filter unwated cflags? (-ffast-math)

Michael Pyne mpyne at
Wed Apr 17 02:47:36 BST 2013

On Tue, April 16, 2013 20:29:25 Albert Astals Cid wrote:
> El Dimarts, 16 d'abril de 2013, a les 16:39:32, Bernd Buschinski va 
> > hi,
> Hi
> > I am not sure how do deal with unwanted cflags(cxxflags), so I ask here :)
> > 
> > For kjs for example -ffast-math is known to cause problems, as we stricly
> > rely on IEEE compatible floating point, NaN, Inf, signed Zero and all the
> > stuff.
> > 
> > So the question should I filter them? or leave it to the user to
> > optimize(break) his system?
> Well, if you know it'll break, you should shout. If that shouting means just
> a huge message or stopping the compilation i am not sure, but if it'll give
> you extra work for no reason in forme of bugs, etc. i'd go for stopping the
> compilation.

Having run into this before, I can only +1 this about 1000 times or so. KJS 
with -ffast-math and friends is unsupportable so there's no reason to let the 
compile go on if we can detect it. That code should be considered completely 
miscompiled, if a user wants to use the flag anyways they can take it on 
themselves to figure out CMake in addition.

 - Michael Pyne
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