Improve the patch for NaN with MSVC

[seisman]

Description of proposed changes

Not sure what's happening. Changes in PR #8627 passed in that PR, but failed after merging into the master branch (see https://github.com/GenericMappingTools/gmt/actions/runs/11934957233/job/33265224118).

ChatGPT told me:

In C, a static const variable at global scope must be initialized with a constant expression that can be evaluated at compile time. However:

(1e+300 * 1e+300) * 0.0F involves floating-point arithmetic, which is not considered a compile-time constant in most C compilers.

HUGE_VAL - HUGE_VAL is also not a compile-time constant for the same reason.

So, this PR improves the definition NAN without any floating-point arithmetic.

With the new patch, the conda-forge building in conda-forge/gmt-feedstock#302 passes.

[seisman]

Hmmm, the patch still doesn't work in our CI.

[joa-quim]

The definition I found in another Windows Kits header was
#define NAN (-(float)(INFINITY * 0.0F))
where
#define INFINITY ((float)(_HUGE_ENUF * _HUGE_ENUF))
and

#ifndef _HUGE_ENUF
#define _HUGE_ENUF 1e+300 // _HUGE_ENUF*_HUGE_ENUF must overflow
#endif

My first attempt had just (no const qualifier)

#define NAN (-(float)(1e+300 * 1e+300 * 0.0F))

and that passed our CI'

Edit: I see that your change was to put it like that, but you also changed the non MSVC branch. Better not do it. If the problem is only with MSVC, restrict changes to it.

EDIT2: The other difference to my first patch is that it was applied into a different header, that presumably was included first that this one.

[seisman]

Not sure what's happening. Changes in PR #8627 passed in that PR, but failed after merging into the master branch (see https://github.com/GenericMappingTools/gmt/actions/runs/11934957233/job/33265224118).

it turns our in PR #8627, the CI was still using the old MSVC 19.41.34123.0 (that's why the CI passes), while in the master branch and this PR, the CI has upgraded to MSVC 19.42.34433.0.

[joa-quim]

OK, let's try this that is a distillation of the NAN definition in a header called corecrt_math.h

#ifndef NAN
#	ifndef INFINITY
#		ifndef _HUGE_ENUF
#			define _HUGE_ENUF 1e+300 // _HUGE_ENUF*_HUGE_ENUF must overflow
#		endif
#		define INFINITY ((float)(_HUGE_ENUF * _HUGE_ENUF))
#	endif
#	define NAN (-(float)(INFINITY * 0.0F))
#endif

[seisman]

OK, let's try this that is a distillation of the NAN definition in a header called corecrt_math.h

can we just include this header file?

[joa-quim]

Sounds complicated. That header is part of Windows Kits, which I'm not even sure it belongs to MSVC (probably not).