Fix build for macOS

[puddly]

pybind11 doesn't like to compile mixed C/C++ codebases with Clang: C++17 features are used but setting cxx_std=17 causes Clang to fail when compiling C source files, since -std=c++17 isn't valid when building C.

I've worked around this problem by patching the distutils compiler at build time on macOS:

$ python -m build --wheel
...
Successfully built pymicro_features-1.0.0-cp311-cp311-macosx_14_0_arm64.whl

[synesthesiam]

Would it work without the patch if we just renamed the .c files to .cc?

[puddly]

Converting them to C++ would require some patching:

pymicro-features/tensorflow/lite/experimental/microfrontend/lib/filterbank_util.cc:69:7: error: assigning to 'int16_t *' (aka 'short *') from incompatible type 'void *'
   69 |       malloc(num_channels_plus_1 * sizeof(*state->channel_frequency_starts));
      |       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pymicro-features/tensorflow/lite/experimental/microfrontend/lib/filterbank_util.cc:71:7: error: assigning to 'int16_t *' (aka 'short *') from incompatible type 'void *'
   71 |       malloc(num_channels_plus_1 * sizeof(*state->channel_weight_starts));
      |       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pymicro-features/tensorflow/lite/experimental/microfrontend/lib/filterbank_util.cc:73:7: error: assigning to 'int16_t *' (aka 'short *') from incompatible type 'void *'
   73 |       malloc(num_channels_plus_1 * sizeof(*state->channel_widths));
      |       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pymicro-features/tensorflow/lite/experimental/microfrontend/lib/filterbank_util.cc:74:17: error: assigning to 'uint64_t *' (aka 'unsigned long long *') from incompatible type 'void *'
   74 |   state->work = malloc(num_channels_plus_1 * sizeof(*state->work));
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pymicro-features/tensorflow/lite/experimental/microfrontend/lib/filterbank_util.cc:76:10: error: cannot initialize a variable of type 'float *' with an rvalue of type 'void *'
   76 |   float* center_mel_freqs =
      |          ^
   77 |       malloc(num_channels_plus_1 * sizeof(*center_mel_freqs));
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pymicro-features/tensorflow/lite/experimental/microfrontend/lib/filterbank_util.cc:78:12: error: cannot initialize a variable of type 'int16_t *' (aka 'short *') with an rvalue of type 'void *'
   78 |   int16_t* actual_channel_starts =
      |            ^
   79 |       malloc(num_channels_plus_1 * sizeof(*actual_channel_starts));
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pymicro-features/tensorflow/lite/experimental/microfrontend/lib/filterbank_util.cc:80:12: error: cannot initialize a variable of type 'int16_t *' (aka 'short *') with an rvalue of type 'void *'
   80 |   int16_t* actual_channel_widths =
      |            ^
   81 |       malloc(num_channels_plus_1 * sizeof(*actual_channel_widths));
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pymicro-features/tensorflow/lite/experimental/microfrontend/lib/filterbank_util.cc:163:20: error: assigning to 'int16_t *' (aka 'short *') from incompatible type 'void *'
  163 |   state->weights = calloc(weight_index_start, sizeof(*state->weights));
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pymicro-features/tensorflow/lite/experimental/microfrontend/lib/filterbank_util.cc:164:22: error: assigning to 'int16_t *' (aka 'short *') from incompatible type 'void *'
  164 |   state->unweights = calloc(weight_index_start, sizeof(*state->unweights));
      |                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
9 errors generated.
error: command '/usr/bin/clang++' failed with exit code 1

[domdomegg]

This fixes the build for me on an Apple Silicon device running macOS 14.6.1 ✅

It'd be great to see either this or #2 merged soon :)