Re: [Fwd: Re: gnuplot numerical errors on Intel MacBook]

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Daniel J Sebald wrote:

> There may be more to this.  I see now that "signgam" is actually an
> external as part of the math library I'm guessing.  

No need for guessing --- that's what you have libc/libm manpages for.

 > So, if I
> understand this, calling gamma() (i.e., the "old gamma" which is
> actually ln gamma) will set the sign of the gamma function upon
> calling gamma().  How is an optimizing compiler to know that?

It doesn't have to.  signgam is a global variable, exported by the 
library, and the code reads it.

> Anyway, maybe just avoiding the use of "signgam" in any way is best.

We can't do that.  Not on platforms that don't sport a tgamma(), anyway.