gh-117174: Skip test_gdb if Python is built with LTO

Add support.check_ldflags_lto().

Author: vstinner

Lib/test/libregrtest/utils.py

@@ -386,10 +386,11 @@ def get_build_info():
 
     # --with-lto
     optimizations = []
-    if '-flto=thin' in ldflags_nodist:
-        optimizations.append('ThinLTO')
-    elif '-flto' in ldflags_nodist:
-        optimizations.append('LTO')
+    if support.check_ldflags_lto():
+        if '-flto=thin' in ldflags_nodist:
+            optimizations.append('ThinLTO')
+        else:
+            optimizations.append('LTO')
 
     if support.check_cflags_pgo():
         # PGO (--enable-optimizations)

Lib/test/support/__init__.py

@@ -852,7 +852,7 @@ def python_is_optimized():
 def check_cflags_pgo():
     # Check if Python was built with ./configure --enable-optimizations:
     # with Profile Guided Optimization (PGO).
-    cflags_nodist = sysconfig.get_config_var('PY_CFLAGS_NODIST') or ''
+    cflags_nodist = (sysconfig.get_config_var('PY_CFLAGS_NODIST') or '')
     pgo_options = [
         # GCC
         '-fprofile-use',
@@ -867,13 +867,24 @@ def check_cflags_pgo():
     return any(option in cflags_nodist for option in pgo_options)
 
 
+def check_ldflags_lto():
+    # Check if Python was built with ./configure --with-lto:
+    # with Link Time Optimization (PGO).
+    ldflags_nodist = (sysconfig.get_config_var('PY_LDFLAGS_NODIST') or '')
+    lto_options = {
+        '-flto',
+        '-flto=thin',
+    }
+    return any(option in ldflags_nodist for option in lto_options)
+
+
 def check_bolt_optimized():
     # Always return false, if the platform is WASI,
     # because BOLT optimization does not support WASM binary.
     if is_wasi:
         return False
-    config_args = sysconfig.get_config_var('CONFIG_ARGS') or ''
-    return '--enable-bolt' in config_args
+    config_args = (sysconfig.get_config_var('CONFIG_ARGS') or '')
+    return ('--enable-bolt' in config_args)
 
 
 Py_GIL_DISABLED = bool(sysconfig.get_config_var('Py_GIL_DISABLED'))

Lib/test/test_gdb/__init__.py

@@ -24,6 +24,9 @@
 if support.check_cflags_pgo():
     raise unittest.SkipTest("test_gdb is not reliable on PGO builds")
 
+if support.check_ldflags_lto():
+    raise unittest.SkipTest("test_gdb is not reliable on LTO builds")
+
 if support.check_bolt_optimized():
     raise unittest.SkipTest("test_gdb is not reliable on BOLT optimized builds")
 

Lib/test/test_support.py

@@ -744,6 +744,11 @@ def test_get_signal_name(self):
             self.assertEqual(support.get_signal_name(exitcode), expected,
                              exitcode)
 
+    def test_compiler_flags(self):
+        self.assertIsInstance(support.check_cflags_pgo(), bool)
+        self.assertIsInstance(support.check_ldflags_lto(), bool)
+        self.assertIsInstance(support.check_bolt_optimized(), bool)
+
     # XXX -follows a list of untested API
     # make_legacy_pyc
     # is_resource_enabled

Misc/NEWS.d/next/Tests/2025-03-12-12-10-18.gh-issue-117174.J0vKxH.rst

@@ -0,0 +1,2 @@
+Skip test_gdb if Python is built with Link Time Optimization (LTO). Patch by
+Victor Stinner.