py-numpy: @1.20.1: build error for macOS 10.12

[mascguy (Christopher Nielsen)]

py-numpy subports (including those for both Python 3.7 and 3.8), are failing on macOS 10.12.

Given that this appears to be occurring while checking for compiler features - what would normally be the configure phase - this ideally shouldn't cause the build to fail. Nonetheless, it does.

The apparent errors seen in the logs, are as follows. Whether this is the true underlying issue, though, isn't clear:

.../py37-numpy/work/numpy-numpy-8d9d768/numpy/distutils/checks/cpu_avx512_clx.c:6:17: error: implicit declaration of function '_mm512_dpbusd_epi32' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
    __m512i a = _mm512_dpbusd_epi32(_mm512_setzero_si512(), _mm512_setzero_si512(), _mm512_setzero_si512());
                ^
.../py37-numpy/work/numpy-numpy-8d9d768/numpy/distutils/checks/cpu_avx512_clx.c:6:17: note: did you mean '_mm512_abs_epi32'?
/Library/Developer/CommandLineTools/usr/lib/clang/9.0.0/include/avx512fintrin.h:1881:1: note: '_mm512_abs_epi32' declared here
_mm512_abs_epi32(__m512i __A)
^
.../py37-numpy/work/numpy-numpy-8d9d768/numpy/distutils/checks/cpu_avx512_clx.c:6:13: error: initializing '__m512i' (vector of 8 'long long' values) with an expression of incompatible type 'int'
    __m512i a = _mm512_dpbusd_epi32(_mm512_setzero_si512(), _mm512_setzero_si512(), _mm512_setzero_si512());
            ^   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2 errors generated.
CCompilerOpt.feature_test[1458] : testing failed

This is seen both in local testing, as well as on the macOS 10.12 builder:

​https://build.macports.org/builders/ports-10.12_x86_64-builder/builds/138564/steps/install-port/logs/stdio

That same log is also attached, to ensure it's not lost when build history is aged out.

[michaelld (Michael Dickens)]

Thanks for getting this ticket going. I'm updating my 10.12 buildbot & should be able to do live debugging starting tomorrow sometime. No idea what's going on ...

[mascguy (Christopher Nielsen)]

No problem Michael. And if you need any help with testing or diagnosis, I'm happy to fire up my 10.12 VM. Don't hesitate to give me a shout!

[michaelld (Michael Dickens)]

Yup I see this on my macOS 10.12 boot. That's strange that the errors seem to be causing "configure" to error out ... will investigate! Will give you a shout once I get something useful!