[MacPorts] #62488: py38-scipy - vodemodule.c - fatal error: 'threads.h' not found

[MacPorts]

#62488: py38-scipy -  vodemodule.c - fatal error: 'threads.h' not found
-------------------------+-----------------------
  Reporter:  dyne2meter  |      Owner:  michaelld
      Type:  defect      |     Status:  assigned
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:  2.6.4
Resolution:              |   Keywords:  elcapitan
      Port:  py-scipy    |
-------------------------+-----------------------

Comment (by michaelld):

 If I do `clang -std=c11 -dM -E - </dev/null | grep STDC` (Xcode 12.3 build
 version 12C33 or MP Clang 11) I see among others `#define
 __STDC_NO_THREADS__ 1` ... if I do the same with any MP GCC, I do ''not''
 see that `#define` which implies that I should be able to `#include
 <threads.h>` when using `-std=c11`. But, when I create a program that does
 just that it always fails, regardless of whether using Clang or GCC and
 what `std` I select. Maybe GCC isn't being honest in its capabilities
 self-assessment? Anyway, forcing this macro to be defined seems like the
 way to go here, and that seems to be an easy tweak to the SciPy code ...
 will commit once I've verified it locally.

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Ticket URL: <https://trac.macports.org/ticket/62488#comment:16>
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