add a SETUP_WITH opcode
It speeds up the with statement and correctly looks up the special
methods involved.
diff --git a/Doc/library/dis.rst b/Doc/library/dis.rst
index 6b7ed1e..9bd65dd 100644
--- a/Doc/library/dis.rst
+++ b/Doc/library/dis.rst
@@ -532,6 +532,18 @@
the names of the base classes, and TOS2 the class name.
+.. opcode:: SETUP_WITH (delta)
+
+ This opcode performs several operations before a with block starts. First,
+ it loads :meth:`~object.__exit__` from the context manager and pushes it onto
+ the stack for later use by :opcode:`WITH_CLEANUP`. Then,
+ :meth:`~object.__enter__` is called, and a finally block pointing to *delta*
+ is pushed. Finally, the result of calling the enter method is pushed onto
+ the stack. The next opcode will either ignore it (:opcode:`POP_TOP`), or
+ store it in (a) variable(s) (:opcode:`STORE_FAST`, :opcode:`STORE_NAME`, or
+ :opcode:`UNPACK_SEQUENCE`).
+
+
.. opcode:: WITH_CLEANUP ()
Cleans up the stack when a :keyword:`with` statement block exits. On top of
diff --git a/Doc/reference/compound_stmts.rst b/Doc/reference/compound_stmts.rst
index 3c716b2..afb7ebc 100644
--- a/Doc/reference/compound_stmts.rst
+++ b/Doc/reference/compound_stmts.rst
@@ -339,6 +339,8 @@
#. The context expression is evaluated to obtain a context manager.
+#. The context manager's :meth:`__exit__` is loaded for later use.
+
#. The context manager's :meth:`__enter__` method is invoked.
#. If a target was included in the :keyword:`with` statement, the return value
@@ -349,7 +351,7 @@
The :keyword:`with` statement guarantees that if the :meth:`__enter__` method
returns without an error, then :meth:`__exit__` will always be called. Thus, if
an error occurs during the assignment to the target list, it will be treated the
- same as an error occurring within the suite would be. See step 5 below.
+ same as an error occurring within the suite would be. See step 6 below.
#. The suite is executed.
diff --git a/Include/opcode.h b/Include/opcode.h
index 36a35dc..9739782 100644
--- a/Include/opcode.h
+++ b/Include/opcode.h
@@ -141,8 +141,10 @@
#define CALL_FUNCTION_KW 141 /* #args + (#kwargs<<8) */
#define CALL_FUNCTION_VAR_KW 142 /* #args + (#kwargs<<8) */
+#define SETUP_WITH 143
+
/* Support for opargs more than 16 bits long */
-#define EXTENDED_ARG 143
+#define EXTENDED_ARG 145
enum cmp_op {PyCmp_LT=Py_LT, PyCmp_LE=Py_LE, PyCmp_EQ=Py_EQ, PyCmp_NE=Py_NE, PyCmp_GT=Py_GT, PyCmp_GE=Py_GE,
diff --git a/Lib/opcode.py b/Lib/opcode.py
index 24d5dcc..7c3962d 100644
--- a/Lib/opcode.py
+++ b/Lib/opcode.py
@@ -181,7 +181,10 @@
def_op('CALL_FUNCTION_VAR', 140) # #args + (#kwargs << 8)
def_op('CALL_FUNCTION_KW', 141) # #args + (#kwargs << 8)
def_op('CALL_FUNCTION_VAR_KW', 142) # #args + (#kwargs << 8)
-def_op('EXTENDED_ARG', 143)
-EXTENDED_ARG = 143
+
+jrel_op('SETUP_WITH', 143)
+
+def_op('EXTENDED_ARG', 145)
+EXTENDED_ARG = 145
del def_op, name_op, jrel_op, jabs_op
diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index c7989b1..627f8aa 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -1689,6 +1689,7 @@
return isinstance(int, obj)
def do_issubclass(obj):
return issubclass(int, obj)
+ def swallow(*args): pass
# It would be nice to have every special method tested here, but I'm
# only listing the ones I can remember outside of typeobject.c, since it
@@ -1702,11 +1703,8 @@
("__instancecheck__", do_isinstance, return_true, set(), {}),
("__subclasscheck__", do_issubclass, return_true,
set(("__bases__",)), {}),
- # These two fail because the compiler generates LOAD_ATTR to look
- # them up. We'd have to add a new opcode to fix this, and it's
- # probably not worth it.
- # ("__enter__", run_context, iden),
- # ("__exit__", run_context, iden),
+ ("__enter__", run_context, iden, set(), {"__exit__" : swallow}),
+ ("__exit__", run_context, swallow, set(), {"__enter__" : iden}),
]
class Checker(object):
diff --git a/Misc/NEWS b/Misc/NEWS
index 5526d9c..a6b5fce 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@
Core and Builtins
-----------------
+- Issue #6101: A new opcode, SETUP_WITH, has been added to speed up the with
+ statement and correctly lookup the __enter__ and __exit__ special methods.
+
- Issue #5829: complex("1e500") no longer raises OverflowError. This
makes it consistent with float("1e500") and interpretation of real
and imaginary literals.
diff --git a/Python/ceval.c b/Python/ceval.c
index 4f0877b..92021e6 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -128,6 +128,7 @@
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"
@@ -2467,6 +2468,33 @@
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 the finally block before pushing the result
+ of __enter__ on the stack. */
+ PyFrame_BlockSetup(f, SETUP_FINALLY, INSTR_OFFSET() + oparg,
+ STACK_LEVEL());
+
+ PUSH(x);
+ continue;
+ }
+
case WITH_CLEANUP:
{
/* At the top of the stack are 1-3 values indicating
@@ -3171,6 +3199,24 @@
}
+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) {
diff --git a/Python/compile.c b/Python/compile.c
index 8c85306..e263d76 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -778,6 +778,8 @@
return -1;
case BREAK_LOOP:
return 0;
+ case SETUP_WITH:
+ return 1;
case WITH_CLEANUP:
return -1; /* XXX Sometimes more */
case LOAD_LOCALS:
@@ -2821,80 +2823,31 @@
static int
compiler_with(struct compiler *c, stmt_ty s)
{
- static identifier enter_attr, exit_attr;
basicblock *block, *finally;
- identifier tmpvalue = NULL;
assert(s->kind == With_kind);
- if (!enter_attr) {
- enter_attr = PyString_InternFromString("__enter__");
- if (!enter_attr)
- return 0;
- }
- if (!exit_attr) {
- exit_attr = PyString_InternFromString("__exit__");
- if (!exit_attr)
- return 0;
- }
-
block = compiler_new_block(c);
finally = compiler_new_block(c);
if (!block || !finally)
return 0;
- if (s->v.With.optional_vars) {
- /* Create a temporary variable to hold context.__enter__().
- We need to do this rather than preserving it on the stack
- because SETUP_FINALLY remembers the stack level.
- We need to do the assignment *inside* the try/finally
- so that context.__exit__() is called when the assignment
- fails. But we need to call context.__enter__() *before*
- the try/finally so that if it fails we won't call
- context.__exit__().
- */
- tmpvalue = compiler_new_tmpname(c);
- if (tmpvalue == NULL)
- return 0;
- PyArena_AddPyObject(c->c_arena, tmpvalue);
- }
-
/* Evaluate EXPR */
VISIT(c, expr, s->v.With.context_expr);
+ ADDOP_JREL(c, SETUP_WITH, finally);
- /* Squirrel away context.__exit__ by stuffing it under context */
- ADDOP(c, DUP_TOP);
- ADDOP_O(c, LOAD_ATTR, exit_attr, names);
- ADDOP(c, ROT_TWO);
-
- /* Call context.__enter__() */
- ADDOP_O(c, LOAD_ATTR, enter_attr, names);
- ADDOP_I(c, CALL_FUNCTION, 0);
-
- if (s->v.With.optional_vars) {
- /* Store it in tmpvalue */
- if (!compiler_nameop(c, tmpvalue, Store))
- return 0;
- }
- else {
- /* Discard result from context.__enter__() */
- ADDOP(c, POP_TOP);
- }
-
- /* Start the try block */
- ADDOP_JREL(c, SETUP_FINALLY, finally);
-
+ /* SETUP_WITH pushes a finally block. */
compiler_use_next_block(c, block);
if (!compiler_push_fblock(c, FINALLY_TRY, block)) {
return 0;
}
if (s->v.With.optional_vars) {
- /* Bind saved result of context.__enter__() to VAR */
- if (!compiler_nameop(c, tmpvalue, Load) ||
- !compiler_nameop(c, tmpvalue, Del))
- return 0;
- VISIT(c, expr, s->v.With.optional_vars);
+ VISIT(c, expr, s->v.With.optional_vars);
+ }
+ else {
+ /* Discard result from context.__enter__() */
+ ADDOP(c, POP_TOP);
}
/* BLOCK code */
diff --git a/Python/import.c b/Python/import.c
index 5e42e5c..88aced0 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -74,9 +74,10 @@
Python 2.7a0: 62171 (optimize list comprehensions/change LIST_APPEND)
Python 2.7a0: 62181 (optimize conditional branches:
introduce POP_JUMP_IF_FALSE and POP_JUMP_IF_TRUE)
+ Python 2.7a0 62191 (introduce SETUP_WITH)
.
*/
-#define MAGIC (62181 | ((long)'\r'<<16) | ((long)'\n'<<24))
+#define MAGIC (62191 | ((long)'\r'<<16) | ((long)'\n'<<24))
/* Magic word as global; note that _PyImport_Init() can change the
value of this global to accommodate for alterations of how the