[Patch, Fortran] PR39505 - add support for !GCC$ attributes NO_ARG_CHECK

[Tobias Burnus]

Thomas Koenig wrote:
>> Is my -f(no-)directives patch okay? Or do you envision something else?
>
> In principle, it is OK; the only question is what the default should 
> be :-)

I am in favor of "on".

> For OpenMP, we require an option to change the semantics of a program
> based on special comments.  Currently, we do not do so for directives
> which do the same thing.

Well, I see a difference here: (Nearly) all program using OpenMP work 
also as serial program (-fno-openmp). On the other hand, without "!GCC$ 
attributes" directives (or the C equivalent: "__attribute__((...))"), 
the program does not work properly. The attributes are used to be able 
to express some feature which is not available in the standard but still 
in some way required: stdcall, fastcall, dllimport, dllexport. "unused" 
arguments, weak bindings (not yet for Fortran), disabling argument 
checking (only Fortran), etc.

Tobias