimeError,
                     "maximum recursion depth exceeded%s",
                     where);
        return -1;
    }
    _Py_CheckRecursionLimit = recursion_limit;
    return 0;
}

/* Status code for main loop (reason for stack unwind) */
enum why_code {
        WHY_NOT =       0x0001, /* No error */
        WHY_EXCEPTION = 0x0002, /* Exception occurred */
        WHY_RERAISE =   0x0004, /* Exception re-raised by 'finally' */
        WHY_RETURN =    0x0008, /* 'return' statement */
        WHY_BREAK =     0x0010, /* 'break' statement */
        WHY_CONTINUE =  0x0020, /* 'continue' statement */
        WHY_YIELD =     0x0040  /* 'yield' operator */
};

static enum why_code do_raise(PyObject *, PyObject *, PyObject *);
static int unpack_iterable(PyObject *, int, PyObject **);

/* Records whether tracing is on for any thread.  Counts the number of
   threads for which tstate->c_tracefunc is non-NULL, so if the value
   is 0, we know we don't have to check this thread's c_tracefunc.
   This speeds up the if statement in PyEval_EvalFrameEx() after
   fast_next_opcode*/
static int _Py_TracingPossible = 0;

/* for manipulating the thread switch and periodic "stuff" - used to be
   per thread, now just a pair o' globals */
int _Py_CheckInterval = 100;
volatile int _Py_Ticker = 0; /* so that we hit a "tick" first thing */

PyObject *
PyEval_EvalCode(PyCodeObject *co, PyObject *globals, PyObject *locals)
{
    return PyEval_EvalCodeEx(co,
                      globals, locals,
                      (PyObject **)NULL, 0,
                      (PyObject **)NULL, 0,
                      (PyObject **)NULL, 0,
                      NULL);
}


/* Interpreter main loop */

PyObject *
PyEval_EvalFrame(PyFrameObject *f) {
    /* This is for backward compatibility with extension modules that
       used this API; core interpreter code should call
       PyEval_EvalFrameEx() */
    return PyEval_EvalFrameEx(f, 0);
}

PyObject *
PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
{
#ifdef DXPAIRS
    int lastopcode = 0;
#endif
    register PyObject **stack_pointer;  /* Next free slot in value stack */
    register unsigned char *next_instr;
    register int opcode;        /* Current opcode */
    register int oparg;         /* Current opcode argument, if any */
    register enum why_code why; /* Reason for block stack unwind */
    register int err;           /* Error status -- nonzero if error */
    register PyObject *x;       /* Result object -- NULL if error */
    register PyObject *v;       /* Temporary objects popped off stack */
    register PyObject *w;
    register PyObject *u;
    register PyObject *t;
    register PyObject *stream = NULL;    /* for PRINT opcodes */
    register PyObject **fastlocals, **freevars;
    PyObject *retval = NULL;            /* Return value */
    PyThreadState *tstate = PyThreadState_GET();
    PyCodeObject *co;

    /* when tracing we set things up so that

           not (instr_lb <= current_bytecode_offset < instr_ub)

       is true when the line being executed has changed.  The
       initial values are such as to make this false the first
       time it is tested. */
    int instr_ub = -1, instr_lb = 0, instr_prev = -1;

    unsigned char *first_instr;
    PyObject *names;
    PyObject *consts;
#if defined(Py_DEBUG) || defined(LLTRACE)
    /* Make it easier to find out where we are with a debugger */
    char *filename;
#endif

/* Tuple access macros */

#ifndef Py_DEBUG
#define GETITEM(v, i) PyTuple_GET_ITEM((PyTupleObject *)(v), (i))
#else
#define GETITEM(v, i) PyTuple_GetItem((v), (i))
#endif

#ifdef WITH_TSC
/* Use Pentium timestamp counter to mark certain events:
   inst0 -- beginning of switch statement for opcode dispatch
   inst1 -- end of switch statement (may be skipped)
   loop0 -- the top of the mainloop
   loop1 -- place where control returns again to top of mainloop
            (may be skipped)
   intr1 -- beginning of long interruption
   intr2 -- end of long interruption

   Many opcodes call out to helper C functions.  In some cases, the
   time in those functions should be counted towards the time for the
   opcode, but not in all cases.  For example, a CALL_FUNCTION opcode
   calls another Python function; there's no point in charge all the
   bytecode executed by the called function to the caller.

   It's hard to make a useful judgement statically.  In the presence
   of operator overloading, it's impossible to tell if a call will
   execute new Python code or not.

   It's a case-by-case judgement.  I'll use intr1 for the following
   cases:

   EXEC_STMT
   IMPORT_STAR
   IMPORT_FROM
   CALL_FUNCTION (and friends)

 */
    uint64 inst0, inst1, loop0, loop1, intr0 = 0, intr1 = 0;
    int ticked = 0;

    READ_TIMESTAMP(inst0);
    READ_TIMESTAMP(inst1);
    READ_TIMESTAMP(loop0);
    READ_TIMESTAMP(loop1);

    /* shut up the compiler */
    opcode = 0;
#endif

/* Code access macros */

#define INSTR_OFFSET()  ((int)(next_instr - first_instr))
#define NEXTOP()        (*next_instr++)
#define NEXTARG()       (next_instr += 2, (next_instr[-1]<<8) + next_instr[-2])
#define PEEKARG()       ((next_instr[2]<<8) + next_instr[1])
#define JUMPTO(x)       (next_instr = first_instr + (x))
#define JUMPBY(x)       (next_instr += (x))

/* OpCode prediction macros
    Some opcodes tend to come in pairs thus making it possible to
    predict the second code when the first is run.  For example,
    GET_ITER is often followed by FOR_ITER. And FOR_ITER is often
    followed by STORE_FAST or UNPACK_SEQUENCE.

    Verifying the prediction costs a single high-speed test of a register
    variable against a constant.  If the pairing was good, then the
    processor's own internal branch predication has a high likelihood of
    success, resulting in a nearly zero-overhead transition to the
    next opcode.  A successful prediction saves a trip through the eval-loop
    including its two unpredictable branches, the HAS_ARG test and the
    switch-case.  Combined with the processor's internal branch prediction,
    a successful PREDICT has the effect of making the two opcodes run as if
    they were a single new opcode with the bodies combined.

    If collecting opcode statistics, your choices are to either keep the
    predictions turned-on and interpret the results as if some opcodes
    had been combined or turn-off predictions so that the opcode frequency
    counter updates for both opcodes.
*/

#ifdef DYNAMIC_EXECUTION_PROFILE
#define PREDICT(op)             if (0) goto PRED_##op
#else
#define PREDICT(op)             if (*next_instr == op) goto PRED_##op
#endif

#define PREDICTED(op)           PRED_##op: next_instr++
#define PREDICTED_WITH_ARG(op)  PRED_##op: oparg = PEEKARG(); next_instr += 3

/* Stack manipulation macros */

/* The stack can grow at most MAXINT deep, as co_nlocals and
   co_stacksize are ints. */
#define STACK_LEVEL()     ((int)(stack_pointer - f->f_valuestack))
#define EMPTY()           (STACK_LEVEL() == 0)
#define TOP()             (stack_pointer[-1])
#define SECOND()          (stack_pointer[-2])
#define THIRD()           (stack_pointer[-3])
#define FOURTH()          (stack_pointer[-4])
#define PEEK(n)           (stack_pointer[-(n)])
#define SET_TOP(v)        (stack_pointer[-1] = (v))
#define SET_SECOND(v)     (stack_pointer[-2] = (v))
#define SET_THIRD(v)      (stack_pointer[-3] = (v))
#define SET_FOURTH(v)     (stack_pointer[-4] = (v))
#define SET_VALUE(n, v)   (stack_pointer[-(n)] = (v))
#define BASIC_STACKADJ(n) (stack_pointer += n)
#define BASIC_PUSH(v)     (*stack_pointer++ = (v))
#define BASIC_POP()       (*--stack_pointer)

#ifdef LLTRACE
#define PUSH(v)         { (void)(BASIC_PUSH(v), \
                          lltrace && prtrace(TOP(), "push")); \
                          assert(STACK_LEVEL() <= co->co_stacksize); }
#define POP()           ((void)(lltrace && prtrace(TOP(), "pop")), \
                         BASIC_POP())
#define STACKADJ(n)     { (void)(BASIC_STACKADJ(n), \
                          lltrace && prtrace(TOP(), "stackadj")); \
                          assert(STACK_LEVEL() <= co->co_stacksize); }
#define EXT_POP(STACK_POINTER) ((void)(lltrace && \
                                prtrace((STACK_POINTER)[-1], "ext_pop")), \
                                *--(STACK_POINTER))
#else
#define PUSH(v)                BASIC_PUSH(v)
#define POP()                  BASIC_POP()
#define STACKADJ(n)            BASIC_STACKADJ(n)
#define EXT_POP(STACK_POINTER) (*--(STACK_POINTER))
#endif

/* Local variable macros */

#define GETLOCAL(i)     (fastlocals[i])

/* The SETLOCAL() macro must not DECREF the local variable in-place and
   then store the new value; it must copy the old value to a temporary
   value, then store the new value, and then DECREF the temporary value.
   This is because it is possible that during the DECREF the frame is
   accessed by other code (e.g. a __del__ method or gc.collect()) and the
   variable would be pointing to already-freed memory. */
#define SETLOCAL(i, value)      do { PyObject *tmp = GETLOCAL(i); \
                                     GETLOCAL(i) = value; \
                                     Py_XDECREF(tmp); } while (0)

/* Start of code */

    if (f == NULL)
        return NULL;

    /* push frame */
    if (Py_EnterRecursiveCall(""))
        return NULL;

    tstate->frame = f;

    if (tstate->use_tracing) {
        if (tstate->c_tracefunc != NULL) {
            /* tstate->c_tracefunc, if defined, is a
               function that will be called on *every* entry
               to a code block.  Its return value, if not
               None, is a function that will be called at
               the start of each executed line of code.
               (Actually, the function must return itself
               in order to continue tracing.)  The trace
               functions are called with three arguments:
               a pointer to the current frame, a string
               indicating why the function is called, and
               an argument which depends on the situation.
               The global trace function is also called
               whenever an exception is detected. */
            if (call_trace_protected(tstate->c_tracefunc,
                                     tstate->c_traceobj,
                                     f, PyTrace_CALL, Py_None)) {
                /* Trace function raised an error */
                goto exit_eval_frame;
            }
        }
        if (tstate->c_profilefunc != NULL) {
            /* Similar for c_profilefunc, except it needn't
               return itself and isn't called for "line" events */
            if (call_trace_protected(tstate->c_profilefunc,
                                     tstate->c_profileobj,
                                     f, PyTrace_CALL, Py_None)) {
                /* Profile function raised an error */
                goto exit_eval_frame;
            }
        }
    }

    co = f->f_code;
    names = co->co_names;
    consts = co->co_consts;
    fastlocals = f->f_localsplus;
    freevars = f->f_localsplus + co->co_nlocals;
    first_instr = (unsigned char*) PyString_AS_STRING(co->co_code);
    /* An explanation is in order for the next line.

       f->f_lasti now refers to the index of the last instruction
       executed.  You might think this was obvious from the name, but
       this wasn't always true before 2.3!  PyFrame_New now sets
       f->f_lasti to -1 (i.e. the index *before* the first instruction)
       and YIELD_VALUE doesn't fiddle with f_lasti any more.  So this
       does work.  Promise.

       When the PREDICT() macros are enabled, some opcode pairs follow in
       direct succession without updating f->f_lasti.  A successful
       prediction effectively links the two codes together as if they
       were a single new opcode; accordingly,f->f_lasti will point to
       the first code in the pair (for instance, GET_ITER followed by
       FOR_ITER is effectively a single opcode and f->f_lasti will point
       at to the beginning of the combined pair.)
    */
    next_instr = first_instr + f->f_lasti + 1;
    stack_pointer = f->f_stacktop;
    assert(stack_pointer != NULL);
    f->f_stacktop = NULL;       /* remains NULL unless yield suspends frame */

#ifdef LLTRACE
    lltrace = PyDict_GetItemString(f->f_globals, "__lltrace__") != NULL;
#endif
#if defined(Py_DEBUG) || defined(LLTRACE)
    filename = PyString_AsString(co->co_filename);
#endif

    why = WHY_NOT;
    err = 0;
    x = Py_None;        /* Not a reference, just anything non-NULL */
    w = NULL;

    if (throwflag) { /* support for generator.throw() */
        why = WHY_EXCEPTION;
        goto on_error;
    }

    for (;;) {
#ifdef WITH_TSC
        if (inst1 == 0) {
            /* Almost surely, the opcode executed a break
               or a continue, preventing inst1 from being set
               on the way out of the loop.
            */
            READ_TIMESTAMP(inst1);
            loop1 = inst1;
        }
        dump_tsc(opcode, ticked, inst0, inst1, loop0, loop1,
                 intr0, intr1);
        ticked = 0;
        inst1 = 0;
        intr0 = 0;
        intr1 = 0;
        READ_TIMESTAMP(loop0);
#endif
        assert(stack_pointer >= f->f_valuestack); /* else underflow */
        assert(STACK_LEVEL() <= co->co_stacksize);  /* else overflow */

        /* Do periodic things.  Doing this every time through
           the loop would add too much overhead, so we do it
           only every Nth instruction.  We also do it if
           ``pendingcalls_to_do'' is set, i.e. when an asynchronous
           event needs attention (e.g. a signal handler or
           async I/O handler); see Py_AddPendingCall() and
           Py_MakePendingCalls() above. */

        if (--_Py_Ticker < 0) {
            if (*next_instr == SETUP_FINALLY) {
                /* Make the last opcode before
                   a try: finally: block uninterruptible. */
                goto fast_next_opcode;
            }
            _Py_Ticker = _Py_CheckInterval;
            tstate->tick_counter++;
#ifdef WITH_TSC
            ticked = 1;
#endif
            if (pendingcalls_to_do) {
                if (Py_MakePendingCalls() < 0) {
                    why = WHY_EXCEPTION;
                    goto on_error;
                }
                if (pendingcalls_to_do)
                    /* MakePendingCalls() didn't succeed.
                       Force early re-execution of this
                       "periodic" code, possibly after
                       a thread switch */
                    _Py_Ticker = 0;
            }
#ifdef WITH_THREAD
            if (interpreter_lock) {
                /* Give another thread a chance */

                if (PyThreadState_Swap(NULL) != tstate)
                    Py_FatalError("ceval: tstate mix-up");
                PyThread_release_lock(interpreter_lock);

                /* Other threads may run now */

                PyThread_acquire_lock(interpreter_lock, 1);

                if (PyThreadState_Swap(tstate) != NULL)
                    Py_FatalError("ceval: orphan tstate");

                /* Check for thread interrupts */

                if (tstate->async_exc != NULL) {
                    x = tstate->async_exc;
                    tstate->async_exc = NULL;
                    PyErr_SetNone(x);
                    Py_DECREF(x);
                    why = WHY_EXCEPTION;
                    goto on_error;
                }
            }
#endif
        }

    fast_next_opcode:
        f->f_lasti = INSTR_OFFSET();

        /* line-by-line tracing support */

        if (_Py_TracingPossible &&
            tstate->c_tracefunc != NULL && !tstate->tracing) {
            /* see maybe_call_line_trace
               for expository comments */
            f->f_stacktop = stack_pointer;

            err = maybe_call_line_trace(tstate->c_tracefunc,
                                        tstate->c_traceobj,
                                        f, &instr_lb, &instr_ub,
                                        &instr_prev);
            /* Reload possibly changed frame fields */
            JUMPTO(f->f_lasti);
            if (f->f_stacktop != NULL) {
                stack_pointer = f->f_stacktop;
                f->f_stacktop = NULL;
            }
            if (err) {
                /* trace function raised an exception */
                goto on_error;
            }
        }

        /* Extract opcode and argument */

        opcode = NEXTOP();
        oparg = 0;   /* allows oparg to be stored in a register because
            it doesn't have to be remembered across a full loop */
        if (HAS_ARG(opcode))
            oparg = NEXTARG();
    dispatch_opcode:
#ifdef DYNAMIC_EXECUTION_PROFILE
#ifdef DXPAIRS
        dxpairs[lastopcode][opcode]++;
        lastopcode = opcode;
#endif
        dxp[opcode]++;
#endif

#ifdef LLTRACE
        /* Instruction tracing */

        if (lltrace) {
            if (HAS_ARG(opcode)) {
                printf("%d: %d, %d\n",
                       f->f_lasti, opcode, oparg);
            }
            else {
                printf("%d: %d\n",
                       f->f_lasti, opcode);
            }
        }
#endif

        /* Main switch on opcode */
        READ_TIMESTAMP(inst0);

        switch (opcode) {

        /* BEWARE!
           It is essential that any operation that fails sets either
           x to NULL, err to nonzero, or why to anything but WHY_NOT,
           and that no operation that succeeds does this! */

        /* case STOP_CODE: this is an error! */

        case NOP:
            goto fast_next_opcode;

        case LOAD_FAST:
            x = GETLOCAL(oparg);
            if (x != NULL) {
                Py_INCREF(x);
                PUSH(x);
                goto fast_next_opcode;
            }
            format_exc_check_arg(PyExc_UnboundLocalError,
                UNBOUNDLOCAL_ERROR_MSG,
                PyTuple_GetItem(co->co_varnames, oparg));
            break;

        case LOAD_CONST:
            x = GETITEM(consts, oparg);
            Py_INCREF(x);
            PUSH(x);
            goto fast_next_opcode;

        PREDICTED_WITH_ARG(STORE_FAST);
        case STORE_FAST:
            v = POP();
            SETLOCAL(oparg, v);
            goto fast_next_opcode;

        case POP_TOP:
            v = POP();
            Py_DECREF(v);
            goto fast_next_opcode;

        case ROT_TWO:
            v = TOP();
            w = SECOND();
            SET_TOP(w);
            SET_SECOND(v);
            goto fast_next_opcode;

        case ROT_THREE:
            v = TOP();
            w = SECOND();
            x = THIRD();
            SET_TOP(w);
            SET_SECOND(x);
            SET_THIRD(v);
            goto fast_next_opcode;

        case ROT_FOUR:
            u = TOP();
            v = SECOND();
            w = THIRD();
            x = FOURTH();
            SET_TOP(v);
            SET_SECOND(w);
            SET_THIRD(x);
            SET_FOURTH(u);
            goto fast_next_opcode;

        case DUP_TOP:
            v = TOP();
            Py_INCREF(v);
            PUSH(v);
            goto fast_next_opcode;

        case DUP_TOPX:
            if (oparg == 2) {
                x = TOP();
                Py_INCREF(x);
                w = SECOND();
                Py_INCREF(w);
                STACKADJ(2);
                SET_TOP(x);
                SET_SECOND(w);
                goto fast_next_opcode;
            } else if (oparg == 3) {
                x = TOP();
                Py_INCREF(x);
                w = SECOND();
                Py_INCREF(w);
                v = THIRD();
                Py_INCREF(v);
                STACKADJ(3);
                SET_TOP(x);
                SET_SECOND(w);
                SET_THIRD(v);
                goto fast_next_opcode;
            }
            Py_FatalError("invalid argument to DUP_TOPX"
                          " (bytecode corruption?)");
            /* Never returns, so don't bother to set why. */
            break;

        case UNARY_POSITIVE:
            v = TOP();
            x = PyNumber_Positive(v);
            Py_DECREF(v);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case UNARY_NEGATIVE:
            v = TOP();
            x = PyNumber_Negative(v);
            Py_DECREF(v);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case UNARY_NOT:
            v = TOP();
            err = PyObject_IsTrue(v);
            Py_DECREF(v);
            if (err == 0) {
                Py_INCREF(Py_True);
                SET_TOP(Py_True);
                continue;
            }
            else if (err > 0) {
                Py_INCREF(Py_False);
                SET_TOP(Py_False);
                err = 0;
                continue;
            }
            STACKADJ(-1);
            break;

        case UNARY_CONVERT:
            v = TOP();
            x = PyObject_Repr(v);
            Py_DECREF(v);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case UNARY_INVERT:
            v = TOP();
            x = PyNumber_Invert(v);
            Py_DECREF(v);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case BINARY_POWER:
            w = POP();
            v = TOP();
            x = PyNumber_Power(v, w, Py_None);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case BINARY_MULTIPLY:
            w = POP();
            v = TOP();
            x = PyNumber_Multiply(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case BINARY_DIVIDE:
            if (!_Py_QnewFlag) {
                w = POP();
                v = TOP();
                x = PyNumber_Divide(v, w);
                Py_DECREF(v);
                Py_DECREF(w);
                SET_TOP(x);
                if (x != NULL) continue;
                break;
            }
            /* -Qnew is in effect:  fall through to
               BINARY_TRUE_DIVIDE */
        case BINARY_TRUE_DIVIDE:
            w = POP();
            v = TOP();
            x = PyNumber_TrueDivide(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case BINARY_FLOOR_DIVIDE:
            w = POP();
            v = TOP();
            x = PyNumber_FloorDivide(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case BINARY_MODULO:
            w = POP();
            v = TOP();
            if (PyString_CheckExact(v))
                x = PyString_Format(v, w);
            else
                x = PyNumber_Remainder(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case BINARY_ADD:
            w = POP();
            v = TOP();
            if (PyInt_CheckExact(v) && PyInt_CheckExact(w)) {
                /* INLINE: int + int */
                register long a, b, i;
                a = PyInt_AS_LONG(v);
                b = PyInt_AS_LONG(w);
                /* cast to avoid undefined behaviour
                   on overflow */
                i = (long)((unsigned long)a + b);
                if ((i^a) < 0 && (i^b) < 0)
                    goto slow_add;
                x = PyInt_FromLong(i);
            }
            else if (PyString_CheckExact(v) &&
                     PyString_CheckExact(w)) {
                x = string_concatenate(v, w, f, next_instr);
                /* string_concatenate consumed the ref to v */
                goto skip_decref_vx;
            }
            else {
              slow_add:
                x = PyNumber_Add(v, w);
            }
            Py_DECREF(v);
          skip_decref_vx:
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case BINARY_SUBTRACT:
            w = POP();
            v = TOP();
            if (PyInt_CheckExact(v) && PyInt_CheckExact(w)) {
                /* INLINE: int - int */
                register long a, b, i;
                a = PyInt_AS_LONG(v);
                b = PyInt_AS_LONG(w);
                /* cast to avoid undefined behaviour
                   on overflow */
                i = (long)((unsigned long)a - b);
                if ((i^a) < 0 && (i^~b) < 0)
                    goto slow_sub;
                x = PyInt_FromLong(i);
            }
            else {
              slow_sub:
                x = PyNumber_Subtract(v, w);
            }
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case BINARY_SUBSCR:
            w = POP();
            v = TOP();
            if (PyList_CheckExact(v) && PyInt_CheckExact(w)) {
                /* INLINE: list[int] */
                Py_ssize_t i = PyInt_AsSsize_t(w);
                if (i < 0)
                    i += PyList_GET_SIZE(v);
                if (i >= 0 && i < PyList_GET_SIZE(v)) {
                    x = PyList_GET_ITEM(v, i);
                    Py_INCREF(x);
                }
                else
                    goto slow_get;
            }
            else
              slow_get:
                x = PyObject_GetItem(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case BINARY_LSHIFT:
            w = POP();
            v = TOP();
            x = PyNumber_Lshift(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case BINARY_RSHIFT:
            w = POP();
            v = TOP();
            x = PyNumber_Rshift(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case BINARY_AND:
            w = POP();
            v = TOP();
            x = PyNumber_And(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case BINARY_XOR:
            w = POP();
            v = TOP();
            x = PyNumber_Xor(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case BINARY_OR:
            w = POP();
            v = TOP();
            x = PyNumber_Or(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case LIST_APPEND:
            w = POP();
            v = PEEK(oparg);
            err = PyList_Append(v, w);
            Py_DECREF(w);
            if (err == 0) {
                PREDICT(JUMP_ABSOLUTE);
                continue;
            }
            break;

        case SET_ADD:
            w = POP();
            v = stack_pointer[-oparg];
            err = PySet_Add(v, w);
            Py_DECREF(w);
            if (err == 0) {
                PREDICT(JUMP_ABSOLUTE);
                continue;
            }
            break;

        case INPLACE_POWER:
            w = POP();
            v = TOP();
            x = PyNumber_InPlacePower(v, w, Py_None);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case INPLACE_MULTIPLY:
            w = POP();
            v = TOP();
            x = PyNumber_InPlaceMultiply(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case INPLACE_DIVIDE:
            if (!_Py_QnewFlag) {
                w = POP();
                v = TOP();
                x = PyNumber_InPlaceDivide(v, w);
                Py_DECREF(v);
                Py_DECREF(w);
                SET_TOP(x);
                if (x != NULL) continue;
                break;
            }
            /* -Qnew is in effect:  fall through to
               INPLACE_TRUE_DIVIDE */
        case INPLACE_TRUE_DIVIDE:
            w = POP();
            v = TOP();
            x = PyNumber_InPlaceTrueDivide(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case INPLACE_FLOOR_DIVIDE:
            w = POP();
            v = TOP();
            x = PyNumber_InPlaceFloorDivide(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case INPLACE_MODULO:
            w = POP();
            v = TOP();
            x = PyNumber_InPlaceRemainder(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case INPLACE_ADD:
            w = POP();
            v = TOP();
            if (PyInt_CheckExact(v) && PyInt_CheckExact(w)) {
                /* INLINE: int + int */
                register long a, b, i;
                a = PyInt_AS_LONG(v);
                b = PyInt_AS_LONG(w);
                i = a + b;
                if ((i^a) < 0 && (i^b) < 0)
                    goto slow_iadd;
                x = PyInt_FromLong(i);
            }
            else if (PyString_CheckExact(v) &&
                     PyString_CheckExact(w)) {
                x = string_concatenate(v, w, f, next_instr);
                /* string_concatenate consumed the ref to v */
                goto skip_decref_v;
            }
            else {
              slow_iadd:
                x = PyNumber_InPlaceAdd(v, w);
            }
            Py_DECREF(v);
          skip_decref_v:
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case INPLACE_SUBTRACT:
            w = POP();
            v = TOP();
            if (PyInt_CheckExact(v) && PyInt_CheckExact(w)) {
                /* INLINE: int - int */
                register long a, b, i;
                a = PyInt_AS_LONG(v);
                b = PyInt_AS_LONG(w);
                i = a - b;
                if ((i^a) < 0 && (i^~b) < 0)
                    goto slow_isub;
                x = PyInt_FromLong(i);
            }
            else {
              slow_isub:
                x = PyNumber_InPlaceSubtract(v, w);
            }
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case INPLACE_LSHIFT:
            w = POP();
            v = TOP();
            x = PyNumber_InPlaceLshift(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case INPLACE_RSHIFT:
            w = POP();
            v = TOP();
            x = PyNumber_InPlaceRshift(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case INPLACE_AND:
            w = POP();
            v = TOP();
            x = PyNumber_InPlaceAnd(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case INPLACE_XOR:
            w = POP();
            v = TOP();
            x = PyNumber_InPlaceXor(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case INPLACE_OR:
            w = POP();
            v = TOP();
            x = PyNumber_InPlaceOr(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case SLICE+0:
        case SLICE+1:
        case SLICE+2:
        case SLICE+3:
            if ((opcode-SLICE) & 2)
                w = POP();
            else
                w = NULL;
            if ((opcode-SLICE) & 1)
                v = POP();
            else
                v = NULL;
            u = TOP();
            x = apply_slice(u, v, w);
            Py_DECREF(u);
            Py_XDECREF(v);
            Py_XDECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case STORE_SLICE+0:
        case STORE_SLICE+1:
        case STORE_SLICE+2:
        case STORE_SLICE+3:
            if ((opcode-STORE_SLICE) & 2)
                w = POP();
            else
                w = NULL;
            if ((opcode-STORE_SLICE) & 1)
                v = POP();
            else
                v = NULL;
            u = POP();
            t = POP();
            err = assign_slice(u, v, w, t); /* u[v:w] = t */
            Py_DECREF(t);
            Py_DECREF(u);
            Py_XDECREF(v);
            Py_XDECREF(w);
            if (err == 0) continue;
            break;

        case DELETE_SLICE+0:
        case DELETE_SLICE+1:
        case DELETE_SLICE+2:
        case DELETE_SLICE+3:
            if ((opcode-DELETE_SLICE) & 2)
                w = POP();
            else
                w = NULL;
            if ((opcode-DELETE_SLICE) & 1)
                v = POP();
            else
                v = NULL;
            u = POP();
            err = assign_slice(u, v, w, (PyObject *)NULL);
                                            /* del u[v:w] */
            Py_DECREF(u);
            Py_XDECREF(v);
            Py_XDECREF(w);
            if (err == 0) continue;
            break;

        case STORE_SUBSCR:
            w = TOP();
            v = SECOND();
            u = THIRD();
            STACKADJ(-3);
            /* v[w] = u */
            err = PyObject_SetItem(v, w, u);
            Py_DECREF(u);
            Py_DECREF(v);
            Py_DECREF(w);
            if (err == 0) continue;
            break;

        case DELETE_SUBSCR:
            w = TOP();
            v = SECOND();
            STACKADJ(-2);
            /* del v[w] */
            err = PyObject_DelItem(v, w);
            Py_DECREF(v);
            Py_DECREF(w);
            if (err == 0) continue;
            break;

        case PRINT_EXPR:
            v = POP();
            w = PySys_GetObject("displayhook");
            if (w == NULL) {
                PyErr_SetString(PyExc_RuntimeError,
                                "lost sys.displayhook");
                err = -1;
                x = NULL;
            }
            if (err == 0) {
                x = PyTuple_Pack(1, v);
                if (x == NULL)
                    err = -1;
            }
            if (err == 0) {
                w = PyEval_CallObject(w, x);
                Py_XDECREF(w);
                if (w == NULL)
                    err = -1;
            }
            Py_DECREF(v);
            Py_XDECREF(x);
            break;

        case PRINT_ITEM_TO:
            w = stream = POP();
            /* fall through to PRINT_ITEM */

        case PRINT_ITEM:
            v = POP();
            if (stream == NULL || stream == Py_None) {
                w = PySys_GetObject("stdout");
                if (w == NULL) {
                    PyErr_SetString(PyExc_RuntimeError,
                                    "lost sys.stdout");
                    err = -1;
                }
            }
            /* PyFile_SoftSpace() can exececute arbitrary code
               if sys.stdout is an instance with a __getattr__.
               If __getattr__ raises an exception, w will
               be freed, so we need to prevent that temporarily. */
            Py_XINCREF(w);
            if (w != NULL && PyFile_SoftSpace(w, 0))
                err = PyFile_WriteString(" ", w);
            if (err == 0)
                err = PyFile_WriteObject(v, w, Py_PRINT_RAW);
            if (err == 0) {
                /* XXX move into writeobject() ? */
                if (PyString_Check(v)) {
                    char *s = PyString_AS_STRING(v);
                    Py_ssize_t len = PyString_GET_SIZE(v);
                    if (len == 0 ||
                        !isspace(Py_CHARMASK(s[len-1])) ||
                        s[len-1] == ' ')
                        PyFile_SoftSpace(w, 1);
                }
#ifdef Py_USING_UNICODE
                else if (PyUnicode_Check(v)) {
                    Py_UNICODE *s = PyUnicode_AS_UNICODE(v);
                    Py_ssize_t len = PyUnicode_GET_SIZE(v);
                    if (len == 0 ||
                        !Py_UNICODE_ISSPACE(s[len-1]) ||
                        s[len-1] == ' ')
                        PyFile_SoftSpace(w, 1);
                }
#endif
                else
                    PyFile_SoftSpace(w, 1);
            }
            Py_XDECREF(w);
            Py_DECREF(v);
            Py_XDECREF(stream);
            stream = NULL;
            if (err == 0)
                continue;
            break;

        case PRINT_NEWLINE_TO:
            w = stream = POP();
            /* fall through to PRINT_NEWLINE */

        case PRINT_NEWLINE:
            if (stream == NULL || stream == Py_None) {
                w = PySys_GetObject("stdout");
                if (w == NULL) {
                    PyErr_SetString(PyExc_RuntimeError,
                                    "lost sys.stdout");
                    why = WHY_EXCEPTION;
                }
            }
            if (w != NULL) {
                /* w.write() may replace sys.stdout, so we
                 * have to keep our reference to it */
                Py_INCREF(w);
                err = PyFile_WriteString("\n", w);
                if (err == 0)
                    PyFile_SoftSpace(w, 0);
                Py_DECREF(w);
            }
            Py_XDECREF(stream);
            stream = NULL;
            break;


#ifdef CASE_TOO_BIG
        default: switch (opcode) {
#endif
        case RAISE_VARARGS:
            u = v = w = NULL;
            switch (oparg) {
            case 3:
                u = POP(); /* traceback */
                /* Fallthrough */
            case 2:
                v = POP(); /* value */
                /* Fallthrough */
            case 1:
                w = POP(); /* exc */
            case 0: /* Fallthrough */
                why = do_raise(w, v, u);
                break;
            default:
                PyErr_SetString(PyExc_SystemError,
                           "bad RAISE_VARARGS oparg");
                why = WHY_EXCEPTION;
                break;
            }
            break;

        case LOAD_LOCALS:
            if ((x = f->f_locals) != NULL) {
                Py_INCREF(x);
                PUSH(x);
                continue;
            }
            PyErr_SetString(PyExc_SystemError, "no locals");
            break;

        case RETURN_VALUE:
            retval = POP();
            why = WHY_RETURN;
            goto fast_block_end;

        case YIELD_VALUE:
            retval = POP();
            f->f_stacktop = stack_pointer;
            why = WHY_YIELD;
            goto fast_yield;

        case EXEC_STMT:
            w = TOP();
            v = SECOND();
            u = THIRD();
            STACKADJ(-3);
            READ_TIMESTAMP(intr0);
            err = exec_statement(f, u, v, w);
            READ_TIMESTAMP(intr1);
            Py_DECREF(u);
            Py_DECREF(v);
            Py_DECREF(w);
            break;

        case POP_BLOCK:
            {
                PyTryBlock *b = PyFrame_BlockPop(f);
                while (STACK_LEVEL() > b->b_level) {
                    v = POP();
                    Py_DECREF(v);
                }
            }
            continue;

        PREDICTED(END_FINALLY);
        case END_FINALLY:
            v = POP();
            if (PyInt_Check(v)) {
                why = (enum why_code) PyInt_AS_LONG(v);
                assert(why != WHY_YIELD);
                if (why == WHY_RETURN ||
                    why == WHY_CONTINUE)
                    retval = POP();
            }
            else if (PyExceptionClass_Check(v) ||
                     PyString_Check(v)) {
                w = POP();
                u = POP();
                PyErr_Restore(v, w, u);
                why = WHY_RERAISE;
                break;
            }
            else if (v != Py_None) {
                PyErr_SetString(PyExc_SystemError,
                    "'finally' pops bad exception");
                why = WHY_EXCEPTION;
            }
            Py_DECREF(v);
            break;

        case BUILD_CLASS:
            u = TOP();
            v = SECOND();
            w = THIRD();
            STACKADJ(-2);
            x = build_class(u, v, w);
            SET_TOP(x);
            Py_DECREF(u);
            Py_DECREF(v);
            Py_DECREF(w);
            break;

        case STORE_NAME:
            w = GETITEM(names, oparg);
            v = POP();
            if ((x = f->f_locals) != NULL) {
                if (PyDict_CheckExact(x))
                    err = PyDict_SetItem(x, w, v);
                else
                    err = PyObject_SetItem(x, w, v);
                Py_DECREF(v);
                if (err == 0) continue;
                break;
            }
            t = PyObject_Repr(w);
            if (t == NULL)
                break;
            PyErr_Format(PyExc_SystemError,
                         "no locals found when storing %s",
                         PyString_AS_STRING(t));
            Py_DECREF(t);
            break;

        case DELETE_NAME:
            w = GETITEM(names, oparg);
            if ((x = f->f_locals) != NULL) {
                if ((err = PyObject_DelItem(x, w)) != 0)
                    format_exc_check_arg(PyExc_NameError,
                                         NAME_ERROR_MSG,
                                         w);
                break;
            }
            t = PyObject_Repr(w);
            if (t == NULL)
                break;
            PyErr_Format(PyExc_SystemError,
                         "no locals when deleting %s",
                         PyString_AS_STRING(w));
            Py_DECREF(t);
            break;

        PREDICTED_WITH_ARG(UNPACK_SEQUENCE);
        case UNPACK_SEQUENCE:
            v = POP();
            if (PyTuple_CheckExact(v) &&
                PyTuple_GET_SIZE(v) == oparg) {
                PyObject **items = \
                    ((PyTupleObject *)v)->ob_item;
                while (oparg--) {
                    w = items[oparg];
                    Py_INCREF(w);
                    PUSH(w);
                }
                Py_DECREF(v);
                continue;
            } else if (PyList_CheckExact(v) &&
                       PyList_GET_SIZE(v) == oparg) {
                PyObject **items = \
                    ((PyListObject *)v)->ob_item;
                while (oparg--) {
                    w = items[oparg];
                    Py_INCREF(w);
                    PUSH(w);
                }
            } else if (unpack_iterable(v, oparg,
                                       stack_pointer + oparg)) {
                STACKADJ(oparg);
            } else {
                /* unpack_iterable() raised an exception */
                why = WHY_EXCEPTION;
            }
            Py_DECREF(v);
            break;

        case STORE_ATTR:
            w = GETITEM(names, oparg);
            v = TOP();
            u = SECOND();
            STACKADJ(-2);
            err = PyObject_SetAttr(v, w, u); /* v.w = u */
            Py_DECREF(v);
            Py_DECREF(u);
            if (err == 0) continue;
            break;

        case DELETE_ATTR:
            w = GETITEM(names, oparg);
            v = POP();
            err = PyObject_SetAttr(v, w, (PyObject *)NULL);
                                            /* del v.w */
            Py_DECREF(v);
            break;

        case STORE_GLOBAL:
            w = GETITEM(names, oparg);
            v = POP();
            err = PyDict_SetItem(f->f_globals, w, v);
            Py_DECREF(v);
            if (err == 0) continue;
            break;

        case DELETE_GLOBAL:
            w = GETITEM(names, oparg);
            if ((err = PyDict_DelItem(f->f_globals, w)) != 0)
                format_exc_check_arg(
                    PyExc_NameError, GLOBAL_NAME_ERROR_MSG, w);
            break;

        case LOAD_NAME:
            w = GETITEM(names, oparg);
            if ((v = f->f_locals) == NULL) {
                why = WHY_EXCEPTION;
                t = PyObject_Repr(w);
                if (t == NULL)
                    break;
                PyErr_Format(PyExc_SystemError,
                             "no locals when loading %s",
                             PyString_AS_STRING(w));
                Py_DECREF(t);
                break;
            }
            if (PyDict_CheckExact(v)) {
                x = PyDict_GetItem(v, w);
                Py_XINCREF(x);
            }
            else {
                x = PyObject_GetItem(v, w);
                if (x == NULL && PyErr_Occurred()) {
                    if (!PyErr_ExceptionMatches(
                                    PyExc_KeyError))
                        break;
                    PyErr_Clear();
                }
            }
            if (x == NULL) {
                x = PyDict_GetItem(f->f_globals, w);
                if (x == NULL) {
                    x = PyDict_GetItem(f->f_builtins, w);
                    if (x == NULL) {
                        format_exc_check_arg(
                                    PyExc_NameError,
                                    NAME_ERROR_MSG, w);
                        break;
                    }
                }
                Py_INCREF(x);
            }
            PUSH(x);
            continue;

        case LOAD_GLOBAL:
            w = GETITEM(names, oparg);
            if (PyString_CheckExact(w)) {
                /* Inline the PyDict_GetItem() calls.
                   WARNING: this is an extreme speed hack.
                   Do not try this at home. */
                long hash = ((PyStringObject *)w)->ob_shash;
                if (hash != -1) {
                    PyDictObject *d;
                    PyDictEntry *e;
                    d = (PyDictObject *)(f->f_globals);
                    e = d->ma_lookup(d, w, hash);
                    if (e == NULL) {
                        x = NULL;
                        break;
                    }
                    x = e->me_value;
                    if (x != NULL) {
                        Py_INCREF(x);
                        PUSH(x);
                        continue;
                    }
                    d = (PyDictObject *)(f->f_builtins);
                    e = d->ma_lookup(d, w, hash);
                    if (e == NULL) {
                        x = NULL;
                        break;
                    }
                    x = e->me_value;
                    if (x != NULL) {
                        Py_INCREF(x);
                        PUSH(x);
                        continue;
                    }
                    goto load_global_error;
                }
            }
            /* This is the un-inlined version of the code above */
            x = PyDict_GetItem(f->f_globals, w);
            if (x == NULL) {
                x = PyDict_GetItem(f->f_builtins, w);
                if (x == NULL) {
                  load_global_error:
                    format_exc_check_arg(
                                PyExc_NameError,
                                GLOBAL_NAME_ERROR_MSG, w);
                    break;
                }
            }
            Py_INCREF(x);
            PUSH(x);
            continue;

        case DELETE_FAST:
            x = GETLOCAL(oparg);
            if (x != NULL) {
                SETLOCAL(oparg, NULL);
                continue;
            }
            format_exc_check_arg(
                PyExc_UnboundLocalError,
                UNBOUNDLOCAL_ERROR_MSG,
                PyTuple_GetItem(co->co_varnames, oparg)
                );
            break;

        case LOAD_CLOSURE:
            x = freevars[oparg];
            Py_INCREF(x);
            PUSH(x);
            if (x != NULL) continue;
            break;

        case LOAD_DEREF:
            x = freevars[oparg];
            w = PyCell_Get(x);
            if (w != NULL) {
                PUSH(w);
                continue;
            }
            err = -1;
            /* Don't stomp existing exception */
            if (PyErr_Occurred())
                break;
            if (oparg < PyTuple_GET_SIZE(co->co_cellvars)) {
                v = PyTuple_GET_ITEM(co->co_cellvars,
                                     oparg);
                format_exc_check_arg(
                       PyExc_UnboundLocalError,
                       UNBOUNDLOCAL_ERROR_MSG,
                       v);
            } else {
                v = PyTuple_GET_ITEM(co->co_freevars, oparg -
                    PyTuple_GET_SIZE(co->co_cellvars));
                format_exc_check_arg(PyExc_NameError,
                                     UNBOUNDFREE_ERROR_MSG, v);
            }
            break;

        case STORE_DEREF:
            w = POP();
            x = freevars[oparg];
            PyCell_Set(x, w);
            Py_DECREF(w);
            continue;

        case BUILD_TUPLE:
            x = PyTuple_New(oparg);
            if (x != NULL) {
                for (; --oparg >= 0;) {
                    w = POP();
                    PyTuple_SET_ITEM(x, oparg, w);
                }
                PUSH(x);
                continue;
            }
            break;

        case BUILD_LIST:
            x =  PyList_New(oparg);
            if (x != NULL) {
                for (; --oparg >= 0;) {
                    w = POP();
                    PyList_SET_ITEM(x, oparg, w);
                }
                PUSH(x);
                continue;
            }
            break;

        case BUILD_SET:
            x = PySet_New(NULL);
            if (x != NULL) {
                for (; --oparg >= 0;) {
                    w = POP();
                    if (err == 0)
                        err = PySet_Add(x, w);
                    Py_DECREF(w);
                }
                if (err != 0) {
                    Py_DECREF(x);
                    break;
                }
                PUSH(x);
                continue;
            }
            break;


        case BUILD_MAP:
            x = _PyDict_NewPresized((Py_ssize_t)oparg);
            PUSH(x);
            if (x != NULL) continue;
            break;

        case STORE_MAP:
            w = TOP();     /* key */
            u = SECOND();  /* value */
            v = THIRD();   /* dict */
            STACKADJ(-2);
            assert (PyDict_CheckExact(v));
            err = PyDict_SetItem(v, w, u);  /* v[w] = u */
            Py_DECREF(u);
            Py_DECREF(w);
            if (err == 0) continue;
            break;

        case MAP_ADD:
            w = TOP();     /* key */
            u = SECOND();  /* value */
            STACKADJ(-2);
            v = stack_pointer[-oparg];  /* dict */
            assert (PyDict_CheckExact(v));
            err = PyDict_SetItem(v, w, u);  /* v[w] = u */
            Py_DECREF(u);
            Py_DECREF(w);
            if (err == 0) {
                PREDICT(JUMP_ABSOLUTE);
                continue;
            }
            break;

        case LOAD_ATTR:
            w = GETITEM(names, oparg);
            v = TOP();
            x = PyObject_GetAttr(v, w);
            Py_DECREF(v);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case COMPARE_OP:
            w = POP();
            v = TOP();
            if (PyInt_CheckExact(w) && PyInt_CheckExact(v)) {
                /* INLINE: cmp(int, int) */
                register long a, b;
                register int res;
                a = PyInt_AS_LONG(v);
                b = PyInt_AS_LONG(w);
                switch (oparg) {
                case PyCmp_LT: res = a <  b; break;
                case PyCmp_LE: res = a <= b; break;
                case PyCmp_EQ: res = a == b; break;
                case PyCmp_NE: res = a != b; break;
                case PyCmp_GT: res = a >  b; break;
                case PyCmp_GE: res = a >= b; break;
                case PyCmp_IS: res = v == w; break;
                case PyCmp_IS_NOT: res = v != w; break;
                default: goto slow_compare;
                }
                x = res ? Py_True : Py_False;
                Py_INCREF(x);
            }
            else {
              slow_compare:
                x = cmp_outcome(oparg, v, w);
            }
            Py_DECREF(v);
            Py_DECREF(w);
            SET_TOP(x);
            if (x == NULL) break;
            PREDICT(POP_JUMP_IF_FALSE);
            PREDICT(POP_JUMP_IF_TRUE);
            continue;

        case IMPORT_NAME:
            w = GETITEM(names, oparg);
            x = PyDict_GetItemString(f->f_builtins, "__import__");
            if (x == NULL) {
                PyErr_SetString(PyExc_ImportError,
                                "__import__ not found");
                break;
            }
            Py_INCREF(x);
            v = POP();
            u = TOP();
            if (PyInt_AsLong(u) != -1 || PyErr_Occurred())
                w = PyTuple_Pack(5,
                            w,
                            f->f_globals,
                            f->f_locals == NULL ?
                                  Py_None : f->f_locals,
                            v,
                            u);
            else
                w = PyTuple_Pack(4,
                            w,
                            f->f_globals,
                            f->f_locals == NULL ?
                                  Py_None : f->f_locals,
                            v);
            Py_DECREF(v);
            Py_DECREF(u);
            if (w == NULL) {
                u = POP();
                Py_DECREF(x);
                x = NULL;
                break;
            }
            READ_TIMESTAMP(intr0);
            v = x;
            x = PyEval_CallObject(v, w);
            Py_DECREF(v);
            READ_TIMESTAMP(intr1);
            Py_DECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case IMPORT_STAR:
            v = POP();
            PyFrame_FastToLocals(f);
            if ((x = f->f_locals) == NULL) {
                PyErr_SetString(PyExc_SystemError,
                    "no locals found during 'import *'");
                break;
            }
            READ_TIMESTAMP(intr0);
            err = import_all_from(x, v);
            READ_TIMESTAMP(intr1);
            PyFrame_LocalsToFast(f, 0);
            Py_DECREF(v);
            if (err == 0) continue;
            break;

        case IMPORT_FROM:
            w = GETITEM(names, oparg);
            v = TOP();
            READ_TIMESTAMP(intr0);
            x = import_from(v, w);
            READ_TIMESTAMP(intr1);
            PUSH(x);
            if (x != NULL) continue;
            break;

        case JUMP_FORWARD:
            JUMPBY(oparg);
            goto fast_next_opcode;

        PREDICTED_WITH_ARG(POP_JUMP_IF_FALSE);
        case POP_JUMP_IF_FALSE:
            w = POP();
            if (w == Py_True) {
                Py_DECREF(w);
                goto fast_next_opcode;
            }
            if (w == Py_False) {
                Py_DECREF(w);
                JUMPTO(oparg);
                goto fast_next_opcode;
            }
            err = PyObject_IsTrue(w);
            Py_DECREF(w);
            if (err > 0)
                err = 0;
            else if (err == 0)
                JUMPTO(oparg);
            else
                break;
            continue;

        PREDICTED_WITH_ARG(POP_JUMP_IF_TRUE);
        case POP_JUMP_IF_TRUE:
            w = POP();
            if (w == Py_False) {
                Py_DECREF(w);
                goto fast_next_opcode;
            }
            if (w == Py_True) {
                Py_DECREF(w);
                JUMPTO(oparg);
                goto fast_next_opcode;
            }
            err = PyObject_IsTrue(w);
            Py_DECREF(w);
            if (err > 0) {
                err = 0;
                JUMPTO(oparg);
            }
            else if (err == 0)
                ;
            else
                break;
            continue;

        case JUMP_IF_FALSE_OR_POP:
            w = TOP();
            if (w == Py_True) {
                STACKADJ(-1);
                Py_DECREF(w);
                goto fast_next_opcode;
            }
            if (w == Py_False) {
                JUMPTO(oparg);
                goto fast_next_opcode;
            }
            err = PyObject_IsTrue(w);
            if (err > 0) {
                STACKADJ(-1);
                Py_DECREF(w);
                err = 0;
            }
            else if (err == 0)
                JUMPTO(oparg);
            else
                break;
            continue;

        case JUMP_IF_TRUE_OR_POP:
            w = TOP();
            if (w == Py_False) {
                STACKADJ(-1);
                Py_DECREF(w);
                goto fast_next_opcode;
            }
            if (w == Py_True) {
                JUMPTO(oparg);
                goto fast_next_opcode;
            }
            err = PyObject_IsTrue(w);
            if (err > 0) {
                err = 0;
                JUMPTO(oparg);
            }
            else if (err == 0) {
                STACKADJ(-1);
                Py_DECREF(w);
            }
            else
                break;
            continue;

        PREDICTED_WITH_ARG(JUMP_ABSOLUTE);
        case JUMP_ABSOLUTE:
            JUMPTO(oparg);
#if FAST_LOOPS
            /* Enabling this path speeds-up all while and for-loops by bypassing
               the per-loop checks for signals.  By default, this should be turned-off
               because it prevents detection of a control-break in tight loops like
               "while 1: pass".  Compile with this option turned-on when you need
               the speed-up and do not need break checking inside tight loops (ones
               that contain only instructions ending with goto fast_next_opcode).
            */
            goto fast_next_opcode;
#else
            continue;
#endif

        case GET_ITER:
            /* before: [obj]; after [getiter(obj)] */
            v = TOP();
            x = PyObject_GetIter(v);
            Py_DECREF(v);
            if (x != NULL) {
                SET_TOP(x);
                PREDICT(FOR_ITER);
                continue;
            }
            STACKADJ(-1);
            break;

        PREDICTED_WITH_ARG(FOR_ITER);
        case FOR_ITER:
            /* before: [iter]; after: [iter, iter()] *or* [] */
            v = TOP();
            x = (*v->ob_type->tp_iternext)(v);
            if (x != NULL) {
                PUSH(x);
                PREDICT(STORE_FAST);
                PREDICT(UNPACK_SEQUENCE);
                continue;
            }
            if (PyErr_Occurred()) {
                if (!PyErr_ExceptionMatches(
                                PyExc_StopIteration))
                    break;
                PyErr_Clear();
            }
            /* iterator ended normally */
            x = v = POP();
            Py_DECREF(v);
            JUMPBY(oparg);
            continue;

        case BREAK_LOOP:
            why = WHY_BREAK;
            goto fast_block_end;

        case CONTINUE_LOOP:
            retval = PyInt_FromLong(oparg);
            if (!retval) {
                x = NULL;
                break;
            }
            why = WHY_CONTINUE;
            goto fast_block_end;

        case SETUP_LOOP:
        case SETUP_EXCEPT:
        case SETUP_FINALLY:
            /* NOTE: If you add any new block-setup opcodes that
               are not try/except/finally handlers, you may need
               to update the PyGen_NeedsFinalizing() function.
               */

            PyFrame_BlockSetup(f, opcode, INSTR_OFFSET() + oparg,
                               STACK_LEVEL());
            continue;

        case SETUP_WITH:
        {
            static PyObject *exit, *enter;
            w = TOP();
            x = special_lookup(w, "__exit__", &exit);
            if (!x)
                break;
            SET_TOP(x);
            u = special_lookup(w, "__enter__", &enter);
            Py_DECREF(w);
            if (!u) {
                x = NULL;
                break;
            }
            x = PyObject_CallFunctionObjArgs(u, NULL);
            Py_DECREF(u);
            if (!x)
                break;
            /* Setup a finally block (SETUP_WITH as a block is
               equivalent to SETUP_FINALLY except it normalizes
               the exception) before pushing the result of
               __enter__ on the stack. */
            PyFrame_BlockSetup(f, SETUP_WITH, INSTR_OFFSET() + oparg,
                               STACK_LEVEL());

            PUSH(x);
            continue;
        }

        case WITH_CLEANUP:
        {
            /* At the top of the stack are 1-3 values indicating
               how/why we entered the finally clause:
               - TOP = None
               - (TOP, SECOND) = (WHY_{RETURN,CONTINUE}), retval
               - TOP = WHY_*; no retval below it
               - (TOP, SECOND, THIRD) = exc_info()
               Below them is EXIT, the context.__exit__ bound method.
               In the last case, we must call
                 EXIT(TOP, SECOND, THIRD)
               otherwise we must call
                 EXIT(None, None, None)

               In all cases, we remove EXIT from the stack, leaving
               the rest in the same order.

               In addition, if the stack represents an exception,
               *and* the function call returns a 'true' value, we
               "zap" this information, to prevent END_FINALLY from
               re-raising the exception.  (But non-local gotos
               should still be resumed.)
            */

            PyObject *exit_func;

            u = POP();
            if (u == Py_None) {
                exit_func = TOP();
                SET_TOP(u);
                v = w = Py_None;
            }
            else if (PyInt_Check(u)) {
                switch(PyInt_AS_LONG(u)) {
                case WHY_RETURN:
                case WHY_CONTINUE:
                    /* Retval in TOP. */
                    exit_func = SECOND();
                    SET_SECOND(TOP());
                    SET_TOP(u);
                    break;
                default:
                    exit_func = TOP();
                    SET_TOP(u);
                    break;
                }
                u = v = w = Py_None;
            }
            else {
                v = TOP();
                w = SECOND();
                exit_func = THIRD();
                SET_TOP(u);
                SET_SECOND(v);
                SET_THIRD(w);
            }
            /* XXX Not the fastest way to call it... */
            x = PyObject_CallFunctionObjArgs(exit_func, u, v, w,
                                             NULL);
            Py_DECREF(exit_func);
            if (x == NULL)
                break; /* Go to error exit */

            if (u != Py_None)
                err = PyObject_IsTrue(x);
            else
                err = 0;
            Py_DECREF(x);

            if (err < 0)
                break; /* Go to error exit */
            else if (err > 0) {
                err = 0;
                /* There was an exception and a true return */
                STACKADJ(-2);
                Py_INCREF(Py_None);
                SET_TOP(Py_None);
                Py_DECREF(u);
                Py_DECREF(v);
                Py_DECREF(w);
            } else {
                /* The stack was rearranged to remove EXIT
                   above. Let END_FINALLY do its thing */
            }
            PREDICT(END_FINALLY);
            break;
        }

        case CALL_FUNCTION:
        {
            PyObject **sp;
            PCALL(PCALL_ALL);
            sp = stack_pointer;
#ifdef WITH_TSC
            x = call_function(&sp, oparg, &intr0, &intr1);
#else
            x = call_function(&sp, oparg);
#endif
            stack_pointer = sp;
            PUSH(x);
            if (x != NULL)
                continue;
            break;
        }

        case CALL_FUNCTION_VAR:
        case CALL_FUNCTION_KW:
        case CALL_FUNCTION_VAR_KW:
        {
            int na = oparg & 0xff;
            int nk = (oparg>>8) & 0xff;
            int flags = (opcode - CALL_FUNCTION) & 3;
            int n = na + 2 * nk;
            PyObject **pfunc, *func, **sp;
            PCALL(PCALL_ALL);
            if (flags & CALL_FLAG_VAR)
                n++;
            if (flags & CALL_FLAG_KW)
                n++;
            pfunc = stack_pointer - n - 1;
            func = *pfunc;

            if (PyMethod_Check(func)
                && PyMethod_GET_SELF(func) != NULL) {
                PyObject *self = PyMethod_GET_SELF(func);
                Py_INCREF(self);
                func = PyMethod_GET_FUNCTION(func);
                Py_INCREF(func);
                Py_DECREF(*pfunc);
                *pfunc = self;
                na++;
            } else
                Py_INCREF(func);
            sp = stack_pointer;
            READ_TIMESTAMP(intr0);
            x = ext_do_call(func, &sp, flags, na, nk);
            READ_TIMESTAMP(intr1);
            stack_pointer = sp;
            Py_DECREF(func);

            while (stack_pointer > pfunc) {
                w = POP();
                Py_DECREF(w);
            }
            PUSH(x);
            if (x != NULL)
                continue;
            break;
        }

        case MAKE_FUNCTION:
            v = POP(); /* code object */
            x = PyFunction_New(v, f->f_globals);
            Py_DECREF(v);
            /* XXX Maybe this should be a separate opcode? */
            if (x != NULL && oparg > 0) {
                v = PyTuple_New(oparg);
                if (v == NULL) {
                    Py_DECREF(x);
                    x = NULL;
                    break;
                }
                while (--oparg >= 0) {
                    w = POP();
                    PyTuple_SET_ITEM(v, oparg, w);
                }
                err = PyFunction_SetDefaults(x, v);
                Py_DECREF(v);
            }
            PUSH(x);
            break;

        case MAKE_CLOSURE:
        {
            v = POP(); /* code object */
            x = PyFunction_New(v, f->f_globals);
            Py_DECREF(v);
            if (x != NULL) {
                v = POP();
                if (PyFunction_SetClosure(x, v) != 0) {
                    /* Can't happen unless bytecode is corrupt. */
                    why = WHY_EXCEPTION;
                }
                Py_DECREF(v);
            }
            if (x != NULL && oparg > 0) {
                v = PyTuple_New(oparg);
                if (v == NULL) {
                    Py_DECREF(x);
                    x = NULL;
                    break;
                }
                while (--oparg >= 0) {
                    w = POP();
                    PyTuple_SET_ITEM(v, oparg, w);
                }
                if (PyFunction_SetDefaults(x, v) != 0) {
                    /* Can't happen unless
                       PyFunction_SetDefaults changes. */
                    why = WHY_EXCEPTION;
                }
                Py_DECREF(v);
            }
            PUSH(x);
            break;
        }

        case BUILD_SLICE:
            if (oparg == 3)
                w = POP();
            else
                w = NULL;
            v = POP();
            u = TOP();
            x = PySlice_New(u, v, w);
            Py_DECREF(u);
            Py_DECREF(v);
            Py_XDECREF(w);
            SET_TOP(x);
            if (x != NULL) continue;
            break;

        case EXTENDED_ARG:
            opcode = NEXTOP();
            oparg = oparg<<16 | NEXTARG();
            goto dispatch_opcode;

        default:
            fprintf(stderr,
                "XXX lineno: %d, opcode: %d\n",
                PyFrame_GetLineNumber(f),
                opcode);
            PyErr_SetString(PyExc_SystemError, "unknown opcode");
            why = WHY_EXCEPTION;
            break;

#ifdef CASE_TOO_BIG
        }
#endif

        } /* switch */

        on_error:

        READ_TIMESTAMP(inst1);

        /* Quickly continue if no error occurred */

        if (why == WHY_NOT) {
            if (err == 0 && x != NULL) {
#ifdef CHECKEXC
                /* This check is expensive! */
                if (PyErr_Occurred())
                    fprintf(stderr,
                        "XXX undetected error\n");
                else {
#endif
                    READ_TIMESTAMP(loop1);
                    continue; /* Normal, fast path */
#ifdef CHECKEXC
                }
#endif
            }
            why = WHY_EXCEPTION;
            x = Py_None;
            err = 0;
        }

        /* Double-check exception status */

        if (why == WHY_EXCEPTION || why == WHY_RERAISE) {
            if (!PyErr_Occurred()) {
                PyErr_SetString(PyExc_SystemError,
                    "error return without exception set");
                why = WHY_EXCEPTION;
            }
        }
#ifdef CHECKEXC
        else {
            /* This check is expensive! */
            if (PyErr_Occurred()) {
                char buf[128];
                sprintf(buf, "Stack unwind with exception "
                    "set and why=%d", why);
                Py_FatalError(buf);
            }
        }
#endif

        /* Log traceback info if this is a real exception */

        if (why == WHY_EXCEPTION) {
            PyTraceBack_Here(f);

            if (tstate->c_tracefunc != NULL)
                call_exc_trace(tstate->c_tracefunc,
                               tstate->c_traceobj, f);
        }

        /* For the rest, treat WHY_RERAISE as WHY_EXCEPTION */

        if (why == WHY_RERAISE)
            why = WHY_EXCEPTION;

        /* Unwind stacks if a (pseudo) exception occurred */

fast_block_end:
        while (why != WHY_NOT && f->f_iblock > 0) {
            /* Peek at the current block. */
            PyTryBlock *b = &f->f_blockstack[f->f_iblock - 1];

            assert(why != WHY_YIELD);
            if (b->b_type == SETUP_LOOP && why == WHY_CONTINUE) {
                why = WHY_NOT;
                JUMPTO(PyInt_AS_LONG(retval));
                Py_DECREF(retval);
                break;
            }

            /* Now we have to pop the block. */
            f->f_iblock--;

            while (STACK_LEVEL() > b->b_level) {
                v = POP();
                Py_XDECREF(v);
            }
            if (b->b_type == SETUP_LOOP && why == WHY_BREAK) {
                why = WHY_NOT;
                JUMPTO(b->b_handler);
                break;
            }
            if (b->b_type == SETUP_FINALLY ||
                (b->b_type == SETUP_EXCEPT &&
                 why == WHY_EXCEPTION) ||
                b->b_type == SETUP_WITH) {
                if (why == WHY_EXCEPTION) {
                    PyObject *exc, *val, *tb;
                    PyErr_Fetch(&exc, &val, &tb);
                    if (val == NULL) {
                        val = Py_None;
                        Py_INCREF(val);
                    }
                    /* Make the raw exception data
                       available to the handler,
                       so a program can emulate the
                       Python main loop.  Don't do
                       this for 'finally'. */
                    if (b->b_type == SETUP_EXCEPT ||
                        b->b_type == SETUP_WITH) {
                        PyErr_NormalizeException(
                            &exc, &val, &tb);
                        set_exc_info(tstate,
                                     exc, val, tb);
                    }
                    if (tb == NULL) {
                        Py_INCREF(Py_None);
                        PUSH(Py_None);
                    } else
                        PUSH(tb);
                    PUSH(val);
                    PUSH(exc);
                }
                else {
                    if (why & (WHY_RETURN | WHY_CONTINUE))
                        PUSH(retval);
                    v = PyInt_FromLong((long)why);
                    PUSH(v);
                }
                why = WHY_NOT;
                JUMPTO(b->b_handler);
                break;
            }
        } /* unwind stack */

        /* End the loop if we still have an error (or return) */

        if (why != WHY_NOT)
            break;
        READ_TIMESTAMP(loop1);

    } /* main loop */

    assert(why != WHY_YIELD);
    /* Pop remaining stack entries. */
    while (!EMPTY()) {
        v = POP();
        Py_XDECREF(v);
    }

    if (why != WHY_RETURN)
        retval = NULL;

fast_yield:
    if (tstate->use_tracing) {
        if (tstate->c_tracefunc) {
            if (why == WHY_RETURN || why == WHY_YIELD) {
                if (call_trace(tstate->c_tracefunc,
                               tstate->c_traceobj, f,
                               PyTrace_RETURN, retval)) {
                    Py_XDECREF(retval);
                    retval = NULL;
                    why = WHY_EXCEPTION;
                }
            }
            else if (why == WHY_EXCEPTION) {
                call_trace_protected(tstate->c_tracefunc,
                                     tstate->c_traceobj, f,
                                     PyTrace_RETURN, NULL);
            }
        }
        if (tstate->c_profilefunc) {
            if (why == WHY_EXCEPTION)
                call_trace_protected(tstate->c_profilefunc,
                                     tstate->c_profileobj, f,
                                     PyTrace_RETURN, NULL);
            else if (call_trace(tstate->c_profilefunc,
                                tstate->c_profileobj, f,
                                PyTrace_RETURN, retval)) {
                Py_XDECREF(retval);
                retval = NULL;
                why = WHY_EXCEPTION;
            }
        }
    }

    if (tstate->frame->f_exc_type != NULL)
        reset_exc_info(tstate);
    else {
        assert(tstate->frame->f_exc_value == NULL);
        assert(tstate->frame->f_exc_traceback == NULL);
    }

    /* pop frame */
exit_eval_frame:
    Py_LeaveRecursiveCall();
    tstate->frame = f->f_back;

    return retval;
}

/* This is gonna seem *real weird*, but if you put some other code between
   PyEval_EvalFrame() and PyEval_EvalCodeEx() you will need to adjust
   the test in the if statements in Misc/gdbinit (pystack and pystackv). */

PyObject *
PyEval_EvalCodeEx(PyCodeObject *co, PyObject *globals, PyObject *locals,
           PyObject **args, int argcount, PyObject **kws, int kwcount,
           PyObject **defs, int defcount, PyObject *closure)
{
    register PyFrameObject *f;
    register PyObject *retval = NULL;
    register PyObject **fastlocals, **freevars;
    PyThreadState *tstate = PyThreadState_GET();
    PyObject *x, *u;

    if (globals == NULL) {
        PyErr_SetString(PyExc_SystemError,
                        "PyEval_EvalCodeEx: NULL globals");
        return NULL;
    }

    assert(tstate != NULL);
    assert(globals != NULL);
    f = PyFrame_New(tstate, co, globals, locals);
    if (f == NULL)
        return NULL;

    fastlocals = f->f_localsplus;
    freevars = f->f_localsplus + co->co_nlocals;

    if (co->co_argcount > 0 ||
        co->co_flags & (CO_VARARGS | CO_VARKEYWORDS)) {
        int i;
        int n = argcount;
        PyObject *kwdict = NULL;
        if (co->co_flags & CO_VARKEYWORDS) {
            kwdict = PyDict_New();
            if (kwdict == NULL)
                goto fail;
            i = co->co_argcount;
            if (co->co_flags & CO_VARARGS)
                i++;
            SETLOCAL(i, kwdict);
        }
        if (argcount > co->co_argcount) {
            if (!(co->co_flags & CO_VARARGS)) {
                PyErr_Format(PyExc_TypeError,
                    "%.200s() takes %s %d "
                    "argument%s (%d given)",
                    PyString_AsString(co->co_name),
                    defcount ? "at most" : "exactly",
                    co->co_argcount,
                    co->co_argcount == 1 ? "" : "s",
                    argcount + kwcount);
                goto fail;
            }
            n = co->co_argcount;
        }
        for (i = 0; i < n; i++) {
            x = args[i];
            Py_INCREF(x);
            SETLOCAL(i, x);
        }
        if (co->co_flags & CO_VARARGS) {
            u = PyTuple_New(argcount - n);
            if (u == NULL)
                goto fail;
            SETLOCAL(co->co_argcount, u);
            for (i = n; i < argcount; i++) {
                x = args[i];
                Py_INCREF(x);
                PyTuple_SET_ITEM(u, i-n, x);
            }
        }
        for (i = 0; i < kwcount; i++) {
            PyObject **co_varnames;
            PyObject *keyword = kws[2*i];
            PyObject *value = kws[2*i + 1];
            int j;
            if (keyword == NULL || !(PyString_Check(keyword)
#ifdef Py_USING_UNICODE
                                     || PyUnicode_Check(keyword)
#endif
                        )) {
                PyErr_Format(PyExc_TypeError,
                    "%.200s() keywords must be strings",
                    PyString_AsString(co->co_name));
                goto fail;
            }
            /* Speed hack: do raw pointer compares. As names are
               normally interned this should almost always hit. */
            co_varnames = ((PyTupleObject *)(co->co_varnames))->ob_item;
            for (j = 0; j < co->co_argcount; j++) {
                PyObject *nm = co_varnames[j];
                if (nm == keyword)
                    goto kw_found;
            }
            /* Slow fallback, just in case */
            for (j = 0; j < co->co_argcount; j++) {
                PyObject *nm = co_varnames[j];
                int cmp = PyObject_RichCompareBool(
                    keyword, nm, Py_EQ);
                if (cmp > 0)
                    goto kw_found;
                else if (cmp < 0)
                    goto fail;
            }
            if (kwdict == NULL) {
                PyObject *kwd_str = kwd_as_string(keyword);
                if (kwd_str) {
                    PyErr_Format(PyExc_TypeError,
                                 "%.200s() got an unexpected "
                                 "keyword argument '%.400s'",
                                 PyString_AsString(co->co_name),
                                 PyString_AsString(kwd_str));
                    Py_DECREF(kwd_str);
                }
                goto fail;
            }
            PyDict_SetItem(kwdict, keyword, value);
            continue;
          kw_found:
            if (GETLOCAL(j) != NULL) {
                PyObject *kwd_str = kwd_as_string(keyword);
                if (kwd_str) {
                    PyErr_Format(PyExc_TypeError,
                                 "%.200s() got multiple "
                                 "values for keyword "
                                 "argument '%.400s'",
                                 PyString_AsString(co->co_name),
                                 PyString_AsString(kwd_str));
                    Py_DECREF(kwd_str);
                }
                goto fail;
            }
            Py_INCREF(value);
            SETLOCAL(j, value);
        }
        if (argcount < co->co_argcount) {
            int m = co->co_argcount - defcount;
            for (i = argcount; i < m; i++) {
                if (GETLOCAL(i) == NULL) {
                    int j, given = 0;
                    for (j = 0; j < co->co_argcount; j++)
                        if (GETLOCAL(j))
                            given++;
                    PyErr_Format(PyExc_TypeError,
                        "%.200s() takes %s %d "
                        "argument%s (%d given)",
                        PyString_AsString(co->co_name),
                        ((co->co_flags & CO_VARARGS) ||
                         defcount) ? "at least"
                                   : "exactly",
                        m, m == 1 ? "" : "s", given);
                    goto fail;
                }
            }
            if (n > m)
                i = n - m;
            else
                i = 0;
            for (; i < defcount; i++) {
                if (GETLOCAL(m+i) == NULL) {
                    PyObject *def = defs[i];
                    Py_INCREF(def);
                    SETLOCAL(m+i, def);
                }
            }
        }
    }
    else if (argcount > 0 || kwcount > 0) {
        PyErr_Format(PyExc_TypeError,
                     "%.200s() takes no arguments (%d given)",
                     PyString_AsString(co->co_name),
                     argcount + kwcount);
        goto fail;
    }
    /* Allocate and initialize storage for cell vars, and copy free
       vars into frame.  This isn't too efficient right now. */
    if (PyTuple_GET_SIZE(co->co_cellvars)) {
        int i, j, nargs, found;
        char *cellname, *argname;
        PyObject *c;

        nargs = co->co_argcount;
        if (co->co_flags & CO_VARARGS)
            nargs++;
        if (co->co_flags & CO_VARKEYWORDS)
            nargs++;

        /* Initialize each cell var, taking into account
           cell vars that are initialized from arguments.

           Should arrange for the compiler to put cellvars
           that are arguments at the beginning of the cellvars
           list so that we can march over it more efficiently?
        */
        for (i = 0; i < PyTuple_GET_SIZE(co->co_cellvars); ++i) {
            cellname = PyString_AS_STRING(
                PyTuple_GET_ITEM(co->co_cellvars, i));
            found = 0;
            for (j = 0; j < nargs; j++) {
                argname = PyString_AS_STRING(
                    PyTuple_GET_ITEM(co->co_varnames, j));
                if (strcmp(cellname, argname) == 0) {
                    c = PyCell_New(GETLOCAL(j));
                    if (c == NULL)
                        goto fail;
                    GETLOCAL(co->co_nlocals + i) = c;
                    found = 1;
                    break;
                }
            }
            if (found == 0) {
                c = PyCell_New(NULL);
                if (c == NULL)
                    goto fail;
                SETLOCAL(co->co_nlocals + i, c);
            }
        }
    }
    if (PyTuple_GET_SIZE(co->co_freevars)) {
        int i;
        for (i = 0; i < PyTuple_GET_SIZE(co->co_freevars); ++i) {
            PyObject *o = PyTuple_GET_ITEM(closure, i);
            Py_INCREF(o);
            freevars[PyTuple_GET_SIZE(co->co_cellvars) + i] = o;
        }
    }

    if (co->co_flags & CO_GENERATOR) {
        /* Don't need to keep the reference to f_back, it will be set
         * when the generator is resumed. */
        Py_CLEAR(f->f_back);

        PCALL(PCALL_GENERATOR);

        /* Create a new generator that owns the ready to run frame
         * and return that as the value. */
        return PyGen_New(f);
    }

    retval = PyEval_EvalFrameEx(f,0);

fail: /* Jump here from prelude on failure */

    /* decref'ing the frame can cause __del__ methods to get invoked,
       which can call back into Python.  While we're done with the
       current Python frame (f), the associated C stack is still in use,
       so recursion_depth must be boosted for the duration.
    */
    assert(tstate != NULL);
    ++tstate->recursion_depth;
    Py_DECREF(f);
    --tstate->recursion_depth;
    return retval;
}


static PyObject *
special_lookup(PyObject *o, char *meth, PyObject **cache)
{
    PyObject *res;
    if (PyInstance_Check(o)) {
        if (!*cache)
            return PyObject_GetAttrString(o, meth);
        else
            return PyObject_GetAttr(o, *cache);
    }
    res = _PyObject_LookupSpecial(o, meth, cache);
    if (res == NULL && !PyErr_Occurred()) {
        PyErr_SetObject(PyExc_AttributeError, *cache);
        return NULL;
    }
    return res;
}


static PyObject *
kwd_as_string(PyObject *kwd) {
#ifdef Py_USING_UNICODE
    if (PyString_Check(kwd)) {
#else
        assert(PyString_Check(kwd));
#endif
        Py_INCREF(kwd);
        return kwd;
#ifdef Py_USING_UNICODE
    }
    return _PyUnicode_AsDefaultEncodedString(kwd, "replace");
#endif
}


/* Implementation notes for set_exc_info() and reset_exc_info():

- Below, 'exc_ZZZ' stands for 'exc_type', 'exc_value' and
  'exc_traceback'.  These always travel together.

- tstate->curexc_ZZZ is the "hot" exception that is set by
  PyErr_SetString(), cleared by PyErr_Clear(), and so on.

- Once an exception is caught by an except clause, it is transferred
  from tstate->curexc_ZZZ to tstate->exc_ZZZ, from which sys.exc_info()
  can pick it up.  This is the primary task of set_exc_info().
  XXX That can't be right:  set_exc_info() doesn't look at tstate->curexc_ZZZ.

- Now let me explain the complicated dance with frame->f_exc_ZZZ.

  Long ago, when none of this existed, there were just a few globals:
  one set corresponding to the "hot" exception, and one set
  corresponding to sys.exc_ZZZ.  (Actually, the latter weren't C
  globals; they were simply stored as sys.exc_ZZZ.  For backwards
  compatibility, they still are!)  The problem was that in code like
  this:

     try:
    "something that may fail"
     except "some exception":
    "do something else first"
    "print the exception from sys.exc_ZZZ."

  if "do something else first" invoked something that raised and caught
  an exception, sys.exc_ZZZ were overwritten.  That was a frequent
  cause of subtle bugs.  I fixed this by changing the semantics as
  follows:

    - Within one frame, sys.exc_ZZZ will hold the last exception caught
      *in that frame*.

    - But initially, and as long as no exception is caught in a given
      frame, sys.exc_ZZZ will hold the last exception caught in the
      previous frame (or the frame before that, etc.).

  The first bullet fixed the bug in the above example.  The second
  bullet was for backwards compatibility: it was (and is) common to
  have a function that is called when an exception is caught, and to
  have that function access the caught exception via sys.exc_ZZZ.
  (Example: traceback.print_exc()).

  At the same time I fixed the problem that sys.exc_ZZZ weren't
  thread-safe, by introducing sys.exc_info() which gets it from tstate;
  but that's really a separate improvement.

  The reset_exc_info() function in ceval.c restores the tstate->exc_ZZZ
  variables to what they were before the current frame was called.  The
  set_exc_info() function saves them on the frame so that
  reset_exc_info() can restore them.  The invariant is that
  frame->f_exc_ZZZ is NULL iff the current frame never caught an
  exception (where "catching" an exception applies only to successful
  except clauses); and if the current frame ever caught an exception,
  frame->f_exc_ZZZ is the exception that was stored in tstate->exc_ZZZ
  at the start of the current frame.

*/

static void
set_exc_info(PyThreadState *tstate,
             PyObject *type, PyObject *value, PyObject *tb)
{
    PyFrameObject *frame = tstate->frame;
    PyObject *tmp_type, *tmp_value, *tmp_tb;

    assert(type != NULL);
    assert(frame != NULL);
    if (frame->f_exc_type == NULL) {
        assert(frame->f_exc_value == NULL);
        assert(frame->f_exc_traceback == NULL);
        /* This frame didn't catch an exception before. */
        /* Save previous exception of this thread in this frame. */
        if (tstate->exc_type == NULL) {
            /* XXX Why is this set to Py_None? */
            Py_INCREF(Py_None);
            tstate->exc_type = Py_None;
        }
        Py_INCREF(tstate->exc_type);
        Py_XINCREF(tstate->exc_value);
        Py_XINCREF(tstate->exc_traceback);
        frame->f_exc_type = tstate->exc_type;
        frame->f_exc_value = tstate->exc_value;
        frame->f_exc_traceback = tstate->exc_traceback;
    }
    /* Set new exception for this thread. */
    tmp_type = tstate->exc_type;
    tmp_value = tstate->exc_value;
    tmp_tb = tstate->exc_traceback;
    Py_INCREF(type);
    Py_XINCREF(value);
    Py_XINCREF(tb);
    tstate->exc_type = type;
    tstate->exc_value = value;
    tstate->exc_traceback = tb;
    Py_XDECREF(tmp_type);
    Py_XDECREF(tmp_value);
    Py_XDECREF(tmp_tb);
    /* For b/w compatibility */
    PySys_SetObject("exc_type", type);
    PySys_SetObject("exc_value", value);
    PySys_SetObject("exc_traceback", tb);
}

static void
reset_exc_info(PyThreadState *tstate)
{
    PyFrameObject *frame;
    PyObject *tmp_type, *tmp_value, *tmp_tb;

    /* It's a precondition that the thread state's frame caught an
     * exception -- verify in a debug build.
     */
    assert(tstate != NULL);
    frame = tstate->frame;
    assert(frame != NULL);
    assert(frame->f_exc_type != NULL);

    /* Copy the frame's exception info back to the thread state. */
    tmp_type = tstate->exc_type;
    tmp_value = tstate->exc_value;
    tmp_tb = tstate->exc_traceback;
    Py_INCREF(frame->f_exc_type);
    Py_XINCREF(frame->f_exc_value);
    Py_XINCREF(frame->f_exc_traceback);
    tstate->exc_type = frame->f_exc_type;
    tstate->exc_value = frame->f_exc_value;
    tstate->exc_traceback = frame->f_exc_traceback;
    Py_XDECREF(tmp_type);
    Py_XDECREF(tmp_value);
    Py_XDECREF(tmp_tb);

    /* For b/w compatibility */
    PySys_SetObject("exc_type", frame->f_exc_type);
    PySys_SetObject("exc_value", frame->f_exc_value);
    PySys_SetObject("exc_traceback", frame->f_exc_traceback);

    /* Clear the frame's exception info. */
    tmp_type = frame->f_exc_type;
    tmp_value = frame->f_exc_value;
    tmp_tb = frame->f_exc_traceback;
    frame->f_exc_type = NULL;
    frame->f_exc_value = NULL;
    frame->f_exc_traceback = NULL;
    Py_DECREF(tmp_type);
    Py_XDECREF(tmp_value);
    Py_XDECREF(tmp_tb);
}

/* Logic for the raise statement (too complicated for inlining).
   This *consumes* a reference count to each of its arguments. */
static enum why_code
do_raise(PyObject *type, PyObject *value, PyObject *tb)
{
    if (type == NULL) {
        /* Reraise */
        PyThreadState *tstate = PyThreadState_GET();
        type = tstate->exc_type == NULL ? Py_None : tstate->exc_type;
        value = tstate->exc_value;
        tb = tstate->exc_traceback;
        Py_XINCREF(type);
        Py_XINCREF(value);
        Py_XINCREF(tb);
    }

    /* We support the following forms of raise:
       raise <class>, <classinstance>
       raise <class>, <argument tuple>
       raise <class>, None
       raise <class>, <argument>
       raise <classinstance>, None
       raise <string>, <object>
       raise <string>, None

       An omitted second argument is the same as None.

       In addition, raise <tuple>, <anything> is the same as
       raising the tuple's first item (and it better have one!);
       this rule is applied recursively.

       Finally, an optional third argument can be supplied, which
       gives the traceback to be substituted (useful when
       re-raising an exception after examining it).  */

    /* First, check the traceback argument, replacing None with
       NULL. */
    if (tb == Py_None) {
        Py_DECREF(tb);
        tb = NULL;
    }
    else if (tb != NULL && !PyTraceBack_Check(tb)) {
        PyErr_SetString(PyExc_TypeError,
                   "raise: arg 3 must be a traceback or None");
        goto raise_error;
    }

    /* Next, replace a missing value with None */
    if (value == NULL) {
        value = Py_None;
        Py_INCREF(value);
    }

    /* Next, repeatedly, replace a tuple exception with its first item */
    while (PyTuple_Check(type) && PyTuple_Size(type) > 0) {
        PyObject *tmp = type;
        type = PyTuple_GET_ITEM(type, 0);
        Py_INCREF(type);
        Py_DECREF(tmp);
    }

    if (PyExceptionClass_Check(type)) {
        PyErr_NormalizeException(&type, &value, &tb);
        if (!PyExceptionInstance_Check(value)) {
            PyErr_Format(PyExc_TypeError,
                         "calling %s() should have returned an instance of "
                         "BaseException, not '%s'",
                         ((PyTypeObject *)type)->tp_name,
                         Py_TYPE(value)->tp_name);
            goto raise_error;
        }
    }
    else if (PyExceptionInstance_Check(type)) {
        /* Raising an instance.  The value should be a dummy. */
        if (value != Py_None) {
            PyErr_SetString(PyExc_TypeError,
              "instance exception may not have a separate value");
            goto raise_error;
        }
        else {
            /* Normalize to raise <class>, <instance> */
            Py_DECREF(value);
            value = type;
            type = PyExceptionInstance_Class(type);
            Py_INCREF(type);
        }
    }
    else {
        /* Not something you can raise.  You get an exception
           anyway, just not what you specified :-) */
        PyErr_Format(PyExc_TypeError,
                     "exceptions must be old-style classes or "
                     "derived from BaseException, not %s",
                     type->ob_type->tp_name);
        goto raise_error;
    }

    assert(PyExceptionClass_Check(type));
    if (Py_Py3kWarningFlag && PyClass_Check(type)) {
        if (PyErr_WarnEx(PyExc_DeprecationWarning,
                        "exceptions must derive from BaseException "
                        "in 3.x", 1) < 0)
            goto raise_error;
    }

    PyErr_Restore(type, value, tb);
    if (tb == NULL)
        return WHY_EXCEPTION;
    else
        return WHY_RERAISE;
 raise_error:
    Py_XDECREF(value);
    Py_XDECREF(type);
    Py_XDECREF(tb);
    return WHY_EXCEPTION;
}

/* Iterate v argcnt times and store the results on the stack (via decreasing
   sp).  Return 1 for success, 0 if error. */

static int
unpack_iterable(PyObject *v, int argcnt, PyObject **sp)
{
    int i = 0;
    PyObject *it;  /* iter(v) */
    PyObject *w;

    assert(v != NULL);

    it = PyObject_GetIter(v);
    if (it == NULL)
        goto Error;

    for (; i < argcnt; i++) {
        w = PyIter_Next(it);
        if (w == NULL) {
            /* Iterator done, via error or exhaustion. */
            if (!PyErr_Occurred()) {
                PyErr_Format(PyExc_ValueError,
                    "need more than %d value%s to unpack",
                    i, i == 1 ? "" : "s");
            }
            goto Error;
        }
        *--sp = w;
    }

    /* We better have exhausted the iterator now. */
    w = PyIter_Next(it);
    if (w == NULL) {
        if (PyErr_Occurred())
            goto Error;
        Py_DECREF(it);
        return 1;
    }
    Py_DECREF(w);
    PyErr_SetString(PyExc_ValueError, "too many values to unpack");
    /* fall through */
Error:
    for (; i > 0; i--, sp++)
        Py_DECREF(*sp);
    Py_XDECREF(it);
    return 0;
}


#ifdef LLTRACE
static int
prtrace(PyObject *v, char *str)
{
    printf("%s ", str);
    if (PyObject_Print(v, stdout, 0) != 0)
        PyErr_Clear(); /* Don't know what else to do */
    printf("\n");
    return 1;
}
#endif

static void
call_exc_trace(Py_tracefunc func, PyObject *self, PyFrameObject *f)
{
    PyObject *type, *value, *traceback, *arg;
    int err;
    PyErr_Fetch(&type, &value, &traceback);
    if (value == NULL) {
        value = Py_None;
        Py_INCREF(value);
    }
    arg = PyTuple_Pack(3, type, value, traceback);
    if (arg == NULL) {
        PyErr_Restore(type, value, traceback);
        return;
    }
    err = call_trace(func, self, f, PyTrace_EXCEPTION, arg);
    Py_DECREF(arg);
    if (err == 0)
        PyErr_Restore(type, value, traceback);
    else {
        Py_XDECREF(type);
        Py_XDECREF(value);
        Py_XDECREF(traceback);
    }
}

static int
call_trace_protected(Py_tracefunc func, PyObject *obj, PyFrameObject *frame,
                     int what, PyObject *arg)
{
    PyObject *type, *value, *traceback;
    int err;
    PyErr_Fetch(&type, &value, &traceback);
    err = call_trace(func, obj, frame, what, arg);
    if (err == 0)
    {
        PyErr_Restore(type, value, traceback);
        return 0;
    }
    else {
        Py_XDECREF(type);
        Py_XDECREF(value);
        Py_XDECREF(traceback);
        return -1;
    }
}

static int
call_trace(Py_tracefunc func, PyObject *obj, PyFrameObject *frame,
           int what, PyObject *arg)
{
    register PyThreadState *tstate = frame->f_tstate;
    int result;
    if (tstate->tracing)
        return 0;
    tstate->tracing++;
    tstate->use_tracing = 0;
    result = func(obj, frame, what, arg);
    tstate->use_tracing = ((tstate->c_tracefunc != NULL)
                           || (tstate->c_profilefunc != NULL));
    tstate->tracing--;
    return result;
}

PyObject *
_PyEval_CallTracing(PyObject *func, PyObject *args)
{
    PyFrameObject *frame = PyEval_GetFrame();
    PyThreadState *tstate = frame->f_tstate;
    int save_tracing = tstate->tracing;
    int save_use_tracing = tstate->use_tracing;
    PyObject *result;

    tstate->tracing = 0;
    tstate->use_tracing = ((tstate->c_tracefunc != NULL)
                           || (tstate->c_profilefunc != NULL));
    result = PyObject_Call(func, args, NULL);
    tstate->tracing = save_tracing;
    tstate->use_tracing = save_use_tracing;
    return result;
}

/* See Objects/lnotab_notes.txt for a description of how tracing works. */
static int
maybe_call_line_trace(Py_tracefunc func, PyObject *obj,
                      PyFrameObject *frame, int *instr_lb, int *instr_ub,
                      int *instr_prev)
{
    int result = 0;
    int line = frame->f_lineno;

    /* If the last instruction executed isn't in the current
       instruction window, reset the window.
    */
    if (frame->f_lasti < *instr_lb || frame->f_lasti >= *instr_ub) {
        PyAddrPair bounds;
        line = _PyCode_CheckLineNumber(frame->f_code, frame->f_lasti,
                                       &bounds);
        *instr_lb = bounds.ap_lower;
        *instr_ub = bounds.ap_upper;
    }
    /* If the last instruction falls at the start of a line or if
       it represents a jump backwards, update the frame's line
       number and call the trace function. */
    if (frame->f_lasti == *instr_lb || frame->f_lasti < *instr_prev) {
        frame->f_lineno = line;
        result = call_trace(func, obj, frame, PyTrace_LINE, Py_None);
    }
    *instr_prev = frame->f_lasti;
    return result;
}

void
PyEval_SetProfile(Py_tracefunc func, PyObject *arg)
{
    PyThreadState *tstate = PyThreadState_GET();
    PyObject *temp = tstate->c_profileobj;
    Py_XINCREF(arg);
    tstate->c_profilefunc = NULL;
    tstate->c_profileobj = NULL;
    /* Must make sure that tracing is not ignored if 'temp' is freed */
    tstate->use_tracing = tstate->c_tracefunc != NULL;
    Py_XDECREF(temp);
    tstate->c_profilefunc = func;
    tstate->c_profileobj = arg;
    /* Flag that tracing or profiling is turned on */
    tstate->use_tracing = (func != NULL) || (tstate->c_tracefunc != NULL);
}

void
PyEval_SetTrace(Py_tracefunc func, PyObject *arg)
{
    PyThreadState *tstate = PyThreadState_GET();
    PyObject *temp = tstate->c_traceobj;
    _Py_TracingPossible += (func != NULL) - (tstate->c_tracefunc != NULL);
    Py_XINCREF(arg);
    tstate->c_tracefunc = NULL;
    tstate->c_traceobj = NULL;
    /* Must make sure that profiling is not ignored if 'temp' is freed */
    tstate->use_tracing = tstate->c_profilefunc != NULL;
    Py_XDECREF(temp);
    tstate->c_tracefunc = func;
    tstate->c_traceobj = arg;
    /* Flag that tracing or profiling is turned on */
    tstate->use_tracing = ((func != NULL)
                           || (tstate->c_profilefunc != NULL));
}

PyObject *
PyEval_GetBuiltins(void)
{
    PyFrameObject *current_frame = PyEval_GetFrame();
    if (current_frame == NULL)
        return PyThreadState_GET()->interp->builtins;
    else
        return current_frame->f_builtins;
}

PyObject *
PyEval_GetLocals(void)
{
    PyFrameObject *current_frame = PyEval_GetFrame();
    if (current_frame == NULL)
        return NULL;
    PyFrame_FastToLocals(current_frame);
    return current_frame->f_locals;
}

PyObject *
PyEval_GetGlobals(void)
{
    PyFrameObject *current_frame = PyEval_GetFrame();
    if (current_frame == NULL)
        return NULL;
    else
        return current_frame->f_globals;
}

PyFrameObject *
PyEval_GetFrame(void)
{
    PyThreadState *tstate = PyThreadState_GET();
    return _PyThreadState_GetFrame(tstate);
}

int
PyEval_GetRestricted(void)
{
    PyFrameObject *current_frame = PyEval_GetFrame();
    return current_frame == NULL ? 0 : PyFrame_IsRestricted(current_frame);
}

int
PyEval_MergeCompilerFlags(PyCompilerFlags *cf)
{
    PyFrameObject *current_frame = PyEval_GetFrame();
    int result = cf->cf_flags != 0;

    if (current_frame != NULL) {
        const int codeflags = current_frame->f_code->co_flags;
        const int compilerflags = codeflags & PyCF_MASK;
        if (compilerflags) {
            result = 1;
            cf->cf_flags |= compilerflags;
        }
#if 0 /* future keyword */
        if (codeflags & CO_GENERATOR_ALLOWED) {
            result = 1;
            cf->cf_flags |= CO_GENERATOR_ALLOWED;
        }
#endif
    }
    return result;
}

int
Py_FlushLine(void)
{
    PyObject *f = PySys_GetObject("stdout");
    if (f == NULL)
        return 0;
    if (!PyFile_SoftSpace(f, 0))
        return 0;
    return PyFile_WriteString("\n", f);
}


/* External interface to call any callable object.
   The arg must be a tuple or NULL.  The kw must be a dict or NULL. */

PyObject *
PyEval_CallObjectWithKeywords(PyObject *func, PyObject *arg, PyObject *kw)
{
    PyObject *result;

    if (arg == NULL) {
        arg = PyTuple_New(0);
        if (arg == NULL)
            return NULL;
    }
    else if (!PyTuple_Check(arg)) {
        PyErr_SetString(PyExc_TypeError,
                        "argument list must be a tuple");
        return NULL;
    }
    else
        Py_INCREF(arg);

    if (kw != NULL && !PyDict_Check(kw)) {
        PyErr_SetString(PyExc_TypeError,
                        "keyword list must be a dictionary");
        Py_DECREF(arg);
        return NULL;
    }

    result = PyObject_Call(func, arg, kw);
    Py_DECREF(arg);
    return result;
}

const char *
PyEval_GetFuncName(PyObject *func)
{
    if (PyMethod_Check(func))
        return PyEval_GetFuncName(PyMethod_GET_FUNCTION(func));
    else if (PyFunction_Check(func))
        return PyString_AsString(((PyFunctionObject*)func)->func_name);
    else if (PyCFunction_Check(func))
        return ((PyCFunctionObject*)func)->m_ml->ml_name;
    else if (PyClass_Check(func))
        return PyString_AsString(((PyClassObject*)func)->cl_name);
    else if (PyInstance_Check(func)) {
        return PyString_AsString(
            ((PyInstanceObject*)func)->in_class->cl_name);
    } else {
        return func->ob_type->tp_name;
    }
}

const char *
PyEval_GetFuncDesc(PyObject *func)
{
    if (PyMethod_Check(func))
        return "()";
    else if (PyFunction_Check(func))
        return "()";
    else if (PyCFunction_Check(func))
        return "()";
    else if (PyClass_Check(func))
        return " constructor";
    else if (PyInstance_Check(func)) {
        return " instance";
    } else {
        return " object";
    }
}

static void
err_args(PyObject *func, int flags, int nargs)
{
    if (flags & METH_NOARGS)
        PyErr_Format(PyExc_TypeError,
                     "%.200s() takes no arguments (%d given)",
                     ((PyCFunctionObject *)func)->m_ml->ml_name,
                     nargs);
    else
        PyErr_Format(PyExc_TypeError,
                     "%.200s() takes exactly one argument (%d given)",
                     ((PyCFunctionObject *)func)->m_ml->ml_name,
                     nargs);
}

#define C_TRACE(x, call) \
if (tstate->use_tracing && tstate->c_profilefunc) { \
    if (call_trace(tstate->c_profilefunc, \
        tstate->c_profileobj, \
        tstate->frame, PyTrace_C_CALL, \
        func)) { \
        x = NULL; \
    } \
    else { \
        x = call; \
        if (tstate->c_profilefunc != NULL) { \
            if (x == NULL) { \
                call_trace_protected(tstate->c_profilefunc, \
                    tstate->c_profileobj, \
                    tstate->frame, PyTrace_C_EXCEPTION, \
                    func); \
                /* XXX should pass (type, value, tb) */ \
            } else { \
                if (call_trace(tstate->c_profilefunc, \
                    tstate->c_profileobj, \
                    tstate->frame, PyTrace_C_RETURN, \
                    func)) { \
                    Py_DECREF(x); \
                    x = NULL; \
                } \
            } \
        } \
    } \
} else { \
    x = call; \
    }

static PyObject *
call_function(PyObject ***pp_stack, int oparg
#ifdef WITH_TSC
                , uint64* pintr0, uint64* pintr1
#endif
                )
{
    int na = oparg & 0xff;
    int nk = (oparg>>8) & 0xff;
    int n = na + 2 * nk;
    PyObject **pfunc = (*pp_stack) - n - 1;
    PyObject *func = *pfunc;
    PyObject *x, *w;

    /* Always dispatch PyCFunction first, because these are
       presumed to be the most frequent callable object.
    */
    if (PyCFunction_Check(func) && nk == 0) {
        int flags = PyCFunction_GET_FLAGS(func);
        PyThreadState *tstate = PyThreadState_GET();

        PCALL(PCALL_CFUNCTION);
        if (flags & (METH_NOARGS | METH_O)) {
            PyCFunction meth = PyCFunction_GET_FUNCTION(func);
            PyObject *self = PyCFunction_GET_SELF(func);
            if (flags & METH_NOARGS && na == 0) {
                C_TRACE(x, (*meth)(self,NULL));
            }
            else if (flags & METH_O && na == 1) {
                PyObject *arg = EXT_POP(*pp_stack);
                C_TRACE(x, (*meth)(self,arg));
                Py_DECREF(arg);
            }
            else {
                err_args(func, flags, na);
                x = NULL;
            }
        }
        else {
            PyObject *callargs;
            callargs = load_args(pp_stack, na);
            READ_TIMESTAMP(*pintr0);
            C_TRACE(x, PyCFunction_Call(func,callargs,NULL));
            READ_TIMESTAMP(*pintr1);
            Py_XDECREF(callargs);
        }
    } else {
        if (PyMethod_Check(func) && PyMethod_GET_SELF(func) != NULL) {
            /* optimize access to bound methods */
            PyObject *self = PyMethod_GET_SELF(func);
            PCALL(PCALL_METHOD);
            PCALL(PCALL_BOUND_METHOD);
            Py_INCREF(self);
            func = PyMethod_GET_FUNCTION(func);
            Py_INCREF(func);
            Py_DECREF(*pfunc);
            *pfunc = self;
            na++;
            n++;
        } else
            Py_INCREF(func);
        READ_TIMESTAMP(*pintr0);
        if (PyFunction_Check(func))
            x = fast_function(func, pp_stack, n, na, nk);
        else
            x = do_call(func, pp_stack, na, nk);
        READ_TIMESTAMP(*pintr1);
        Py_DECREF(func);
    }

    /* Clear the stack of the function object.  Also removes
       the arguments in case they weren't consumed already
       (fast_function() and err_args() leave them on the stack).
     */
    while ((*pp_stack) > pfunc) {
        w = EXT_POP(*pp_stack);
        Py_DECREF(w);
        PCALL(PCALL_POP);
    }
    return x;
}

/* The fast_function() function optimize calls for which no argument
   tuple is necessary; the objects are passed directly from the stack.
   For the simplest case -- a function that takes only positional
   arguments and is called with only positional arguments -- it
   inlines the most primitive frame setup code from
   PyEval_EvalCodeEx(), which vastly reduces the checks that must be
   done before evaluating the frame.
*/

static PyObject *
fast_function(PyObject *func, PyObject ***pp_stack, int n, int na, int nk)
{
    PyCodeObject *co = (PyCodeObject *)PyFunction_GET_CODE(func);
    PyObject *globals = PyFunction_GET_GLOBALS(func);
    PyObject *argdefs = PyFunction_GET_DEFAULTS(func);
    PyObject **d = NULL;
    int nd = 0;

    PCALL(PCALL_FUNCTION);
    PCALL(PCALL_FAST_FUNCTION);
    if (argdefs == NULL && co->co_argcount == n && nk==0 &&
        co->co_flags == (CO_OPTIMIZED | CO_NEWLOCALS | CO_NOFREE)) {
        PyFrameObject *f;
        PyObject *retval = NULL;
        PyThreadState *tstate = PyThreadState_GET();
        PyObject **fastlocals, **stack;
        int i;

        PCALL(PCALL_FASTER_FUNCTION);
        assert(globals != NULL);
        /* XXX Perhaps we should create a specialized
           PyFrame_New() that doesn't take locals, but does
           take builtins without sanity checking them.
        */
        assert(tstate != NULL);
        f = PyFrame_New(tstate, co, globals, NULL);
        if (f == NULL)
            return NULL;

        fastlocals = f->f_localsplus;
        stack = (*pp_stack) - n;

        for (i = 0; i < n; i++) {
            Py_INCREF(*stack);
            fastlocals[i] = *stack++;
        }
        retval = PyEval_EvalFrameEx(f,0);
        ++tstate->recursion_depth;
        Py_DECREF(f);
        --tstate->recursion_depth;
        return retval;
    }
    if (argdefs != NULL) {
        d = &PyTuple_GET_ITEM(argdefs, 0);
        nd = Py_SIZE(argdefs);
    }
    return PyEval_EvalCodeEx(co, globals,
                             (PyObject *)NULL, (*pp_stack)-n, na,
                             (*pp_stack)-2*nk, nk, d, nd,
                             PyFunction_GET_CLOSURE(func));
}

static PyObject *
update_keyword_args(PyObject *orig_kwdict, int nk, PyObject ***pp_stack,
                    PyObject *func)
{
    PyObject *kwdict = NULL;
    if (orig_kwdict == NULL)
        kwdict = PyDict_New();
    else {
        kwdict = PyDict_Copy(orig_kwdict);
        Py_DECREF(orig_kwdict);
    }
    if (kwdict == NULL)
        return NULL;
    while (--nk >= 0) {
        int err;
        PyObject *value = EXT_POP(*pp_stack);
        PyObject *key = EXT_POP(*pp_stack);
        if (PyDict_GetItem(kwdict, key) != NULL) {
            PyErr_Format(PyExc_TypeError,
                         "%.200s%s got multiple values "
                         "for keyword argument '%.200s'",
                         PyEval_GetFuncName(func),
                         PyEval_GetFuncDesc(func),
                         PyString_AsString(key));
            Py_DECREF(key);
            Py_DECREF(value);
            Py_DECREF(kwdict);
            return NULL;
        }
        err = PyDict_SetItem(kwdict, key, value);
        Py_DECREF(key);
        Py_DECREF(value);
        if (err) {
            Py_DECREF(kwdict);
            return NULL;
        }
    }
    return kwdict;
}

static PyObject *
update_star_args(int nstack, int nstar, PyObject *stararg,
                 PyObject ***pp_stack)
{
    PyObject *callargs, *w;

    callargs = PyTuple_New(nstack + nstar);
    if (callargs == NULL) {
        return NULL;
    }
    if (nstar) {
        int i;
        for (i = 0; i < nstar; i++) {
            PyObject *a = PyTuple_GET_ITEM(stararg, i);
            Py_INCREF(a);
            PyTuple_SET_ITEM(callargs, nstack + i, a);
        }
    }
    while (--nstack >= 0) {
        w = EXT_POP(*pp_stack);
        PyTuple_SET_ITEM(callargs, nstack, w);
    }
    return callargs;
}

static PyObject *
load_args(PyObject ***pp_stack, int na)
{
    PyObject *args = PyTuple_New(na);
    PyObject *w;

    if (args == NULL)
        return NULL;
    while (--na >= 0) {
        w = EXT_POP(*pp_stack);
        PyTuple_SET_ITEM(args, na, w);
    }
    return args;
}

static PyObject *
do_call(PyObject *func, PyObject ***pp_stack, int na, int nk)
{
    PyObject *callargs = NULL;
    PyObject *kwdict = NULL;
    PyObject *result = NULL;

    if (nk > 0) {
        kwdict = update_keyword_args(NULL, nk, pp_stack, func);
        if (kwdict == NULL)
            goto call_fail;
    }
    callargs = load_args(pp_stack, na);
    if (callargs == NULL)
        goto call_fail;
#ifdef CALL_PROFILE
    /* At this point, we have to look at the type of func to
       update the call stats properly.  Do it here so as to avoid
       exposing the call stats machinery outside ceval.c
    */
    if (PyFunction_Check(func))
        PCALL(PCALL_FUNCTION);
    else if (PyMethod_Check(func))
        PCALL(PCALL_METHOD);
    else if (PyType_Check(func))
        PCALL(PCALL_TYPE);
    else if (PyCFunction_Check(func))
        PCALL(PCALL_CFUNCTION);
    else
        PCALL(PCALL_OTHER);
#endif
    if (PyCFunction_Check(func)) {
        PyThreadState *tstate = PyThreadState_GET();
        C_TRACE(result, PyCFunction_Call(func, callargs, kwdict));
    }
    else
        result = PyObject_Call(func, callargs, kwdict);
 call_fail:
    Py_XDECREF(callargs);
    Py_XDECREF(kwdict);
    return result;
}

static PyObject *
ext_do_call(PyObject *func, PyObject ***pp_stack, int flags, int na, int nk)
{
    int nstar = 0;
    PyObject *callargs = NULL;
    PyObject *stararg = NULL;
    PyObject *kwdict = NULL;
    PyObject *result = NULL;

    if (flags & CALL_FLAG_KW) {
        kwdict = EXT_POP(*pp_stack);
        if (!PyDict_Check(kwdict)) {
            PyObject *d;
            d = PyDict_New();
            if (d == NULL)
                goto ext_call_fail;
            if (PyDict_Update(d, kwdict) != 0) {
                Py_DECREF(d);
                /* PyDict_Update raises attribute
                 * error (percolated from an attempt
                 * to get 'keys' attribute) instead of
                 * a type error if its second argument
                 * is not a mapping.
                 */
                if (PyErr_ExceptionMatches(PyExc_AttributeError)) {
                    PyErr_Format(PyExc_TypeError,
                                 "%.200s%.200s argument after ** "
                                 "must be a mapping, not %.200s",
                                 PyEval_GetFuncName(func),
                                 PyEval_GetFuncDesc(func),
                                 kwdict->ob_type->tp_name);
                }
                goto ext_call_fail;
            }
            Py_DECREF(kwdict);
            kwdict = d;
        }
    }
    if (flags & CALL_FLAG_VAR) {
        stararg = EXT_POP(*pp_stack);
        if (!PyTuple_Check(stararg)) {
            PyObject *t = NULL;
            t = PySequence_Tuple(stararg);
            if (t == NULL) {
                if (PyErr_ExceptionMatches(PyExc_TypeError)) {
                    PyErr_Format(PyExc_TypeError,
                                 "%.200s%.200s argument after * "
                                 "must be a sequence, not %200s",
                                 PyEval_GetFuncName(func),
                                 PyEval_GetFuncDesc(func),
                                 stararg->ob_type->tp_name);
                }
                goto ext_call_fail;
            }
            Py_DECREF(stararg);
            stararg = t;
        }
        nstar = PyTuple_GET_SIZE(stararg);
    }
    if (nk > 0) {
        kwdict = update_keyword_args(kwdict, nk, pp_stack, func);
        if (kwdict == NULL)
            goto ext_call_fail;
    }
    callargs = update_star_args(na, nstar, stararg, pp_stack);
    if (callargs == NULL)
        goto ext_call_fail;
#ifdef CALL_PROFILE
    /* At this point, we have to look at the type of func to
       update the call stats properly.  Do it here so as to avoid
       exposing the call stats machinery outside ceval.c
    */
    if (PyFunction_Check(func))
        PCALL(PCALL_FUNCTION);
    else if (PyMethod_Check(func))
        PCALL(PCALL_METHOD);
    else if (PyType_Check(func))
        PCALL(PCALL_TYPE);
    else if (PyCFunction_Check(func))
        PCALL(PCALL_CFUNCTION);
    else
        PCALL(PCALL_OTHER);
#endif
    if (PyCFunction_Check(func)) {
        PyThreadState *tstate = PyThreadState_GET();
        C_TRACE(result, PyCFunction_Call(func, callargs, kwdict));
    }
    else
        result = PyObject_Call(func, callargs, kwdict);
ext_call_fail:
    Py_XDECREF(callargs);
    Py_XDECREF(kwdict);
    Py_XDECREF(stararg);
    return result;
}

/* Extract a slice index from a PyInt or PyLong or an object with the
   nb_index slot defined, and store in *pi.
   Silently reduce values larger than PY_SSIZE_T_MAX to PY_SSIZE_T_MAX,
   and silently boost values less than -PY_SSIZE_T_MAX-1 to -PY_SSIZE_T_MAX-1.
   Return 0 on error, 1 on success.
*/
/* Note:  If v is NULL, return success without storing into *pi.  This
   is because_PyEval_SliceIndex() is called by apply_slice(), which can be
   called by the SLICE opcode with v and/or w equal to NULL.
*/
int
_PyEval_SliceIndex(PyObject *v, Py_ssize_t *pi)
{
    if (v != NULL) {
        Py_ssize_t x;
        if (PyInt_Check(v)) {
            /* XXX(nnorwitz): I think PyInt_AS_LONG is correct,
               however, it looks like it should be AsSsize_t.
               There should be a comment here explaining why.
            */
            x = PyInt_AS_LONG(v);
        }
        else if (PyIndex_Check(v)) {
            x = PyNumber_AsSsize_t(v, NULL);
            if (x == -1 && PyErr_Occurred())
                return 0;
        }
        else {
            PyErr_SetString(PyExc_TypeError,
                            "slice indices must be integers or "
                            "None or have an __index__ method");
            return 0;
        }
        *pi = x;
    }
    return 1;
}

#undef ISINDEX
#define ISINDEX(x) ((x) == NULL || \
                    PyInt_Check(x) || PyLong_Check(x) || PyIndex_Check(x))

static PyObject *
apply_slice(PyObject *u, PyObject *v, PyObject *w) /* return u[v:w] */
{
    PyTypeObject *tp = u->ob_type;
    PySequenceMethods *sq = tp->tp_as_sequence;

    if (sq && sq->sq_slice && ISINDEX(v) && ISINDEX(w)) {
        Py_ssize_t ilow = 0, ihigh = PY_SSIZE_T_MAX;
        if (!_PyEval_SliceIndex(v, &ilow))
            return NULL;
        if (!_PyEval_SliceIndex(w, &ihigh))
            return NULL;
        return PySequence_GetSlice(u, ilow, ihigh);
    }
    else {
        PyObject *slice = PySlice_New(v, w, NULL);
        if (slice != NULL) {
            PyObject *res = PyObject_GetItem(u, slice);
            Py_DECREF(slice);
            return res;
        }
        else
            return NULL;
    }
}

static int
assign_slice(PyObject *u, PyObject *v, PyObject *w, PyObject *x)
    /* u[v:w] = x */
{
    PyTypeObject *tp = u->ob_type;
    PySequenceMethods *sq = tp->tp_as_sequence;

    if (sq && sq->sq_ass_slice && ISINDEX(v) && ISINDEX(w)) {
        Py_ssize_t ilow = 0, ihigh = PY_SSIZE_T_MAX;
        if (!_PyEval_SliceIndex(v, &ilow))
            return -1;
        if (!_PyEval_SliceIndex(w, &ihigh))
            return -1;
        if (x == NULL)
            return PySequence_DelSlice(u, ilow, ihigh);
        else
            return PySequence_SetSlice(u, ilow, ihigh, x);
    }
    else {
        PyObject *slice = PySlice_New(v, w, NULL);
        if (slice != NULL) {
            int res;
            if (x != NULL)
                res = PyObject_SetItem(u, slice, x);
            else
                res = PyObject_DelItem(u, slice);
            Py_DECREF(slice);
            return res;
        }
        else
            return -1;
    }
}

#define Py3kExceptionClass_Check(x)     \
    (PyType_Check((x)) &&               \
     PyType_FastSubclass((PyTypeObject*)(x), Py_TPFLAGS_BASE_EXC_SUBCLASS))

#define CANNOT_CATCH_MSG "catching classes that don't inherit from " \
                         "BaseException is not allowed in 3.x"

static PyObject *
cmp_outcome(int op, register PyObject *v, register PyObject *w)
{
    int res = 0;
    switch (op) {
    case PyCmp_IS:
        res = (v == w);
        break;
    case PyCmp_IS_NOT:
        res = (v != w);
        break;
    case PyCmp_IN:
        res = PySequence_Contains(w, v);
        if (res < 0)
            return NULL;
        break;
    case PyCmp_NOT_IN:
        res = PySequence_Contains(w, v);
        if (res < 0)
            return NULL;
        res = !res;
        break;
    case PyCmp_EXC_MATCH:
        if (PyTuple_Check(w)) {
            Py_ssize_t i, length;
            length = PyTuple_Size(w);
            for (i = 0; i < length; i += 1) {
                PyObject *exc = PyTuple_GET_ITEM(w, i);
                if (PyString_Check(exc)) {
                    int ret_val;
                    ret_val = PyErr_WarnEx(
                        PyExc_DeprecationWarning,
                        "catching of string "
                        "exceptions is deprecated", 1);
                    if (ret_val < 0)
                        return NULL;
                }
                else if (Py_Py3kWarningFlag  &&
                         !PyTuple_Check(exc) &&
                         !Py3kExceptionClass_Check(exc))
                {
                    int ret_val;
                    ret_val = PyErr_WarnEx(
                        PyExc_DeprecationWarning,
                        CANNOT_CATCH_MSG, 1);
                    if (ret_val < 0)
                        return NULL;
                }
            }
        }
        else {
            if (PyString_Check(w)) {
                int ret_val;
                ret_val = PyErr_WarnEx(
                                PyExc_DeprecationWarning,
                                "catching of string "
                                "exceptions is deprecated", 1);
                if (ret_val < 0)
                    return NULL;
            }
            else if (Py_Py3kWarningFlag  &&
                     !PyTuple_Check(w) &&
                     !Py3kExceptionClass_Check(w))
            {
                int ret_val;
                ret_val = PyErr_WarnEx(
                    PyExc_DeprecationWarning,
                    CANNOT_CATCH_MSG, 1);
                if (ret_val < 0)
                    return NULL;
            }
        }
        res = PyErr_GivenExceptionMatches(v, w);
        break;
    default:
        return PyObject_RichCompare(v, w, op);
    }
    v = res ? Py_True : Py_False;
    Py_INCREF(v);
    return v;
}

static PyObject *
import_from(PyObject *v, PyObject *name)
{
    PyObject *x;

    x = PyObject_GetAttr(v, name);
    if (x == NULL && PyErr_ExceptionMatches(PyExc_AttributeError)) {
        PyErr_Format(PyExc_ImportError,
                     "cannot import name %.230s",
                     PyString_AsString(name));
    }
    return x;
}

static int
import_all_from(PyObject *locals, PyObject *v)
{
    PyObject *all = PyObject_GetAttrString(v, "__all__");
    PyObject *dict, *name, *value;
    int skip_leading_underscores = 0;
    int pos, err;

    if (all == NULL) {
        if (!PyErr_ExceptionMatches(PyExc_AttributeError))
            return -1; /* Unexpected error */
        PyErr_Clear();
        dict = PyObject_GetAttrString(v, "__dict__");
        if (dict == NULL) {
            if (!PyErr_ExceptionMatches(PyExc_AttributeError))
                return -1;
            PyErr_SetString(PyExc_ImportError,
            "from-import-* object has no __dict__ and no __all__");
            return -1;
        }
        all = PyMapping_Keys(dict);
        Py_DECREF(dict);
        if (all == NULL)
            return -1;
        skip_leading_underscores = 1;
    }

    for (pos = 0, err = 0; ; pos++) {
        name = PySequence_GetItem(all, pos);
        if (name == NULL) {
            if (!PyErr_ExceptionMatches(PyExc_IndexError))
                err = -1;
            else
                PyErr_Clear();
            break;
        }
        if (skip_leading_underscores &&
            PyString_Check(name) &&
            PyString_AS_STRING(name)[0] == '_')
        {
            Py_DECREF(name);
            continue;
        }
        value = PyObject_GetAttr(v, name);
        if (value == NULL)
            err = -1;
        else if (PyDict_CheckExact(locals))
            err = PyDict_SetItem(locals, name, value);
        else
            err = PyObject_SetItem(locals, name, value);
        Py_DECREF(name);
        Py_XDECREF(value);
        if (err != 0)
            break;
    }
    Py_DECREF(all);
    return err;
}

static PyObject *
build_class(PyObject *methods, PyObject *bases, PyObject *name)
{
    PyObject *metaclass = NULL, *result, *base;

    if (PyDict_Check(methods))
        metaclass = PyDict_GetItemString(methods, "__metaclass__");
    if (metaclass != NULL)
        Py_INCREF(metaclass);
    else if (PyTuple_Check(bases) && PyTuple_GET_SIZE(bases) > 0) {
        base = PyTuple_GET_ITEM(bases, 0);
        metaclass = PyObject_GetAttrString(base, "__class__");
        if (metaclass == NULL) {
            PyErr_Clear();
            metaclass = (PyObject *)base->ob_type;
            Py_INCREF(metaclass);
        }
    }
    else {
        PyObject *g = PyEval_GetGlobals();
        if (g != NULL && PyDict_Check(g))
            metaclass = PyDict_GetItemString(g, "__metaclass__");
        if (metaclass == NULL)
            metaclass = (PyObject *) &PyClass_Type;
        Py_INCREF(metaclass);
    }
    result = PyObject_CallFunctionObjArgs(metaclass, name, bases, methods,
                                          NULL);
    Py_DECREF(metaclass);
    if (result == NULL && PyErr_ExceptionMatches(PyExc_TypeError)) {
        /* A type error here likely means that the user passed
           in a base that was not a class (such the random module
           instead of the random.random type).  Help them out with
           by augmenting the error message with more information.*/

        PyObject *ptype, *pvalue, *ptraceback;

        PyErr_Fetch(&ptype, &pvalue, &ptraceback);
        if (PyString_Check(pvalue)) {
            PyObject *newmsg;
            newmsg = PyString_FromFormat(
                "Error when calling the metaclass bases\n"
                "    %s",
                PyString_AS_STRING(pvalue));
            if (newmsg != NULL) {
                Py_DECREF(pvalue);
                pvalue = newmsg;
            }
        }
        PyErr_Restore(ptype, pvalue, ptraceback);
    }
    return result;
}

static int
exec_statement(PyFrameObject *f, PyObject *prog, PyObject *globals,
               PyObject *locals)
{
    int n;
    PyObject *v;
    int plain = 0;

    if (PyTuple_Check(prog) && globals == Py_None && locals == Py_None &&
        ((n = PyTuple_Size(prog)) == 2 || n == 3)) {
        /* Backward compatibility hack */
        globals = PyTuple_GetItem(prog, 1);
        if (n == 3)
            locals = PyTuple_GetItem(prog, 2);
        prog = PyTuple_GetItem(prog, 0);
    }
    if (globals == Py_None) {
        globals = PyEval_GetGlobals();
        if (locals == Py_None) {
            locals = PyEval_GetLocals();
            plain = 1;
        }
        if (!globals || !locals) {
            PyErr_SetString(PyExc_SystemError,
                            "globals and locals cannot be NULL");
            return -1;
        }
    }
    else if (locals == Py_None)
        locals = globals;
    if (!PyString_Check(prog) &&
#ifdef Py_USING_UNICODE
        !PyUnicode_Check(prog) &&
#endif
        !PyCode_Check(prog) &&
        !PyFile_Check(prog)) {
        PyErr_SetString(PyExc_TypeError,
            "exec: arg 1 must be a string, file, or code object");
        return -1;
    }
    if (!PyDict_Check(globals)) {
        PyErr_SetString(PyExc_TypeError,
            "exec: arg 2 must be a dictionary or None");
        return -1;
    }
    if (!PyMapping_Check(locals)) {
        PyErr_SetString(PyExc_TypeError,
            "exec: arg 3 must be a mapping or None");
        return -1;
    }
    if (PyDict_GetItemString(globals, "__builtins__") == NULL)
        PyDict_SetItemString(globals, "__builtins__", f->f_builtins);
    if (PyCode_Check(prog)) {
        if (PyCode_GetNumFree((PyCodeObject *)prog) > 0) {
            PyErr_SetString(PyExc_TypeError,
        "code object passed to exec may not contain free variables");
            return -1;
        }
        v = PyEval_EvalCode((PyCodeObject *) prog, globals, locals);
    }
    else if (PyFile_Check(prog)) {
        FILE *fp = PyFile_AsFile(prog);
        char *name = PyString_AsString(PyFile_Name(prog));
        PyCompilerFlags cf;
        if (name == NULL)
            return -1;
        cf.cf_flags = 0;
        if (PyEval_MergeCompilerFlags(&cf))
            v = PyRun_FileFlags(fp, name, Py_file_input, globals,
                                locals, &cf);
        else
            v = PyRun_File(fp, name, Py_file_input, globals,
                           locals);
    }
    else {
        PyObject *tmp = NULL;
        char *str;
        PyCompilerFlags cf;
        cf.cf_flags = 0;
#ifdef Py_USING_UNICODE
        if (PyUnicode_Check(prog)) {
            tmp = PyUnicode_AsUTF8String(prog);
            if (tmp == NULL)
                return -1;
            prog = tmp;
            cf.cf_flags |= PyCF_SOURCE_IS_UTF8;
        }
#endif
        if (PyString_AsStringAndSize(prog, &str, NULL))
            return -1;
        if (PyEval_MergeCompilerFlags(&cf))
            v = PyRun_StringFlags(str, Py_file_input, globals,
                                  locals, &cf);
        else
            v = PyRun_String(str, Py_file_input, globals, locals);
        Py_XDECREF(tmp);
    }
    if (plain)
        PyFrame_LocalsToFast(f, 0);
    if (v == NULL)
        return -1;
    Py_DECREF(v);
    return 0;
}

static void
format_exc_check_arg(PyObject *exc, char *format_str, PyObject *obj)
{
    char *obj_str;

    if (!obj)
        return;

    obj_str = PyString_AsString(obj);
    if (!obj_str)
        return;

    PyErr_Format(exc, format_str, obj_str);
}

static PyObject *
string_concatenate(PyObject *v, PyObject *w,
                   PyFrameObject *f, unsigned char *next_instr)
{
    /* This function implements 'variable += expr' when both arguments
       are strings. */
    Py_ssize_t v_len = PyString_GET_SIZE(v);
    Py_ssize_t w_len = PyString_GET_SIZE(w);
    Py_ssize_t new_len = v_len + w_len;
    if (new_len < 0) {
        PyErr_SetString(PyExc_OverflowError,
                        "strings are too large to concat");
        return NULL;
    }

    if (v->ob_refcnt == 2) {
        /* In the common case, there are 2 references to the value
         * stored in 'variable' when the += is performed: one on the
         * value stack (in 'v') and one still stored in the
         * 'variable'.  We try to delete the variable now to reduce
         * the refcnt to 1.
         */
        switch (*next_instr) {
        case STORE_FAST:
        {
            int oparg = PEEKARG();
            PyObject **fastlocals = f->f_localsplus;
            if (GETLOCAL(oparg) == v)
                SETLOCAL(oparg, NULL);
            break;
        }
        case STORE_DEREF:
        {
            PyObject **freevars = (f->f_localsplus +
                                   f->f_code->co_nlocals);
            PyObject *c = freevars[PEEKARG()];
            if (PyCell_GET(c) == v)
                PyCell_Set(c, NULL);
            break;
        }
        case STORE_NAME:
        {
            PyObject *names = f->f_code->co_names;
            PyObject *name = GETITEM(names, PEEKARG());
            PyObject *locals = f->f_locals;
            if (PyDict_CheckExact(locals) &&
                PyDict_GetItem(locals, name) == v) {
                if (PyDict_DelItem(locals, name) != 0) {
                    PyErr_Clear();
                }
            }
            break;
        }
        }
    }

    if (v->ob_refcnt == 1 && !PyString_CHECK_INTERNED(v)) {
        /* Now we own the last reference to 'v', so we can resize it
         * in-place.
         */
        if (_PyString_Resize(&v, new_len) != 0) {
            /* XXX if _PyString_Resize() fails, 'v' has been
             * deallocated so it cannot be put back into
             * 'variable'.  The MemoryError is raised when there
             * is no value in 'variable', which might (very
             * remotely) be a cause of incompatibilities.
             */
            return NULL;
        }
        /* copy 'w' into the newly allocated area of 'v' */
        memcpy(PyString_AS_STRING(v) + v_len,
               PyString_AS_STRING(w), w_len);
        return v;
    }
    else {
        /* When in-place resizing is not an option. */
        PyString_Concat(&v, w);
        return v;
    }
}

#ifdef DYNAMIC_EXECUTION_PROFILE

static PyObject *
getarray(long a[256])
{
    int i;
    PyObject *l = PyList_New(256);
    if (l == NULL) return NULL;
    for (i = 0; i < 256; i++) {
        PyObject *x = PyInt_FromLong(a[i]);
        if (x == NULL) {
            Py_DECREF(l);
            return NULL;
        }
        PyList_SetItem(l, i, x);
    }
    for (i = 0; i < 256; i++)
        a[i] = 0;
    return l;
}

PyObject *
_Py_GetDXProfile(PyObject *self, PyObject *args)
{
#ifndef DXPAIRS
    return getarray(dxp);
#else
    int i;
    PyObject *l = PyList_New(257);
    if (l == NULL) return NULL;
    for (i = 0; i < 257; i++) {
        PyObject *x = getarray(dxpairs[i]);
        if (x == NULL) {
            Py_DECREF(l);
            return NULL;
        }
        PyList_SetItem(l, i, x);
    }
    return l;
#endif
}

#endif