Re: Changes to stable-5-0 branch

[Bastian M. <bma...@we...>]

Am 13.02.2016 um 21:23 schrieb sfeam:
(snip)
> In particular the change below is problematic because it was already tried in
> the main branch and turned out to cause problems on some systems:
>
>          * src/qtterminal/qt_term.h src/qtterminal/qt_conversion.cpp:  isnan()
>          is in namespace std.
>
> See 5.1 ChangeLog:
>
> 2015-12-10  Hans-Bernhard Broeker  <br...@ph...>
>
>          * src/qtterminal/qt_conversion.cpp (qt_imageToQImage): Do not call
>          C++ isnan() without a namespace specifier.
>
>          EAM:  Reverting this change.  We may need a fix, but this isn't it.
>          qtterminal/qt_conversion.cpp:
>          In function 'QImage qt_imageToQImage(int, int, coordval*, t_imagecolor)':
>          qtterminal/qt_conversion.cpp:129:14:
>          error: expected unqualified-id before '(' token if (std::isnan(*image))
>
> I don't know what the issue is here, but since adding the std:: qualifier
> is known to break the build on some systems that were perfectly happy before
> this, I think it is not suitable for the stable branch.
>

OK. Reverted in branch-5-0-stable.

The problem is that isnan is in the C99 standard, but wasn't in the C++ 
standard until C++11. Hence, many C++ compilers implemented it "their" 
way, as _isnan (MSVC), ::isnan, std::isnan or macro (as in C99). See 
e.g. the discussion at
http://stackoverflow.com/questions/570669/checking-if-a-double-or-float-is-nan-in-c
Btw. simply adding a "using namespace std" doesn't solve the issue 
either, since some compilers have both, ::isnan and std::isnan.

Too me it looks like the only way of solving this in a portable way is 
to implement a C function like this in e.g. stdfn.c|h :

TBOOLEAN gp_isnan(double v)
{
	return isnan(v);
}


   Bastian