Lib/test/test_gdb.py

# Verify that gdb can pretty-print the various PyObject* types
#
# The code for testing gdb was adapted from similar work in Unladen Swallow's
# Lib/test/test_jit_gdb.py

import os
import re
import subprocess
import sys
import unittest

from test.support import run_unittest

try:
    gdb_version, _ = subprocess.Popen(["gdb", "--version"],
                                      stdout=subprocess.PIPE).communicate()
except OSError:
    # This is what "no gdb" looks like.  There may, however, be other
    # errors that manifest this way too.
    raise unittest.SkipTest("Couldn't find gdb on the path")
gdb_version_number = re.search(b"^GNU gdb [^\d]*(\d+)\.", gdb_version)
if int(gdb_version_number.group(1)) < 7:
    raise unittest.SkipTest("gdb versions before 7.0 didn't support python embedding"
                            " Saw:\n" + gdb_version.decode('ascii', 'replace'))

# Verify that "gdb" was built with the embedded python support enabled:
cmd = "--eval-command=python import sys; print sys.version_info"
p = subprocess.Popen(["gdb", "--batch", cmd],
                     stdout=subprocess.PIPE)
gdbpy_version, _ = p.communicate()
if gdbpy_version == b'':
    raise unittest.SkipTest("gdb not built with embedded python support")

def gdb_has_frame_select():
    # Does this build of gdb have gdb.Frame.select ?
    cmd = "--eval-command=python print(dir(gdb.Frame))"
    p = subprocess.Popen(["gdb", "--batch", cmd],
                         stdout=subprocess.PIPE)
    stdout, _ = p.communicate()
    m = re.match(br'.*\[(.*)\].*', stdout)
    if not m:
        raise unittest.SkipTest("Unable to parse output from gdb.Frame.select test")
    gdb_frame_dir = m.group(1).split(b', ')
    return b"'select'" in gdb_frame_dir

HAS_PYUP_PYDOWN = gdb_has_frame_select()

class DebuggerTests(unittest.TestCase):

    """Test that the debugger can debug Python."""

    def run_gdb(self, *args):
        """Runs gdb with the command line given by *args.

        Returns its stdout, stderr
        """
        out, err = subprocess.Popen(
            args, stdout=subprocess.PIPE, stderr=subprocess.PIPE,
            ).communicate()
        return out, err

    def get_stack_trace(self, source=None, script=None,
                        breakpoint='PyObject_Print',
                        cmds_after_breakpoint=None,
                        import_site=False):
        '''
        Run 'python -c SOURCE' under gdb with a breakpoint.

        Support injecting commands after the breakpoint is reached

        Returns the stdout from gdb

        cmds_after_breakpoint: if provided, a list of strings: gdb commands
        '''
        # We use "set breakpoint pending yes" to avoid blocking with a:
        #   Function "foo" not defined.
        #   Make breakpoint pending on future shared library load? (y or [n])
        # error, which typically happens python is dynamically linked (the
        # breakpoints of interest are to be found in the shared library)
        # When this happens, we still get:
        #   Function "PyObject_Print" not defined.
        # emitted to stderr each time, alas.

        # Initially I had "--eval-command=continue" here, but removed it to
        # avoid repeated print breakpoints when traversing hierarchical data
        # structures

        # Generate a list of commands in gdb's language:
        commands = ['set breakpoint pending yes',
                    'break %s' % breakpoint,
                    'run']
        if cmds_after_breakpoint:
            commands += cmds_after_breakpoint
        else:
            commands += ['backtrace']

        # print commands

        # Use "commands" to generate the arguments with which to invoke "gdb":
        args = ["gdb", "--batch"]
        args += ['--eval-command=%s' % cmd for cmd in commands]
        args += ["--args",
                 sys.executable]

        if not import_site:
            # -S suppresses the default 'import site'
            args += ["-S"]

        if source:
            args += ["-c", source]
        elif script:
            args += [script]

        # print args
        # print ' '.join(args)

        # Use "args" to invoke gdb, capturing stdout, stderr:
        out, err = self.run_gdb(*args)

        # Ignore some noise on stderr due to the pending breakpoint:
        err = err.replace('Function "%s" not defined.\n' % breakpoint, '')

        # Ensure no unexpected error messages:
        self.assertEquals(err, '')

        return out

    def get_gdb_repr(self, source,
                     cmds_after_breakpoint=None,
                     import_site=False):
        # Given an input python source representation of data,
        # run "python -c'print DATA'" under gdb with a breakpoint on
        # PyObject_Print and scrape out gdb's representation of the "op"
        # parameter, and verify that the gdb displays the same string
        #
        # For a nested structure, the first time we hit the breakpoint will
        # give us the top-level structure
        gdb_output = self.get_stack_trace(source, breakpoint='PyObject_Print',
                                          cmds_after_breakpoint=cmds_after_breakpoint,
                                          import_site=import_site)
        # gdb can insert additional '\n' and space characters in various places
        # in its output, depending on the width of the terminal it's connected
        # to (using its "wrap_here" function)
        m = re.match('.*#0\s+PyObject_Print\s+\(\s*op\=\s*(.*?),\s+fp=.*\).*',
                     gdb_output, re.DOTALL)
        if not m:
            self.fail('Unexpected gdb output: %r\n%s' % (gdb_output, gdb_output))
        return m.group(1), gdb_output

    def assertEndsWith(self, actual, exp_end):
        '''Ensure that the given "actual" string ends with "exp_end"'''
        self.assert_(actual.endswith(exp_end),
                     msg='%r did not end with %r' % (actual, exp_end))

    def assertMultilineMatches(self, actual, pattern):
        m = re.match(pattern, actual, re.DOTALL)
        self.assert_(m,
                     msg='%r did not match %r' % (actual, pattern))

class PrettyPrintTests(DebuggerTests):
    def test_getting_backtrace(self):
        gdb_output = self.get_stack_trace('print 42')
        self.assertTrue('PyObject_Print' in gdb_output)

    def assertGdbRepr(self, val, cmds_after_breakpoint=None):
        # Ensure that gdb's rendering of the value in a debugged process
        # matches repr(value) in this process:
        gdb_repr, gdb_output = self.get_gdb_repr('print ' + repr(val),
                                                 cmds_after_breakpoint)
        self.assertEquals(gdb_repr, repr(val), gdb_output)

    def test_int(self):
        'Verify the pretty-printing of various "int" values'
        self.assertGdbRepr(42)
        self.assertGdbRepr(0)
        self.assertGdbRepr(-7)
        self.assertGdbRepr(sys.maxint)
        self.assertGdbRepr(-sys.maxint)

    def test_long(self):
        'Verify the pretty-printing of various "long" values'
        self.assertGdbRepr(0)
        self.assertGdbRepr(1000000000000)
        self.assertGdbRepr(-1)
        self.assertGdbRepr(-1000000000000000)

    def test_singletons(self):
        'Verify the pretty-printing of True, False and None'
        self.assertGdbRepr(True)
        self.assertGdbRepr(False)
        self.assertGdbRepr(None)

    def test_dicts(self):
        'Verify the pretty-printing of dictionaries'
        self.assertGdbRepr({})
        self.assertGdbRepr({'foo': 'bar'})
        self.assertGdbRepr({'foo': 'bar', 'douglas':42})

    def test_lists(self):
        'Verify the pretty-printing of lists'
        self.assertGdbRepr([])
        self.assertGdbRepr(range(5))

    def test_strings(self):
        'Verify the pretty-printing of strings'
        self.assertGdbRepr('')
        self.assertGdbRepr('And now for something hopefully the same')
        self.assertGdbRepr('string with embedded NUL here \0 and then some more text')
        self.assertGdbRepr('this is byte 255:\xff and byte 128:\x80')

    def test_tuples(self):
        'Verify the pretty-printing of tuples'
        self.assertGdbRepr(tuple())
        self.assertGdbRepr((1,))
        self.assertGdbRepr(('foo', 'bar', 'baz'))

    def test_unicode(self):
        'Verify the pretty-printing of unicode values'
        # Test the empty unicode string:
        self.assertGdbRepr('')

        self.assertGdbRepr('hello world')

        # Test printing a single character:
        #    U+2620 SKULL AND CROSSBONES
        self.assertGdbRepr('\u2620')

        # Test printing a Japanese unicode string
        # (I believe this reads "mojibake", using 3 characters from the CJK
        # Unified Ideographs area, followed by U+3051 HIRAGANA LETTER KE)
        self.assertGdbRepr('\u6587\u5b57\u5316\u3051')

        # Test a character outside the BMP:
        #    U+1D121 MUSICAL SYMBOL C CLEF
        # This is:
        # UTF-8: 0xF0 0x9D 0x84 0xA1
        # UTF-16: 0xD834 0xDD21
        try:
            # This will only work on wide-unicode builds:
            self.assertGdbRepr(chr(0x1D121))
        except ValueError as e:
            if e.message != 'chr() arg not in range(0x10000) (narrow Python build)':
                raise e

    def test_sets(self):
        'Verify the pretty-printing of sets'
        self.assertGdbRepr(set())
        self.assertGdbRepr(set(['a', 'b']))
        self.assertGdbRepr(set([4, 5, 6]))

        # Ensure that we handled sets containing the "dummy" key value,
        # which happens on deletion:
        gdb_repr, gdb_output = self.get_gdb_repr('''s = set(['a','b'])
s.pop()
print s''')
        self.assertEquals(gdb_repr, "set(['b'])")

    def test_frozensets(self):
        'Verify the pretty-printing of frozensets'
        self.assertGdbRepr(frozenset())
        self.assertGdbRepr(frozenset(['a', 'b']))
        self.assertGdbRepr(frozenset([4, 5, 6]))

    def test_exceptions(self):
        # Test a RuntimeError
        gdb_repr, gdb_output = self.get_gdb_repr('''
try:
    raise RuntimeError("I am an error")
except RuntimeError, e:
    print e
''')
        self.assertEquals(gdb_repr,
                          "exceptions.RuntimeError('I am an error',)")


        # Test division by zero:
        gdb_repr, gdb_output = self.get_gdb_repr('''
try:
    a = 1 / 0
except ZeroDivisionError, e:
    print e
''')
        self.assertEquals(gdb_repr,
                          "exceptions.ZeroDivisionError('integer division or modulo by zero',)")

    def test_classic_class(self):
        'Verify the pretty-printing of classic class instances'
        gdb_repr, gdb_output = self.get_gdb_repr('''
class Foo:
    pass
foo = Foo()
foo.an_int = 42
print foo''')
        m = re.match(r'<Foo\(an_int=42\) at remote 0x[0-9a-f]+>', gdb_repr)
        self.assertTrue(m,
                        msg='Unexpected classic-class rendering %r' % gdb_repr)

    def test_modern_class(self):
        'Verify the pretty-printing of new-style class instances'
        gdb_repr, gdb_output = self.get_gdb_repr('''
class Foo(object):
    pass
foo = Foo()
foo.an_int = 42
print foo''')
        m = re.match(r'<Foo\(an_int=42\) at remote 0x[0-9a-f]+>', gdb_repr)
        self.assertTrue(m,
                        msg='Unexpected new-style class rendering %r' % gdb_repr)

    def test_subclassing_list(self):
        'Verify the pretty-printing of an instance of a list subclass'
        gdb_repr, gdb_output = self.get_gdb_repr('''
class Foo(list):
    pass
foo = Foo()
foo += [1, 2, 3]
foo.an_int = 42
print foo''')
        m = re.match(r'<Foo\(an_int=42\) at remote 0x[0-9a-f]+>', gdb_repr)
        self.assertTrue(m,
                        msg='Unexpected new-style class rendering %r' % gdb_repr)

    def test_subclassing_tuple(self):
        'Verify the pretty-printing of an instance of a tuple subclass'
        # This should exercise the negative tp_dictoffset code in the
        # new-style class support
        gdb_repr, gdb_output = self.get_gdb_repr('''
class Foo(tuple):
    pass
foo = Foo((1, 2, 3))
foo.an_int = 42
print foo''')
        m = re.match(r'<Foo\(an_int=42\) at remote 0x[0-9a-f]+>', gdb_repr)
        self.assertTrue(m,
                        msg='Unexpected new-style class rendering %r' % gdb_repr)

    def assertSane(self, source, corruption, exp_type='unknown'):
        '''Run Python under gdb, corrupting variables in the inferior process
        immediately before taking a backtrace.

        Verify that the variable's representation is the expected failsafe
        representation'''
        if corruption:
            cmds_after_breakpoint=[corruption, 'backtrace']
        else:
            cmds_after_breakpoint=['backtrace']

        gdb_repr, gdb_output = \
            self.get_gdb_repr(source,
                              cmds_after_breakpoint=cmds_after_breakpoint)
        self.assertTrue(re.match('<%s at remote 0x[0-9a-f]+>' % exp_type,
                                 gdb_repr),
                        'Unexpected gdb representation: %r\n%s' % \
                            (gdb_repr, gdb_output))

    def test_NULL_ptr(self):
        'Ensure that a NULL PyObject* is handled gracefully'
        gdb_repr, gdb_output = (
            self.get_gdb_repr('print 42',
                              cmds_after_breakpoint=['set variable op=0',
                                                     'backtrace'])
            )

        self.assertEquals(gdb_repr, '0x0')

    def test_NULL_ob_type(self):
        'Ensure that a PyObject* with NULL ob_type is handled gracefully'
        self.assertSane('print 42',
                        'set op->ob_type=0')

    def test_corrupt_ob_type(self):
        'Ensure that a PyObject* with a corrupt ob_type is handled gracefully'
        self.assertSane('print 42',
                        'set op->ob_type=0xDEADBEEF')

    def test_corrupt_tp_flags(self):
        'Ensure that a PyObject* with a type with corrupt tp_flags is handled'
        self.assertSane('print 42',
                        'set op->ob_type->tp_flags=0x0',
                        exp_type='int')

    def test_corrupt_tp_name(self):
        'Ensure that a PyObject* with a type with corrupt tp_name is handled'
        self.assertSane('print 42',
                        'set op->ob_type->tp_name=0xDEADBEEF')

    def test_NULL_instance_dict(self):
        'Ensure that a PyInstanceObject with with a NULL in_dict is handled'
        self.assertSane('''
class Foo:
    pass
foo = Foo()
foo.an_int = 42
print foo''',
                        'set ((PyInstanceObject*)op)->in_dict = 0',
                        exp_type='Foo')

    def test_builtins_help(self):
        'Ensure that the new-style class _Helper in site.py can be handled'
        # (this was the issue causing tracebacks in
        #  http://bugs.python.org/issue8032#msg100537 )

        gdb_repr, gdb_output = self.get_gdb_repr('print __builtins__.help', import_site=True)
        m = re.match(r'<_Helper at remote 0x[0-9a-f]+>', gdb_repr)
        self.assertTrue(m,
                        msg='Unexpected rendering %r' % gdb_repr)

    def test_selfreferential_list(self):
        '''Ensure that a reference loop involving a list doesn't lead proxyval
        into an infinite loop:'''
        gdb_repr, gdb_output = \
            self.get_gdb_repr("a = [3, 4, 5] ; a.append(a) ; print a")

        self.assertEquals(gdb_repr, '[3, 4, 5, [...]]')

        gdb_repr, gdb_output = \
            self.get_gdb_repr("a = [3, 4, 5] ; b = [a] ; a.append(b) ; print a")

        self.assertEquals(gdb_repr, '[3, 4, 5, [[...]]]')

    def test_selfreferential_dict(self):
        '''Ensure that a reference loop involving a dict doesn't lead proxyval
        into an infinite loop:'''
        gdb_repr, gdb_output = \
            self.get_gdb_repr("a = {} ; b = {'bar':a} ; a['foo'] = b ; print a")

        self.assertEquals(gdb_repr, "{'foo': {'bar': {...}}}")

    def test_selfreferential_old_style_instance(self):
        gdb_repr, gdb_output = \
            self.get_gdb_repr('''
class Foo:
    pass
foo = Foo()
foo.an_attr = foo
print foo''')
        self.assertTrue(re.match('<Foo\(an_attr=<\.\.\.>\) at remote 0x[0-9a-f]+>',
                                 gdb_repr),
                        'Unexpected gdb representation: %r\n%s' % \
                            (gdb_repr, gdb_output))

    def test_selfreferential_new_style_instance(self):
        gdb_repr, gdb_output = \
            self.get_gdb_repr('''
class Foo(object):
    pass
foo = Foo()
foo.an_attr = foo
print foo''')
        self.assertTrue(re.match('<Foo\(an_attr=<\.\.\.>\) at remote 0x[0-9a-f]+>',
                                 gdb_repr),
                        'Unexpected gdb representation: %r\n%s' % \
                            (gdb_repr, gdb_output))

        gdb_repr, gdb_output = \
            self.get_gdb_repr('''
class Foo(object):
    pass
a = Foo()
b = Foo()
a.an_attr = b
b.an_attr = a
print a''')
        self.assertTrue(re.match('<Foo\(an_attr=<Foo\(an_attr=<\.\.\.>\) at remote 0x[0-9a-f]+>\) at remote 0x[0-9a-f]+>',
                                 gdb_repr),
                        'Unexpected gdb representation: %r\n%s' % \
                            (gdb_repr, gdb_output))

    def test_truncation(self):
        'Verify that very long output is truncated'
        gdb_repr, gdb_output = self.get_gdb_repr('print range(1000)')
        self.assertEquals(gdb_repr,
                          "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, "
                          "14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, "
                          "27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, "
                          "40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, "
                          "53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, "
                          "66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, "
                          "79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, "
                          "92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, "
                          "104, 105, 106, 107, 108, 109, 110, 111, 112, 113, "
                          "114, 115, 116, 117, 118, 119, 120, 121, 122, 123, "
                          "124, 125, 126, 127, 128, 129, 130, 131, 132, 133, "
                          "134, 135, 136, 137, 138, 139, 140, 141, 142, 143, "
                          "144, 145, 146, 147, 148, 149, 150, 151, 152, 153, "
                          "154, 155, 156, 157, 158, 159, 160, 161, 162, 163, "
                          "164, 165, 166, 167, 168, 169, 170, 171, 172, 173, "
                          "174, 175, 176, 177, 178, 179, 180, 181, 182, 183, "
                          "184, 185, 186, 187, 188, 189, 190, 191, 192, 193, "
                          "194, 195, 196, 197, 198, 199, 200, 201, 202, 203, "
                          "204, 205, 206, 207, 208, 209, 210, 211, 212, 213, "
                          "214, 215, 216, 217, 218, 219, 220, 221, 222, 223, "
                          "224, 225, 226...(truncated)")
        self.assertEquals(len(gdb_repr),
                          1024 + len('...(truncated)'))

    def test_builtin_function(self):
        gdb_repr, gdb_output = self.get_gdb_repr('print len')
        self.assertEquals(gdb_repr, '<built-in function len>')

    def test_builtin_method(self):
        gdb_repr, gdb_output = self.get_gdb_repr('import sys; print sys.stdout.readlines')
        self.assertTrue(re.match('<built-in method readlines of file object at remote 0x[0-9a-f]+>',
                                 gdb_repr),
                        'Unexpected gdb representation: %r\n%s' % \
                            (gdb_repr, gdb_output))

    def test_frames(self):
        gdb_output = self.get_stack_trace('''
def foo(a, b, c):
    pass

foo(3, 4, 5)
print foo.__code__''',
                                          breakpoint='PyObject_Print',
                                          cmds_after_breakpoint=['print (PyFrameObject*)(((PyCodeObject*)op)->co_zombieframe)']
                                          )
        self.assertTrue(re.match(r'.*\s+\$1 =\s+Frame 0x[0-9a-f]+, for file <string>, line 3, in foo \(\)\s+.*',
                                 gdb_output,
                                 re.DOTALL),
                        'Unexpected gdb representation: %r\n%s' % (gdb_output, gdb_output))

class PyListTests(DebuggerTests):
    def assertListing(self, expected, actual):
        self.assertEndsWith(actual, expected)

    def test_basic_command(self):
        'Verify that the "py-list" command works'
        bt = self.get_stack_trace(script='Lib/test/test_gdb_sample.py',
                                  cmds_after_breakpoint=['py-list'])

        self.assertListing('''
   5
   6    def bar(a, b, c):
   7        baz(a, b, c)
   8
   9    def baz(*args):
 >10        print(42)
  11
  12    foo(1, 2, 3)
''',
                      bt)

    def test_one_abs_arg(self):
        'Verify the "py-list" command with one absolute argument'
        bt = self.get_stack_trace(script='Lib/test/test_gdb_sample.py',
                                  cmds_after_breakpoint=['py-list 9'])

        self.assertListing('''
   9    def baz(*args):
 >10        print(42)
  11
  12    foo(1, 2, 3)
''',
                      bt)

    def test_two_abs_args(self):
        'Verify the "py-list" command with two absolute arguments'
        bt = self.get_stack_trace(script='Lib/test/test_gdb_sample.py',
                                  cmds_after_breakpoint=['py-list 1,3'])

        self.assertListing('''
   1    # Sample script for use by test_gdb.py
   2
   3    def foo(a, b, c):
''',
                      bt)

class StackNavigationTests(DebuggerTests):
    @unittest.skipUnless(HAS_PYUP_PYDOWN, "test requires py-up/py-down commands")
    def test_pyup_command(self):
        'Verify that the "py-up" command works'
        bt = self.get_stack_trace(script='Lib/test/test_gdb_sample.py',
                                  cmds_after_breakpoint=['py-up'])
        self.assertMultilineMatches(bt,
                                    r'''^.*
#[0-9]+ Frame 0x[0-9a-f]+, for file Lib/test/test_gdb_sample.py, line 7, in bar \(a=1, b=2, c=3\)
    baz\(a, b, c\)
$''')

    @unittest.skipUnless(HAS_PYUP_PYDOWN, "test requires py-up/py-down commands")
    def test_down_at_bottom(self):
        'Verify handling of "py-down" at the bottom of the stack'
        bt = self.get_stack_trace(script='Lib/test/test_gdb_sample.py',
                                  cmds_after_breakpoint=['py-down'])
        self.assertEndsWith(bt,
                            'Unable to find a newer python frame\n')

    @unittest.skipUnless(HAS_PYUP_PYDOWN, "test requires py-up/py-down commands")
    def test_up_at_top(self):
        'Verify handling of "py-up" at the top of the stack'
        bt = self.get_stack_trace(script='Lib/test/test_gdb_sample.py',
                                  cmds_after_breakpoint=['py-up'] * 4)
        self.assertEndsWith(bt,
                            'Unable to find an older python frame\n')

    @unittest.skipUnless(HAS_PYUP_PYDOWN, "test requires py-up/py-down commands")
    def test_up_then_down(self):
        'Verify "py-up" followed by "py-down"'
        bt = self.get_stack_trace(script='Lib/test/test_gdb_sample.py',
                                  cmds_after_breakpoint=['py-up', 'py-down'])
        self.assertMultilineMatches(bt,
                                    r'''^.*
#[0-9]+ Frame 0x[0-9a-f]+, for file Lib/test/test_gdb_sample.py, line 7, in bar \(a=1, b=2, c=3\)
    baz\(a, b, c\)
#[0-9]+ Frame 0x[0-9a-f]+, for file Lib/test/test_gdb_sample.py, line 10, in baz \(args=\(1, 2, 3\)\)
    print\(42\)
$''')

class PyBtTests(DebuggerTests):
    def test_basic_command(self):
        'Verify that the "py-bt" command works'
        bt = self.get_stack_trace(script='Lib/test/test_gdb_sample.py',
                                  cmds_after_breakpoint=['py-bt'])
        self.assertMultilineMatches(bt,
                                    r'''^.*
#[0-9]+ Frame 0x[0-9a-f]+, for file Lib/test/test_gdb_sample.py, line 7, in bar \(a=1, b=2, c=3\)
    baz\(a, b, c\)
#[0-9]+ Frame 0x[0-9a-f]+, for file Lib/test/test_gdb_sample.py, line 4, in foo \(a=1, b=2, c=3\)
    bar\(a, b, c\)
#[0-9]+ Frame 0x[0-9a-f]+, for file Lib/test/test_gdb_sample.py, line 12, in <module> \(\)
foo\(1, 2, 3\)
''')

class PyPrintTests(DebuggerTests):
    def test_basic_command(self):
        'Verify that the "py-print" command works'
        bt = self.get_stack_trace(script='Lib/test/test_gdb_sample.py',
                                  cmds_after_breakpoint=['py-print args'])
        self.assertMultilineMatches(bt,
                                    r".*\nlocal 'args' = \(1, 2, 3\)\n.*")

    @unittest.skipUnless(HAS_PYUP_PYDOWN, "test requires py-up/py-down commands")
    def test_print_after_up(self):
        bt = self.get_stack_trace(script='Lib/test/test_gdb_sample.py',
                                  cmds_after_breakpoint=['py-up', 'py-print c', 'py-print b', 'py-print a'])
        self.assertMultilineMatches(bt,
                                    r".*\nlocal 'c' = 3\nlocal 'b' = 2\nlocal 'a' = 1\n.*")

    def test_printing_global(self):
        bt = self.get_stack_trace(script='Lib/test/test_gdb_sample.py',
                                  cmds_after_breakpoint=['py-print __name__'])
        self.assertMultilineMatches(bt,
                                    r".*\nglobal '__name__' = '__main__'\n.*")

    def test_printing_builtin(self):
        bt = self.get_stack_trace(script='Lib/test/test_gdb_sample.py',
                                  cmds_after_breakpoint=['py-print len'])
        self.assertMultilineMatches(bt,
                                    r".*\nbuiltin 'len' = <built-in function len>\n.*")

class PyLocalsTests(DebuggerTests):
    def test_basic_command(self):
        bt = self.get_stack_trace(script='Lib/test/test_gdb_sample.py',
                                  cmds_after_breakpoint=['py-locals'])
        self.assertMultilineMatches(bt,
                                    r".*\nargs = \(1, 2, 3\)\n.*")

    @unittest.skipUnless(HAS_PYUP_PYDOWN, "test requires py-up/py-down commands")
    def test_locals_after_up(self):
        bt = self.get_stack_trace(script='Lib/test/test_gdb_sample.py',
                                  cmds_after_breakpoint=['py-up', 'py-locals'])
        self.assertMultilineMatches(bt,
                                    r".*\na = 1\nb = 2\nc = 3\n.*")

def test_main():
    run_unittest(#PrettyPrintTests,
                 #PyListTests,
                 #StackNavigationTests,
                 #PyBtTests,
                 #PyPrintTests,
                 #PyLocalsTests
                 )

if __name__ == "__main__":
    test_main()