如果我pip install cffi，我得到这个：
building '_cffi_backend' extension
c:\mingw\bin\gcc.exe -mdll -O -Wall -Ic/libffi_msvc -IC:\python27\include -IC:\python27\PC -c c/_cffi_backend.c -o build\temp.win32-2.7\Release\c\_cffi_backend.o
...
(lots of warnings)
...
c/libffi_msvc\win32.c: In function 'ffi_call_x86':
c/libffi_msvc\win32.c:48:2: error: '_asm' undeclared (first use in this function)
c/libffi_msvc\win32.c:48:2: note: each undeclared identifier is reported only once for each function it appears in
c/libffi_msvc\win32.c:48:7: error: expected ';' before '{' token
c/libffi_msvc\win32.c:162:1: warning: control reaches end of non-void function [-Wreturn-type]
error: command 'gcc' failed with exit status 1
这显然是在使用 MinGW。
我也尝试在这里从轮子安装：
pip install https://pypi.python.org/packages/cp27/c/cffi/cffi-0.8.6-cp27-none-win32.whl#md5=aedc78351af65c4f514df0f2812473eb
我收到以下奇怪的错误：
Downloading/unpacking https://pypi.python.org/packages/cp27/c/cffi/cffi-0.8.6-cp27-none-win32.whl
Downloading cffi-0.8.6-cp27-none-win32.whl (77kB): 77kB downloaded
Running setup.py egg_info for package from https://pypi.python.org/packages/cp27/c/cffi/cffi-0.8.6-cp27-none-win32.whl
Traceback (most recent call last):
File "<string>", line 16, in <module>
IOError: [Errno 2] No such file or directory: 'c:\\users\\me\\appdata\\local\\temp\\pip-nkx4aq-build\\setup.py'
事实上，当我查看那个 (temp) pip-nkx4aq-build 目录时，我发现那里没有 setup.py。
所以，我的问题很简单，为什么会失败，我需要做什么才能在 Windows 上安装 cffi？