Error installing bcrypt with pip on OS X: can't find ffi.h (libffi is installed)

Question

I\'m getting this error when trying to install bcrypt with pip. I have libffi installed in a couple places (the Xcode OS X SDK, and from homebrew), but I don\'t know how to

Answer 1

Update 26/Aug/15

I think TA's answer is better in that it's handled by the system.

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First off, I'm loathe to install Brew or Ports, but that's another issue.

I've been trying to pip install cryptography, which depends on cffi, which imports ffi.h.

I am curious why no one addressed that he (and me, and I believe others) have ffi installed with Xcode:

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

since the error is specifically about "not finding" ffi.h with the following build command:

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

I have ffi.h, it's just that the system thinks it should be in /usr/include/....

My /usr/include directory happens to be empty, and not linked to anything, so I just linked the directory/file in question, to the place where it's not being found:

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

I can now install and build cffi and cryptography.

I'm very novice when it comes to understanding build-chain/linking dynamics, and if this is bad, I don't get it... so, please let me know.