macOS incompatibility

[outpaddling]

clang++ -O2 -I/Users/bacon/Pkgsrc/pkg/include -I/Users/bacon/Pkgsrc/pkg/include/eigen3 -I/Users/bacon/Pkgsrc/pkg/include/openblas_pthread -I/Users/bacon/Pkgsrc/pkg/include -DOPENBLAS -isystem/usr/local/opt/openblas/include -DNDEBUG -O3 -std=c++11 -isystem/usr/local/opt/openblas/include  -Icontrib/catch-1.9.7 -Isrc  -c -o src/debug.o src/debug.cpp
src/debug.cpp:108:24: error: no member named '__control' in 'fenv_t'
  108 |     old_excepts = fenv.__control & FE_ALL_EXCEPT;
      |                   ~~~~ ^
src/debug.cpp:111:10: error: no member named '__control' in 'fenv_t'            
  111 |     fenv.__control &= ~new_excepts;
      |     ~~~~ ^
src/debug.cpp:112:10: error: no member named '__mxcsr' in 'fenv_t'              
  112 |     fenv.__mxcsr   &= ~(new_excepts << 7);
      |     ~~~~ ^
src/debug.cpp:127:24: error: no member named '__control' in 'fenv_t'            
  127 |     old_excepts = fenv.__control & FE_ALL_EXCEPT;
      |                   ~~~~ ^
src/debug.cpp:130:10: error: no member named '__control' in 'fenv_t'            
  130 |     fenv.__control |= new_excepts;
      |     ~~~~ ^
src/debug.cpp:131:10: error: no member named '__mxcsr' in 'fenv_t'              
  131 |     fenv.__mxcsr   |= new_excepts << 7;
      |     ~~~~ ^
6 errors generated.                                                             
gmake: *** [<builtin>: src/debug.o] Error 1
*** Error code 2

Stop.
bmake[1]: stopped in /Users/bacon/Pkgsrc/pkgsrc/wip/gemma
*** Error code 1

Stop.
bmake: stopped in /Users/bacon/Pkgsrc/pkgsrc/wip/gemma
Darwin tarpon.acadix  bacon ~/Pkgsrc/pkgsrc/wip/gemma 1025: (pkgsrc): uname -a
Darwin tarpon.acadix.biz 24.0.0 Darwin Kernel Version 24.0.0: Mon Aug 12 20:49:48 PDT 2024; root:xnu-11215.1.10~2/RELEASE_ARM64_T8103 arm64

fenv_t is defined completely differently on different CPUs. You should probably not be accessing structure members directly, but using the interface functions documented in fenv(3).