bpo-39849: Fix compiler warning in _testcapimodule

[shihai1991]

https://bugs.python.org/issue39849

[corona10]

LGTM, I 've checked on my local machone, no warning is now showing.

[corona10]

@serhiy-storchaka @vstinner Please take a look.

[corona10]

@serhiy-storchaka I will merge it after my mentor's approval :) cc @vstinner

[vstinner]

If I recall correctly, (void) res; doesn't silence the warning in some cases. Sorry, I don't recall in which case (which compiler, which compiler flags). Maybe it's enough for most cases.

I'm unhappy with the fix: _testcapi.test_buildvalue_issue38913() ensures that Py_BuildValue() returns NULL and raises an exception. If it's not the case, the test must fail.

For me, the assertion is part of the test and _testcapi must never be compiled without assertions.

@shihai1991: Can you please write a different PR which ensure that _testcapimodule.c and _testinternalcapi.c always enable assertions? Just put the following code at the top:

/* Always enable assertions */
#undef NDEBUG

[shihai1991]

If I recall correctly, (void) res; doesn't silence the warning in some cases. Sorry, I don't recall in which case (which compiler, which compiler flags). Maybe it's enough for most cases.

I'm unhappy with the fix: _testcapi.test_buildvalue_issue38913() ensures that Py_BuildValue() returns NULL and raises an exception. If it's not the case, the test must fail.

For me, the assertion is part of the test and _testcapi must never be compiled without assertions.

@shihai1991: Can you please write a different PR which ensure that _testcapimodule.c and _testinternalcapi.c always enable assertions? Just put the following code at the top:

/* Always enable assertions */
#undef NDEBUG

Sure, let me try it ;)

[shihai1991]

@vstinner Hi, victor. I enable assertions in #19623

[vstinner]

@corona10: I suggest to merge PR #19623 instead, it's a more generic solution and it may help to catch more bugs in release builds. You can merge PR #19623 if you want.