在OS X上用pip安装bcrypt时出错：找不到ffi.h（libffi已安装）

Question

我在用pip安装bcrypt的时候遇到了这个错误。我在几个地方安装了libffi（比如Xcode的OS X SDK，还有通过homebrew安装的），但我不知道怎么让pip去找到它。有没有什么建议？

Downloading/unpacking bcrypt==1.0.2 (from -r requirements.txt (line 41))
  Running setup.py egg_info for package bcrypt
    OS/X: confusion between 'cc' versus 'gcc' (see issue 123)
    will not use '__thread' in the C code
    c/_cffi_backend.c:14:10: fatal error: 'ffi.h' file not found
    #include <ffi.h>
             ^
    1 error generated.
    Traceback (most recent call last):
      File "<string>", line 16, in <module>
      File "/Users/cody/virtualenvs/analytics/build/bcrypt/setup.py", line 104, in <module>
        "Programming Language :: Python :: 3.3",
      File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/distutils/core.py", line 112, in setup
        _setup_distribution = dist = klass(attrs)
      File "build/bdist.macosx-10.9-intel/egg/setuptools/dist.py", line 239, in __init__
      File "build/bdist.macosx-10.9-intel/egg/setuptools/dist.py", line 264, in fetch_build_eggs
      File "build/bdist.macosx-10.9-intel/egg/pkg_resources.py", line 620, in resolve
        dist = best[req.key] = env.best_match(req, ws, installer)
      File "build/bdist.macosx-10.9-intel/egg/pkg_resources.py", line 858, in best_match
        return self.obtain(req, installer) # try and download/install
      File "build/bdist.macosx-10.9-intel/egg/pkg_resources.py", line 870, in obtain
        return installer(requirement)
      File "build/bdist.macosx-10.9-intel/egg/setuptools/dist.py", line 314, in fetch_build_egg
      File "build/bdist.macosx-10.9-intel/egg/setuptools/command/easy_install.py", line 593, in easy_install

      File "build/bdist.macosx-10.9-intel/egg/setuptools/command/easy_install.py", line 623, in install_item

      File "build/bdist.macosx-10.9-intel/egg/setuptools/command/easy_install.py", line 811, in install_eggs

      File "build/bdist.macosx-10.9-intel/egg/setuptools/command/easy_install.py", line 1017, in build_and_install

      File "build/bdist.macosx-10.9-intel/egg/setuptools/command/easy_install.py", line 1005, in run_setup

    distutils.errors.DistutilsError: Setup script exited with error: command 'cc' failed with exit status 1
    Complete output from command python setup.py egg_info:
    OS/X: confusion between 'cc' versus 'gcc' (see issue 123)

will not use '__thread' in the C code

c/_cffi_backend.c:14:10: fatal error: 'ffi.h' file not found

#include <ffi.h>

         ^

1 error generated.

Traceback (most recent call last):

  File "<string>", line 16, in <module>

  File "/Users/cody/virtualenvs/analytics/build/bcrypt/setup.py", line 104, in <module>

    "Programming Language :: Python :: 3.3",

  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/distutils/core.py", line 112, in setup

    _setup_distribution = dist = klass(attrs)

  File "build/bdist.macosx-10.9-intel/egg/setuptools/dist.py", line 239, in __init__

  File "build/bdist.macosx-10.9-intel/egg/setuptools/dist.py", line 264, in fetch_build_eggs

  File "build/bdist.macosx-10.9-intel/egg/pkg_resources.py", line 620, in resolve

    dist = best[req.key] = env.best_match(req, ws, installer)

  File "build/bdist.macosx-10.9-intel/egg/pkg_resources.py", line 858, in best_match

    return self.obtain(req, installer) # try and download/install

  File "build/bdist.macosx-10.9-intel/egg/pkg_resources.py", line 870, in obtain

    return installer(requirement)

  File "build/bdist.macosx-10.9-intel/egg/setuptools/dist.py", line 314, in fetch_build_egg

  File "build/bdist.macosx-10.9-intel/egg/setuptools/command/easy_install.py", line 593, in easy_install



  File "build/bdist.macosx-10.9-intel/egg/setuptools/command/easy_install.py", line 623, in install_item



  File "build/bdist.macosx-10.9-intel/egg/setuptools/command/easy_install.py", line 811, in install_eggs



  File "build/bdist.macosx-10.9-intel/egg/setuptools/command/easy_install.py", line 1017, in build_and_install



  File "build/bdist.macosx-10.9-intel/egg/setuptools/command/easy_install.py", line 1005, in run_setup



distutils.errors.DistutilsError: Setup script exited with error: command 'cc' failed with exit status 1

----------------------------------------
Command python setup.py egg_info failed with error code 1 in /Users/cody/virtualenvs/analytics/build/bcrypt

Answer 1

更新于2015年8月26日

我觉得TA的回答更好，因为这是系统处理的。

---

首先，我不太想安装Brew或Ports，不过那是另一个话题。

我一直在尝试用 pip install cryptography 来安装一个叫做cryptography的库，它依赖于cffi，而cffi又需要引入 ffi.h。

我很好奇为什么没有人提到他（还有我，以及我相信其他人）在Xcode中已经安装了 ffi：

locate ffi.h
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/usr/include/ffi/ffi.h

因为错误信息特别提到“找不到” ffi.h，而且用的是以下的构建命令：

c/_cffi_backend.c:14:10: fatal error: 'ffi.h' file not found
#include <ffi.h>
...
...
/usr/bin/clang ...{omitted}... I/usr/include/ffi -I/usr/include/libffi

我确实有 ffi.h，只是系统认为它应该在 /usr/include/... 这个地方。

我的 /usr/include 目录恰好是空的，也没有链接到任何东西，所以我就把这个文件/目录链接到了它找不到的地方：

ln -fs {THAT_XCODE_SDK_FFI_PATH_FROM_ABOVE} /usr/include/ffi

现在我可以安装和构建cffi和cryptography了。

我对理解构建链和链接的动态过程非常菜，如果这样做不好，我也不太明白……所以，请告诉我。

Answer 2

Xcode已经为我安装好了（正如问题中提到的，它确实提供了ffi.h这个头文件），但是不知道为什么它没有把文件放到/usr/include这个目录下（正如Zachary Young提到的）。我查了一下为什么/usr/include没有被填充，发现下面这个命令可以解决这个问题：

$ xcode-select --install

在Yosemite和Xcode安装后，/usr/include缺失？

Answer 3

我终于在一些帮助下搞定了这个问题，具体是参考了这些和帖子：

brew install pkg-config libffi
sudo bash
export CFLAGS=-Qunused-arguments
export CPPFLAGS=-Qunused-arguments
export PKG_CONFIG_PATH=/usr/local/Cellar/libffi/3.0.13/lib/pkgconfig/
pip install bcrypt

Answer 4

不使用sudo，也不需要CFLAGS和CPPFLAGS（对于pip来说这些都是多余的）：

$ brew install pkg-config libffi
$ export PKG_CONFIG_PATH=/usr/local/Cellar/libffi/3.0.13/lib/pkgconfig/
$ pip install bcrypt