clang - "'cc' failed with exit status 1" error when install python library

Question

Like many others, I'm having issues installing a python library (downloaded as a tar, then extracted).

rodolphe-mbp:python-Levenshtein-0.11.2 Rodolphe$ sudo python setup.py install
running install
running bdist_egg
running egg_info
writing requirements to python_Levenshtein.egg-info/requires.txt
writing python_Levenshtein.egg-info/PKG-INFO
writing namespace_packages to python_Levenshtein.egg-info/namespace_packages.txt
writing top-level names to python_Levenshtein.egg-info/top_level.txt
writing dependency_links to python_Levenshtein.egg-info/dependency_links.txt
writing entry points to python_Levenshtein.egg-info/entry_points.txt
reading manifest file 'python_Levenshtein.egg-info/SOURCES.txt'
reading manifest template 'MANIFEST.in'
warning: no files found matching '*' under directory 'docs'
warning: no previously-included files matching '*pyc' found anywhere in distribution
warning: no previously-included files matching '.project' found anywhere in distribution
warning: no previously-included files matching '.pydevproject' found anywhere in distribution
writing manifest file 'python_Levenshtein.egg-info/SOURCES.txt'
installing library code to build/bdist.macosx-10.9-intel/egg
running install_lib
running build_ext
building 'Levenshtein' extension
cc -fno-strict-aliasing -fno-common -dynamic -arch x86_64 -arch i386 -g -Os -pipe -fno-common -fno-strict-aliasing -fwrapv -mno-fused-madd -DENABLE_DTRACE -DMACOSX -DNDEBUG -Wall -Wstrict-prototypes -Wshorten-64-to-32 -DNDEBUG -g -fwrapv -Os -Wall -Wstrict-prototypes -DENABLE_DTRACE -arch x86_64 -arch i386 -pipe -I/System/Library/Frameworks/Python.framework/Versions/2.7/include/python2.7 -c Levenshtein.c -o build/temp.macosx-10.9-intel-2.7/Levenshtein.o
clang: error: unknown argument: '-mno-fused-madd' [-Wunused-command-line-argument-hard-error-in-future]
clang: note: this will be a hard error (cannot be downgraded to a warning) in the future
error: command 'cc' failed with exit status 1

As suggested elsewhere, I tried entering in terminal "ARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future sudo python setup.py install", but no success.

Is there a way around this issue that seems to have appeared with xcode 5.1?

Answer 1

Run these two lines in your shell before you build:

export CFLAGS=-Qunused-arguments
export CPPFLAGS=-Qunused-arguments

Those exports tell the compiler to ignore unused arguments rather than complaining about them.

---

The reason seems to be that Python is compiling modules using the options that it was built with, except one of those options no longer works in mavericks:

the clang 3.4 Apple is shipping defaults to erroring on unknown flags, but CPython builds modules using the same set of flags it was compiled with originally.

(from: https://stackoverflow.com/a/22315129/65295)

Lots of people are running into this:

• Ansible Installation -clang: error: unknown argument: '-mno-fused-madd'
• Can't install python mysql library on Mac Mavericks
• clang error: unknown argument: '-mno-fused-madd' (python package installation failure)