[petsc-dev] libm autodetection broken with -ffast-math

[Jed Brown]

Satish Balay <balay at mcs.anl.gov> writes:
> There are compilers that automatically link with internal libm
> equivalent - so absense of '-lm' is a valid usage. And then there are
> compielers that have -lsunpro or -lsci for such things..

Hmm, and perhaps passing -lm would be harmful because it would get an
abysmal reference implementation put in place so that only "experts" can
have fast code?

> And there are compilers that use '/usr/lib/libm.a' and not -lm :(

This is not so much of a problem unless -lm silently succeeds.  I'd
rather have a sensible error message on irrational systems than a
confusing late error on rational systems.
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