[Bug libfortran/66936] io/unix.c gratuitously uses S_IRWXG and S_IRWXO on the basis that umask() is available

["pinskia at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66936

--- Comment #9 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Keith Marshall from comment #8)
> (In reply to kargl from comment #7)
> > So add
> > 
> > #define S_IRWXG 0
> > #define S_IRWXO 0
> > 
> > to the header file wherever mingw defines the available mask bits
> > for umask(3).  The bug is clearly in mingw were it gratuitously maps
> > umask() to _umask() without properly adding the mappings for the
> > mode_t argument bits of umask(3).
> 
> Absolutely not!  Those bits are utterly irrelevant for the windows (MinGW)
> platform; to add them would be do nothing more than create confusion.  The
> mask bits for umask(), on the windows platform are S_IREAD | S_IWRITE; those
> are the only mask bits YOUR code should be passing to non-POSIX
> umask(5axxx3be.aspx).
> 
> This is NOT a MinGW bug; it's a GCC bug, and that's where it should be
> fixed.  Until you do fix it, I have my work-around, (which I'm perfectly
> willing to publish in MinGW forked source for GCC, prominently commented as
> a ghastly hack to circumvent a gross upstream GCC bug).


Well it is a libgfortran bug yes.  What we could do add to io/unix.c:
#if MINGW && !defined(S_IRWXG)
#define S_IRWXG 0
#endif
#if MINGW && !defined(S_IRWXO)
#define S_IRWXO 0
#endif

And that will allow it to work correctly.