gh-106078: Suppress the warning caused by multi-phase initialization of decimal

[CharlieZhao95]

>>> python -m test test_decimal Running Release|x64 interpreter... 0:00:00 Run tests sequentially 0:00:00 [1/1] test_decimal ...: warning: mpd_setminalloc: ignoring request to set MPD_MINALLOC a second time

This warnning is caused by the multi-phase initialization of decimal module. When decimal module is repeatedly imported, decimal_exec will be executed multiple times and this warning will be raised.

See #107287 (comment) for details.

• Issue: Isolate the _decimal extension module #106078

[CharlieZhao95]

Maybe we can skip news for this PR.

[CharlieZhao95]

It looks like the global variable check is failing, the tool cannot ignore static variables inside functions. Adding
__attribute__((constructor)) might be a more elegant option.
Forget this. Unfortunately, there is no equivalent for __attribute__((constructor)) on Windows.

[Eclips4]

I've tested it locally, and it works. Multiple imports of decimal doesn't make any warnings anymore.
LGTM.

[AlexWaygood]

The warning that's being suppressed here was recently brought up again in #110266

[erlend-aasland]

See also the discussion about a global init/exit API for extension modules.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot s390x RHEL7 LTO + PGO 3.x has failed when building commit de10522.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/244/builds/5628) and take a look at the build logs.
4. Check if the failure is related to this commit (de10522) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/244/builds/5628

Summary of the results of the build (if available):

==

Click to see traceback logs

Note: checking out 'de1052245f67d5c5a5dbb4f39449f7687f58fd78'. You are in 'detached HEAD' state. You can look around, make experimental changes and commit them, and you can discard any commits you make in this state without impacting any branches by performing another checkout. If you want to create a new branch to retain commits you create, you may do so (now or later) by using -b with the checkout command again. Example: git checkout -b new_branch_name HEAD is now at de10522... gh-106078: Suppress the warning caused by multi-phase initialization of `decimal` (#107524) Switched to and reset branch 'main' find: ‘build’: No such file or directoryfind: ‘build’: No such file or directoryfind: ‘build’: No such file or directoryfind: ‘build’: No such file or directorymake[2]: [clean-retain-profile] Error 1 (ignored)Python/instrumentation.c: In function ‘allocate_instrumentation_data’: Python/instrumentation.c:1497:9: warning: missing braces around initializer [-Wmissing-braces] code->_co_monitoring->local_monitors = (_Py_LocalMonitors){0 };^ Python/instrumentation.c:1497:9: warning: (near initialization for ‘(anonymous).tools’) [-Wmissing-braces] Python/instrumentation.c:1498:9: warning: missing braces around initializer [-Wmissing-braces] code->_co_monitoring->active_monitors = (_Py_LocalMonitors){0 };^ Python/instrumentation.c:1498:9: warning: (near initialization for ‘(anonymous).tools’) [-Wmissing-braces] Objects/bytes_methods.c: In function ‘find_internal’: Objects/bytes_methods.c:526:31: warning: ‘subobj’ may be used uninitialized in this function [-Wmaybe-uninitialized] if (PyObject_GetBuffer(subobj, &subbuf, PyBUF_SIMPLE) !=0) ^Objects/bytes_methods.c: In function ‘_Py_bytes_find’: Objects/bytes_methods.c:526:31: warning: ‘subobj’ may be used uninitialized in this function [-Wmaybe-uninitialized] Objects/bytes_methods.c:513:15: note: ‘subobj’ was declared here PyObject *subobj;^Objects/bytes_methods.c: In function ‘_Py_bytes_rfind’: Objects/bytes_methods.c:526:31: warning: ‘subobj’ may be used uninitialized in this function [-Wmaybe-uninitialized] if (PyObject_GetBuffer(subobj, &subbuf, PyBUF_SIMPLE) !=0) ^ Objects/bytes_methods.c:513:15: note: ‘subobj’ was declared here PyObject *subobj;^Objects/bytes_methods.c: In function ‘_Py_bytes_count’: Objects/bytes_methods.c:675:31: warning: ‘sub_obj’ may be used uninitialized in this function [-Wmaybe-uninitialized] if (PyObject_GetBuffer(sub_obj, &vsub, PyBUF_SIMPLE) !=0) ^Python/instrumentation.c: In function ‘allocate_instrumentation_data’: Python/instrumentation.c:1497:9: warning: missing braces around initializer [-Wmissing-braces] code->_co_monitoring->local_monitors = (_Py_LocalMonitors){0 };^ Python/instrumentation.c:1497:9: warning: (near initialization for ‘(anonymous).tools’) [-Wmissing-braces] Python/instrumentation.c:1498:9: warning: missing braces around initializer [-Wmissing-braces] code->_co_monitoring->active_monitors = (_Py_LocalMonitors){0 };^ Python/instrumentation.c:1498:9: warning: (near initialization for ‘(anonymous).tools’) [-Wmissing-braces] Python/pytime.c: In function ‘pytime_mul’: Python/pytime.c:1388:1: note: correcting inconsistent profile data } ^ ./Modules/_io/clinic/fileio.c.h: In function ‘_io_FileIO_close’: ./Modules/_io/fileio.c:175:32: warning: ‘exc’ may be used uninitialized in this function [-Wmaybe-uninitialized] _PyErr_ChainExceptions1(exc);^ ./Modules/_io/fileio.c:160:15: note: ‘exc’ was declared here PyObject *exc;^./Modules/_io/clinic/textio.c.h: In function ‘_io_TextIOWrapper_seek’: ./Modules/_io/textio.c:2601:45: warning: ‘MEM[(char *{ref-all})&cookie + 20B]’ may be used uninitialized in this function [-Wmaybe-uninitialized] decoded = PyObject_CallMethodObjArgs(self->decoder, &_Py_ID(decode), ^ ./Modules/_io/textio.c:2452:17: note: ‘MEM[(char *{ref-all})&cookie + 20B]’ was declared here cookie_type cookie;^ ./Modules/_io/textio.c:2610:54: warning: ‘MEM[(char *{ref-all})&cookie + 16B]’ may be used uninitialized in this function [-Wmaybe-uninitialized] if (PyUnicode_GetLength(self->decoded_chars) < cookie.chars_to_skip){^ ./Modules/_io/textio.c:2452:17: note: ‘MEM[(char *{ref-all})&cookie + 16B]’ was declared here cookie_type cookie;^ ./Modules/_io/textio.c:2420:40: warning: ‘MEM[(char *{ref-all})&cookie + 8B]’ may be used uninitialized in this function [-Wmaybe-uninitialized] return _textiowrapper_encoder_reset( ^ ./Modules/_io/textio.c:2452:17: note: ‘MEM[(char *{ref-all})&cookie + 8B]’ was declared here cookie_type cookie;^ ./Modules/_io/textio.c:2420:40: warning: ‘MEM[(char *{ref-all})&cookie]’ may be used uninitialized in this function [-Wmaybe-uninitialized] return _textiowrapper_encoder_reset( ^ ./Modules/_io/textio.c:2452:17: note: ‘MEM[(char *{ref-all})&cookie]’ was declared here cookie_type cookie;^make: *** [buildbottest] Error 5