[3.12] gh-109972: Enhance test_gdb (#110026) (#110351)

* gh-109972: Enhance test_gdb (#110026)

* Split test_pycfunction.py: add test_cfunction_full.py.
  Split the function into the following 6 functions. In verbose
  mode, these "pycfunction" tests now log each tested call.

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

* Move get_gdb_repr() to PrettyPrintTests.
* Replace DebuggerTests.get_sample_script() with SAMPLE_SCRIPT.
* Rename checkout_hook_path to CHECKOUT_HOOK_PATH.
* Rename gdb_version to GDB_VERSION_TEXT.
* Replace (gdb_major_version, gdb_minor_version) with GDB_VERSION.
* run_gdb() uses "backslashreplace" error handler instead of "replace".
* Add check_gdb() function to util.py.
* Enhance support.check_cflags_pgo(): check also for sysconfig
  PGO_PROF_USE_FLAG (if available) in compiler flags.
* Move some SkipTest checks to test_gdb/__init__.py.
* Elaborate why gdb cannot be tested on Windows: gdb doesn't support
  PDB debug symbol files.

(cherry picked from commit 757cbd4f29)

* gh-104736: Fix test_gdb tests on ppc64le with clang (#109360)

Fix test_gdb on Python built with LLVM clang 16 on Linux ppc64le (ex:
Fedora 38). Search patterns in gdb "bt" command output to detect
when gdb fails to retrieve the traceback. For example, skip a test if
"Backtrace stopped: frame did not save the PC" is found.

(cherry picked from commit 44d9a71ea2)

* gh-110166: Fix gdb CFunctionFullTests on ppc64le clang build (#110331)

CFunctionFullTests now also runs "bt" command before "py-bt-full",
similar to CFunctionTests which also runs "bt" command before
"py-bt". So test_gdb can skip the test if patterns like "?? ()" are
found in the gdb output.

(cherry picked from commit 1de9406f91)

Lib/test/test_gdb/test_cfunction.py

@@ -1,8 +1,6 @@
-import re
 import textwrap
 import unittest
 from test import support
-from test.support import python_is_optimized
 
 from .util import setup_module, DebuggerTests
 
@@ -11,10 +9,22 @@ def setUpModule():
     setup_module()
 
 
-@unittest.skipIf(python_is_optimized(),
+@unittest.skipIf(support.python_is_optimized(),
                  "Python was compiled with optimizations")
 @support.requires_resource('cpu')
 class CFunctionTests(DebuggerTests):
+    def check(self, func_name, cmd):
+        # 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)
+
     # 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
@@ -24,60 +34,52 @@ class CFunctionTests(DebuggerTests):
     # 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):
+    def check_pycfunction(self, func_name, args):
         '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)'
+
+        if support.verbose:
+            print()
+
         # 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()',
         ):
-            for obj in (
-                '_testcapi',
-                '_testcapi.MethClass',
-                '_testcapi.MethClass()',
-                '_testcapi.MethStatic()',
+            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)
 
-                # 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)
+                self.check(func_name, cmd)
 
-                    # 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)
+    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', '')