Re: [PATCH, Fortran] Revert to non-multilib-specific ISO_Fortran_binding.h

[Jakub Jelinek <jakub@redhat.com>]

On Mon, Sep 13, 2021 at 06:32:56PM +0200, Tobias Burnus wrote:
> On 13.09.21 17:56, Gerald Pfeifer wrote:
> > This broke bootstrap on i586-unknown-freebsd11:
> > 
> >    In file included from .../GCC-HEAD/libgfortran/runtime/ISO_Fortran_binding.c:30:
> >    .../GCC-HEAD/libgfortran/ISO_Fortran_binding.h:255:2:
> >    error: #error "Can't determine kind of long double"
> >    255 | #error "Can't determine kind of long double"
> >        |  ^~~~~
> > 
> > Does this work on i586-*-linux?
> > 
> > 
> > % egrep -r '#define.*LDBL_(MANT_DIG|MIN_EXP|MAX_EXP)' /usr/include/
> > /usr/include/x86/float.h:#define LDBL_MANT_DIG  64
> > /usr/include/x86/float.h:#define LDBL_MIN_EXP   (-16381)
> > /usr/include/x86/float.h:#define LDBL_MAX_EXP   16384
> > 
> > This looks like it matches existing Linux case already in place?
> 
> Can you run 'echo | cpp -E -g3|grep DBL' to (or in the build dir: echo |
> ./gcc/cc1 -E -g3 -dD|grep DBL) to check what's the output?
> 
> It might be that /usr/include/x86/float.h is not used; e.g. there is
> $(gcc-src)/ginclude/float.h which undef's the LDBL_MAX_EXP to replace it
> by a #define using __LDBL_MAX_EXP. Thus, if those are different from the
> values under /usr/include, it might be the reason for the fail?
> 
> I think it works under Linux, at least the "x86-64 -m32"
> libgfortran.{so,a}  build and the -m32 testsuite runs do work.

Wouldn't it be better to use the __LDBL_* macros anyway and not rely on
float.h?  The header doesn't want to test what float.h tells about the
long double type, but what the compiler knows about it.

	Jakub