pythongh-109972: Split test_gdb into a package of 3 tests

Split test_gdb.py file into a test_gdb package made 3 tests, so tests
can now be run in parallel.

* Create Lib/test/test_gdb/ directory.
* Split test_gdb.py into multiple files in Lib/test/test_gdb/
  directory.
* Move Lib/test/gdb_sample.py to Lib/test/test_gdb/ directory.
* Split PyBtTests.test_pycfunction() into 6 functions:

  * test_pycfunction_noargs()
  * test_pycfunction_o()
  * test_pycfunction_varargs()
  * test_pycfunction_varargs_keywords()
  * test_pycfunction_fastcall()
  * test_pycfunction_fastcall_keywords()

* In verbose mode, these "pycfunction" tests now log each tested
  call.

Author: vstinner

Lib/test/libregrtest/findtests.py

@@ -19,6 +19,7 @@
     "test_asyncio",
     "test_concurrent_futures",
     "test_future_stmt",
+    "test_gdb",
     "test_multiprocessing_fork",
     "test_multiprocessing_forkserver",
     "test_multiprocessing_spawn",

Lib/test/test_gdb.py

@@ -0,0 +1,10 @@
+# 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
+from test.support import load_package_tests
+
+def load_tests(*args):
+    return load_package_tests(os.path.dirname(__file__), *args)

Lib/test/test_gdb/__init__.py

@@ -0,0 +1,226 @@
+import re
+import textwrap
+import unittest
+
+from test import support
+from test.support import python_is_optimized
+
+from .util import (
+    CET_PROTECTION,
+    setup_module, DebuggerTests)
+
+
+def setUpModule():
+    setup_module()
+
+
+class PyBtTests(DebuggerTests):
+    @unittest.skipIf(python_is_optimized(),
+                     "Python was compiled with optimizations")
+    def test_bt(self):
+        'Verify that the "py-bt" command works'
+        bt = self.get_stack_trace(script=self.get_sample_script(),
+                                  cmds_after_breakpoint=['py-bt'])
+        self.assertMultilineMatches(bt,
+                                    r'''^.*
+Traceback \(most recent call first\):
+  <built-in method id of module object .*>
+  File ".*gdb_sample.py", line 10, in baz
+    id\(42\)
+  File ".*gdb_sample.py", line 7, in bar
+    baz\(a, b, c\)
+  File ".*gdb_sample.py", line 4, in foo
+    bar\(a=a, b=b, c=c\)
+  File ".*gdb_sample.py", line 12, in <module>
+    foo\(1, 2, 3\)
+''')
+
+    @unittest.skipIf(python_is_optimized(),
+                     "Python was compiled with optimizations")
+    def test_bt_full(self):
+        'Verify that the "py-bt-full" command works'
+        bt = self.get_stack_trace(script=self.get_sample_script(),
+                                  cmds_after_breakpoint=['py-bt-full'])
+        self.assertMultilineMatches(bt,
+                                    r'''^.*
+#[0-9]+ Frame 0x-?[0-9a-f]+, for file .*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 .*gdb_sample.py, line 4, in foo \(a=1, b=2, c=3\)
+    bar\(a=a, b=b, c=c\)
+#[0-9]+ Frame 0x-?[0-9a-f]+, for file .*gdb_sample.py, line 12, in <module> \(\)
+    foo\(1, 2, 3\)
+''')
+
+    @unittest.skipIf(python_is_optimized(),
+                     "Python was compiled with optimizations")
+    @support.requires_resource('cpu')
+    def test_threads(self):
+        'Verify that "py-bt" indicates threads that are waiting for the GIL'
+        cmd = '''
+from threading import Thread
+
+class TestThread(Thread):
+    # These threads would run forever, but we'll interrupt things with the
+    # debugger
+    def run(self):
+        i = 0
+        while 1:
+             i += 1
+
+t = {}
+for i in range(4):
+   t[i] = TestThread()
+   t[i].start()
+
+# Trigger a breakpoint on the main thread
+id(42)
+
+'''
+        # Verify with "py-bt":
+        gdb_output = self.get_stack_trace(cmd,
+                                          cmds_after_breakpoint=['thread apply all py-bt'])
+        self.assertIn('Waiting for the GIL', gdb_output)
+
+        # Verify with "py-bt-full":
+        gdb_output = self.get_stack_trace(cmd,
+                                          cmds_after_breakpoint=['thread apply all py-bt-full'])
+        self.assertIn('Waiting for the GIL', gdb_output)
+
+    @unittest.skipIf(python_is_optimized(),
+                     "Python was compiled with optimizations")
+    # Some older versions of gdb will fail with
+    #  "Cannot find new threads: generic error"
+    # unless we add LD_PRELOAD=PATH-TO-libpthread.so.1 as a workaround
+    def test_gc(self):
+        'Verify that "py-bt" indicates if a thread is garbage-collecting'
+        cmd = ('from gc import collect\n'
+               'id(42)\n'
+               'def foo():\n'
+               '    collect()\n'
+               'def bar():\n'
+               '    foo()\n'
+               'bar()\n')
+        # Verify with "py-bt":
+        gdb_output = self.get_stack_trace(cmd,
+                                          cmds_after_breakpoint=['break update_refs', 'continue', 'py-bt'],
+                                          )
+        self.assertIn('Garbage-collecting', gdb_output)
+
+        # Verify with "py-bt-full":
+        gdb_output = self.get_stack_trace(cmd,
+                                          cmds_after_breakpoint=['break update_refs', 'continue', 'py-bt-full'],
+                                          )
+        self.assertIn('Garbage-collecting', gdb_output)
+
+
+    @unittest.skipIf(python_is_optimized(),
+                     "Python was compiled with optimizations")
+    @support.requires_resource('cpu')
+    # Some older versions of gdb will fail with
+    #  "Cannot find new threads: generic error"
+    # unless we add LD_PRELOAD=PATH-TO-libpthread.so.1 as a workaround
+    #
+    # gdb will also generate many erroneous errors such as:
+    #     Function "meth_varargs" not defined.
+    # This is because we are calling functions from an "external" module
+    # (_testcapimodule) rather than compiled-in functions. It seems difficult
+    # to suppress these. See also the comment in DebuggerTests.get_stack_trace
+    def check_pycfunction(self, func_name, args):
+        'Verify that "py-bt" displays invocations of PyCFunction instances'
+
+        if support.verbose:
+            print()
+
+        # Various optimizations multiply the code paths by which these are
+        # called, so test a variety of calling conventions.
+        for obj in (
+            '_testcapi',
+            '_testcapi.MethClass',
+            '_testcapi.MethClass()',
+            '_testcapi.MethStatic()',
+
+            # XXX: bound methods don't yet give nice tracebacks
+            # '_testcapi.MethInstance()',
+        ):
+            with self.subTest(f'{obj}.{func_name}'):
+                call = f'{obj}.{func_name}({args})'
+                cmd = textwrap.dedent(f'''
+                    import _testcapi
+                    def foo():
+                        {call}
+                    def bar():
+                        foo()
+                    bar()
+                ''')
+                if support.verbose:
+                    print(f'  test call: {call}', flush=True)
+                # Verify with "py-bt":
+                gdb_output = self.get_stack_trace(
+                    cmd,
+                    breakpoint=func_name,
+                    cmds_after_breakpoint=['bt', 'py-bt'],
+                    # bpo-45207: Ignore 'Function "meth_varargs" not
+                    # defined.' message in stderr.
+                    ignore_stderr=True,
+                )
+                self.assertIn(f'<built-in method {func_name}', gdb_output)
+
+                # Verify with "py-bt-full":
+                gdb_output = self.get_stack_trace(
+                    cmd,
+                    breakpoint=func_name,
+                    cmds_after_breakpoint=['py-bt-full'],
+                    # bpo-45207: Ignore 'Function "meth_varargs" not
+                    # defined.' message in stderr.
+                    ignore_stderr=True,
+                )
+
+                # bpo-46600: If the compiler inlines _null_to_none() in
+                # meth_varargs() (ex: clang -Og), _null_to_none() is the
+                # frame #1. Otherwise, meth_varargs() is the frame #1.
+                regex = r'#(1|2)'
+                regex += re.escape(f' <built-in method {func_name}')
+                self.assertRegex(gdb_output, regex)
+
+    def test_pycfunction_noargs(self):
+        self.check_pycfunction('meth_noargs', '')
+
+    def test_pycfunction_o(self):
+        self.check_pycfunction('meth_o', '[]')
+
+    def test_pycfunction_varargs(self):
+        self.check_pycfunction('meth_varargs', '')
+
+    def test_pycfunction_varargs_keywords(self):
+        self.check_pycfunction('meth_varargs_keywords', '')
+
+    def test_pycfunction_fastcall(self):
+        self.check_pycfunction('meth_fastcall', '')
+
+    def test_pycfunction_fastcall_keywords(self):
+        self.check_pycfunction('meth_fastcall_keywords', '')
+
+    @unittest.skipIf(python_is_optimized(),
+                     "Python was compiled with optimizations")
+    def test_wrapper_call(self):
+        cmd = textwrap.dedent('''
+            class MyList(list):
+                def __init__(self):
+                    super(*[]).__init__()   # wrapper_call()
+
+            id("first break point")
+            l = MyList()
+        ''')
+        cmds_after_breakpoint = ['break wrapper_call', 'continue']
+        if CET_PROTECTION:
+            # bpo-32962: same case as in get_stack_trace():
+            # we need an additional 'next' command in order to read
+            # arguments of the innermost function of the call stack.
+            cmds_after_breakpoint.append('next')
+        cmds_after_breakpoint.append('py-bt')
+
+        # Verify with "py-bt":
+        gdb_output = self.get_stack_trace(cmd,
+                                          cmds_after_breakpoint=cmds_after_breakpoint)
+        self.assertRegex(gdb_output,
+                         r"<method-wrapper u?'__init__' of MyList object at ")