Macでgcc compileを試みるもエラー`fatal error: byteswap.h: No such file or directory`

Macでgcc compileを試みるもエラー`fatal error: byteswap.h: No such file or directory`

```
fatal error: byteswap.h: No such file or directory
```

以下は例

```
$ pip install git+https://github.com/TadaoYamaoka/creversi
Collecting git+https://github.com/TadaoYamaoka/creversi
  Cloning https://github.com/TadaoYamaoka/creversi to /private/var/folders/hl/xrycfdz539d79hms3cqm94tr0000gn/T/pip-req-build-joxvj3kl
  Running command git clone -q https://github.com/TadaoYamaoka/creversi /private/var/folders/hl/xrycfdz539d79hms3cqm94tr0000gn/T/pip-req-build-joxvj3kl
Building wheels for collected packages: creversi
  Building wheel for creversi (setup.py) ... error
  ERROR: Complete output from command /anaconda3/bin/python -u -c 'import setuptools, tokenize;__file__='"'"'/private/var/folders/hl/xrycfdz539d79hms3cqm94tr0000gn/T/pip-req-build-joxvj3kl/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' bdist_wheel -d /private/var/folders/hl/xrycfdz539d79hms3cqm94tr0000gn/T/pip-wheel-cocr_r6e --python-tag cp37:
  ERROR: running bdist_wheel
  running build
  running build_py
  creating build
  creating build/lib.macosx-10.7-x86_64-3.7
  creating build/lib.macosx-10.7-x86_64-3.7/creversi
  copying creversi/__init__.py -> build/lib.macosx-10.7-x86_64-3.7/creversi
  copying creversi/GGF.py -> build/lib.macosx-10.7-x86_64-3.7/creversi
  creating build/lib.macosx-10.7-x86_64-3.7/creversi/gym_reversi
  copying creversi/gym_reversi/__init__.py -> build/lib.macosx-10.7-x86_64-3.7/creversi/gym_reversi
  creating build/lib.macosx-10.7-x86_64-3.7/creversi/gym_reversi/envs
  copying creversi/gym_reversi/envs/__init__.py -> build/lib.macosx-10.7-x86_64-3.7/creversi/gym_reversi/envs
  running build_ext
  cythoning creversi/creversi.pyx to creversi/creversi.cpp
  /anaconda3/lib/python3.7/site-packages/Cython/Compiler/Main.py:367: FutureWarning: Cython directive 'language_level' not set, using 2 for now (Py2). This will change in a later release! File: /private/var/folders/hl/xrycfdz539d79hms3cqm94tr0000gn/T/pip-req-build-joxvj3kl/creversi/creversi.pyx
    tree = Parsing.p_module(s, pxd, full_module_name)
  building 'creversi.creversi' extension
  creating build/temp.macosx-10.7-x86_64-3.7
  creating build/temp.macosx-10.7-x86_64-3.7/creversi
  creating build/temp.macosx-10.7-x86_64-3.7/creversi_cpp
  gcc -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -I/anaconda3/include -arch x86_64 -I/anaconda3/include -arch x86_64 -Icreversi_cpp -I/anaconda3/lib/python3.7/site-packages/numpy/core/include -I/anaconda3/include/python3.7m -c creversi/creversi.cpp -o build/temp.macosx-10.7-x86_64-3.7/creversi/creversi.o -std=c++11 -msse4.2 -mbmi -mbmi2 -mavx2
  cc1plus: warning: command line option '-Wstrict-prototypes' is valid for C/ObjC but not for C++
  In file included from /anaconda3/lib/python3.7/site-packages/numpy/core/include/numpy/ndarraytypes.h:1824,
                   from /anaconda3/lib/python3.7/site-packages/numpy/core/include/numpy/ndarrayobject.h:12,
                   from /anaconda3/lib/python3.7/site-packages/numpy/core/include/numpy/arrayobject.h:4,
                   from creversi/creversi.cpp:633:
  /anaconda3/lib/python3.7/site-packages/numpy/core/include/numpy/npy_1_7_deprecated_api.h:17:2: warning: #warning "Using deprecated NumPy API, disable it with " "#define NPY_NO_DEPRECATED_API NPY_1_7_API_VERSION" [-Wcpp]
     17 | #warning "Using deprecated NumPy API, disable it with " \
        |  ^~~~~~~
  In file included from creversi_cpp/utils.hpp:7,
                   from creversi/creversi.cpp:635:
  creversi_cpp/board.hpp:46:10: fatal error: byteswap.h: No such file or directory
     46 | #include <byteswap.h>
        |          ^~~~~~~~~~~~
  compilation terminated.
  error: command 'gcc' failed with exit status 1
  ----------------------------------------
  ERROR: Failed building wheel for creversi
  Running setup.py clean for creversi
Failed to build creversi
```

Macには`byteswap.h`の代わりに`machine/endian.h`というのがあるらしいのでこれを使用することで解決しているみたい。

```
diff --git a/creversi_cpp/board.hpp b/creversi_cpp/board.hpp
index bdd90f6..1cf6f24 100644
--- a/creversi_cpp/board.hpp
+++ b/creversi_cpp/board.hpp
@@ -43,8 +43,9 @@ unsigned char _bittestandreset64(long long *a, long long b)
 #define _mm256_set_m128i(v0, v1)  _mm256_insertf128_si256(_mm256_castsi128_si256(v1), (v0), 1)
 #define _mm256_setr_m128i(v0, v1) _mm256_set_m128i((v1), (v0))
 
-#include <byteswap.h>
-#define _byteswap_uint64(x) bswap_64(x)
+#include <machine/endian.h>
+//#include <byteswap.h>
+#define _byteswap_uint64(x) _bswap64(x)
 
 #define _rotr64 __rorq
 #endif
```

上記だとMac専用コードになってしまうので、ifdefで分岐させるのが良さそう
（本当に正しいやり方かどうかはわからないです）
>[cプリプロセッサでmac-os-x、ios、linux、windowsを確実に検出する方法/973125744/](https://www.it-swarm-ja.com/ja/c%2B%2B/cプリプロセッサでmac-os-x、ios、linux、windowsを確実に検出する方法/973125744/)
>[c-ifdef-mac-os-x-question](https://stackoverflow.com/questions/6802903/c-ifdef-mac-os-x-question)

>```
#ifdef __APPLE__
   // Mac専用の処理
#else
   // Mac以外の処理
#endif
```

# 参考
[Missing byteswap.h on MSVC and macOS #23](https://github.com/taocpp/taopq/issues/23)
> On macOS perhaps machine/endian.h or libkern/OSByteOrder.h could be used instead. We also have endian.hpp in the PEGTL which seems to work everywhere.
[cプリプロセッサでmac-os-x、ios、linux、windowsを確実に検出する方法/973125744/](https://www.it-swarm-ja.com/ja/c%2B%2B/cプリプロセッサでmac-os-x、ios、linux、windowsを確実に検出する方法/973125744/)
[c-ifdef-mac-os-x-question](https://stackoverflow.com/questions/6802903/c-ifdef-mac-os-x-question)