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

[Daniel J S. <dan...@ie...>]

Per Persson wrote:
> On Sep 28, 2006, at 21:21, gnu...@li...  
> wrote:
> 
> 
>>>there is no mention of a variable signgam.
>>
>>And that's a solid bug in any OS math library that purports to  
>>implement
>>C99 or any recent level of Unix standard compliance.  lgamma() is
>>required to be there, and it's equally required to have a signgam  
>>to go
>>with it.
> 
> 
> Mentioned or not, it is present in my ppc/math.h, and I think we have  
> shown it to be broken on Intel based Macs.

I'm not so certain we have shown that it is broken.  My point is that signgam has no relation to lgamma() anymore in the context of C99.  I'll make a guess that if you grep lgamma, the function doesn't reside in math.h.  It is in tgmath.h.

signgam probably is hanging around the header world because it is intendend for the legacy version of gamma() which used it.  So, if Chris were to try using the combination of gamma() with signgam (not the combination of lgamma() and signgam which is the prefered function as gnuplot is currently programmed) then that would be a bug.

In the patch I've removed the following:

#if defined(GAMMA) && !HAVE_DECL_SIGNGAM
extern int signgam;		/* this is not always declared in math.h */
#endif

Such a thing can only lead to problems if the idea is to be C99 compliant.

Dan