perf trampoline segfaults on UBSan builds #161288

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1. NekoAsakura

   added

   buildThe build process and cross-buildThe build process and cross-build

   type-crashA hard crash of the interpreter, possibly with a core dumpA hard crash of the interpreter, possibly with a core dump

   interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

   on Nov 4, 2026
2. vstinner commented on Nov 4, 2026

   

   vstinner

   on Nov 4, 2026

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   test_perf_profiler is skipped on most sanitizers, and so it didn't catch this issue:

   if support.check_sanitizer(address=True, memory=True, ub=True, function=True):
       # gh-109580: Skip the test because it does crash randomly if Python is
       # built with ASAN.
       raise unittest.SkipTest("test crash randomly on ASAN/MSAN/UBSAN build")
3. vstinner commented on Nov 4, 2026

   

   vstinner

   on Nov 4, 2026

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   I don't think that it's worth it to bother with testing perf support in test_embed, so I suggest to skip tests on perf_profiling:

   diff --git a/Lib/test/test_embed.py b/Lib/test/test_embed.py
   index 65feb162b0c..c8cfbcac0fd 100644
   --- a/Lib/test/test_embed.py
   +++ b/Lib/test/test_embed.py
   @@ -1224,7 +1224,6 @@ def test_init_compat_env(self):
                'module_search_paths': self.IGNORE_CONFIG,
                'safe_path': True,
                'int_max_str_digits': 4567,
   -            'perf_profiling': 1,
            }
            if Py_STATS:
                config['_pystats'] = 1
   @@ -1261,7 +1260,6 @@ def test_init_python_env(self):
                'module_search_paths': self.IGNORE_CONFIG,
                'safe_path': True,
                'int_max_str_digits': 4567,
   -            'perf_profiling': 1,
            }
            if Py_STATS:
                config['_pystats'] = True
   @@ -1965,7 +1963,6 @@ def test_initconfig_api(self):
                'xoptions': {'faulthandler': True},
                'hash_seed': 10,
                'use_hash_seed': True,
   -            'perf_profiling': 2,
            }
            config_dev_mode(preconfig, config)
            # Temporarily enable ignore_stderr=True to ignore warnings on JIT builds
   diff --git a/Programs/_testembed.c b/Programs/_testembed.c
   index 08bbcd4cfec..8fcb4a92dcb 100644
   --- a/Programs/_testembed.c
   +++ b/Programs/_testembed.c
   @@ -845,7 +845,7 @@ static void set_most_env_vars(void)
    #ifdef Py_STATS
        putenv("PYTHONSTATS=1");
    #endif
   -    putenv("PYTHONPERFSUPPORT=1");
   +    // gh-161288: Do not set PYTHONPERFSUPPORT since it fails on UBSan builds
    }
    
    
   @@ -1724,9 +1724,7 @@ static int test_initconfig_api(void)
            goto error;
        }
    
   -    if (PyInitConfig_SetInt(config, "perf_profiling", 2) < 0) {
   -        goto error;
   -    }
   +    // gh-161288: Do not set "perf_profiling" since it fails on UBSan builds
    
        // Set a UTF-8 string (program_name)
        if (PyInitConfig_SetStr(config, "program_name", PROGRAM_NAME_UTF8) < 0) {
4. NekoAsakura commented on Nov 4, 2026

   

   NekoAsakura

   on Nov 4, 2026

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   The fix is not much bother, and we already have similar macros _Py_NO_SANITIZE_ADDRESS/THREAD/MEMORY.