https://github.com/python/cpython/commit/79195df23c694770b3b03ff90b90ae734f930cb7 commit: 79195df23c694770b3b03ff90b90ae734f930cb7 branch: 3.14 author: Miss Islington (bot) <[email protected]> committer: kumaraditya303 <[email protected]> date: 2025-11-13T17:23:22+05:30 summary:
[3.14] gh-140260: fix data race in `_struct` module initialization with subinterpreters (GH-140909) (#141501) gh-140260: fix data race in `_struct` module initialization with subinterpreters (GH-140909) (cherry picked from commit 63548b36998e7f7cd5c7c28b53b348a93f836737) Co-authored-by: Shamil <[email protected]> files: A Misc/NEWS.d/next/Core_and_Builtins/2025-11-02-15-28-33.gh-issue-140260.JNzlGz.rst M Lib/test/test_struct.py M Modules/_struct.c M Tools/c-analyzer/cpython/ignored.tsv diff --git a/Lib/test/test_struct.py b/Lib/test/test_struct.py index 75c76a36ee92f5..cceecdd526c006 100644 --- a/Lib/test/test_struct.py +++ b/Lib/test/test_struct.py @@ -800,6 +800,23 @@ def test_c_complex_round_trip(self): round_trip = struct.unpack(f, struct.pack(f, z))[0] self.assertComplexesAreIdentical(z, round_trip) + @unittest.skipIf( + support.is_android or support.is_apple_mobile, + "Subinterpreters are not supported on Android and iOS" + ) + def test_endian_table_init_subinterpreters(self): + # Verify that the _struct extension module can be initialized + # concurrently in subinterpreters (gh-140260). + try: + from concurrent.futures import InterpreterPoolExecutor + except ImportError: + raise unittest.SkipTest("InterpreterPoolExecutor not available") + + code = "import struct" + with InterpreterPoolExecutor(max_workers=5) as executor: + results = executor.map(exec, [code] * 5) + self.assertListEqual(list(results), [None] * 5) + class UnpackIteratorTest(unittest.TestCase): """ diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-11-02-15-28-33.gh-issue-140260.JNzlGz.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-11-02-15-28-33.gh-issue-140260.JNzlGz.rst new file mode 100644 index 00000000000000..96bf9b51e4862c --- /dev/null +++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-11-02-15-28-33.gh-issue-140260.JNzlGz.rst @@ -0,0 +1,2 @@ +Fix :mod:`struct` data race in endian table initialization with +subinterpreters. Patch by Shamil Abdulaev. diff --git a/Modules/_struct.c b/Modules/_struct.c index 3fad35a8c94ee2..dc50c167641f5e 100644 --- a/Modules/_struct.c +++ b/Modules/_struct.c @@ -9,6 +9,7 @@ #include "Python.h" #include "pycore_bytesobject.h" // _PyBytesWriter +#include "pycore_lock.h" // _PyOnceFlag_CallOnce() #include "pycore_long.h" // _PyLong_AsByteArray() #include "pycore_moduleobject.h" // _PyModule_GetState() #include "pycore_weakref.h" // FT_CLEAR_WEAKREFS() @@ -1505,6 +1506,53 @@ static formatdef lilendian_table[] = { {0} }; +/* Ensure endian table optimization happens exactly once across all interpreters */ +static _PyOnceFlag endian_tables_init_once = {0}; + +static int +init_endian_tables(void *Py_UNUSED(arg)) +{ + const formatdef *native = native_table; + formatdef *other, *ptr; +#if PY_LITTLE_ENDIAN + other = lilendian_table; +#else + other = bigendian_table; +#endif + /* Scan through the native table, find a matching + entry in the endian table and swap in the + native implementations whenever possible + (64-bit platforms may not have "standard" sizes) */ + while (native->format != '\0' && other->format != '\0') { + ptr = other; + while (ptr->format != '\0') { + if (ptr->format == native->format) { + /* Match faster when formats are + listed in the same order */ + if (ptr == other) + other++; + /* Only use the trick if the + size matches */ + if (ptr->size != native->size) + break; + /* Skip float and double, could be + "unknown" float format */ + if (ptr->format == 'd' || ptr->format == 'f') + break; + /* Skip _Bool, semantics are different for standard size */ + if (ptr->format == '?') + break; + ptr->pack = native->pack; + ptr->unpack = native->unpack; + break; + } + ptr++; + } + native++; + } + return 0; +} + static const formatdef * whichtable(const char **pfmt) @@ -2713,47 +2761,8 @@ _structmodule_exec(PyObject *m) return -1; } - /* Check endian and swap in faster functions */ - { - const formatdef *native = native_table; - formatdef *other, *ptr; -#if PY_LITTLE_ENDIAN - other = lilendian_table; -#else - other = bigendian_table; -#endif - /* Scan through the native table, find a matching - entry in the endian table and swap in the - native implementations whenever possible - (64-bit platforms may not have "standard" sizes) */ - while (native->format != '\0' && other->format != '\0') { - ptr = other; - while (ptr->format != '\0') { - if (ptr->format == native->format) { - /* Match faster when formats are - listed in the same order */ - if (ptr == other) - other++; - /* Only use the trick if the - size matches */ - if (ptr->size != native->size) - break; - /* Skip float and double, could be - "unknown" float format */ - if (ptr->format == 'd' || ptr->format == 'f') - break; - /* Skip _Bool, semantics are different for standard size */ - if (ptr->format == '?') - break; - ptr->pack = native->pack; - ptr->unpack = native->unpack; - break; - } - ptr++; - } - native++; - } - } + /* init cannot fail */ + (void)_PyOnceFlag_CallOnce(&endian_tables_init_once, init_endian_tables, NULL); /* Add some symbolic constants to the module */ state->StructError = PyErr_NewException("struct.error", NULL, NULL); diff --git a/Tools/c-analyzer/cpython/ignored.tsv b/Tools/c-analyzer/cpython/ignored.tsv index 687871068e8bae..ba9119a06d57e2 100644 --- a/Tools/c-analyzer/cpython/ignored.tsv +++ b/Tools/c-analyzer/cpython/ignored.tsv @@ -24,6 +24,7 @@ Modules/posixmodule.c os_dup2_impl dup3_works - ## guards around resource init Python/thread_pthread.h PyThread__init_thread lib_initialized - +Modules/_struct.c - endian_tables_init_once - ##----------------------- ## other values (not Python-specific) _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
