[3.12] gh-109972: Split test_gdb.py into test_gdb package (#109977) (#110339)

gh-109972: Split test_gdb.py into test_gdb package (#109977)

Split test_gdb.py file into a test_gdb package made of multiple
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.
  Update get_sample_script(): use __file__ to locate gdb_sample.py.
* Move gdb_has_frame_select() and HAS_PYUP_PYDOWN to test_misc.py.
* Explicitly skip test_gdb on Windows. Previously, test_gdb was
  skipped even if gdb was available because of
  gdb_has_frame_select().

(cherry picked from commit 8f324b7ecd)

Lib/test/test_gdb/test_cfunction.py

@@ -0,0 +1,83 @@
+import re
+import textwrap
+import unittest
+from test import support
+from test.support import python_is_optimized
+
+from .util import setup_module, DebuggerTests
+
+
+def setUpModule():
+    setup_module()
+
+
+@unittest.skipIf(python_is_optimized(),
+                 "Python was compiled with optimizations")
+@support.requires_resource('cpu')
+class CFunctionTests(DebuggerTests):
+    # 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 test_pycfunction(self):
+        'Verify that "py-bt" displays invocations of PyCFunction instances'
+        # 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.
+        expected_frame = r'#(1|2)'
+        # Various optimizations multiply the code paths by which these are
+        # called, so test a variety of calling conventions.
+        for func_name, args in (
+            ('meth_varargs', ''),
+            ('meth_varargs_keywords', ''),
+            ('meth_o', '[]'),
+            ('meth_noargs', ''),
+            ('meth_fastcall', ''),
+            ('meth_fastcall_keywords', ''),
+        ):
+            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}'):
+                    cmd = textwrap.dedent(f'''
+                        import _testcapi
+                        def foo():
+                            {obj}.{func_name}({args})
+                        def bar():
+                            foo()
+                        bar()
+                    ''')
+                    # 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,
+                    )
+                    regex = expected_frame
+                    regex += re.escape(f' <built-in method {func_name}')
+                    self.assertRegex(gdb_output, regex)