Cython compilation errors: '-mno-fused-madd

Question

Whenever I compile Cython code (using pyximport) and frequently when I install packages from source (with pip) I get

clang: warning: argument unused during compilation: '-mno-fused-madd'

What is this warning and what can I do to prevent it? I suspect I may not be able to prevent when pip triggers it, but is thre at least some way to configure pyximport to avoid it?

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OS X 10.9, Python 2.7.5, Xcode clang 500.2.79

Answer 1

-mno-fused-madd is a gcc cpu target option. It is for enabling/disabling the generation of the fused multiply/add instructions (FMACs. Common in DSPs).

Since this is gcc-specific, clang gives a warning that it doesn't understand the option.

If you really don't want to see this warning you could try setting the default compiler by

env CC=/usr/bin/gcc pip install ...

This should also work for pyximport too (But I haven't tried).

Answer 2

The answer before didn't work for me, but it worked this to tell clang to ignore these error messages:

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

Solution found in clang error: unknown argument: '-mno-fused-madd' (python package installation failure)