[Fwd: Re: [PATCH 1 of 3] arch: s390 and 390x glibc patch]

[Mike Frysinger]

On Saturday 14 November 2009 19:36:44 Yann E. MORIN wrote:
> On Saturday 14 November 2009 17:28:26 Mike Frysinger wrote:
> > > > > Mike Frysinger wrote:
> > > > > >under Gentoo, a bunch of cache vars
> > > > > >are forced just for the headers step as there is no compiler to
> > > > > > test. those include mlong double tests.
> > > > > >	libc_cv_mlong_double_128=yes
> > > > > >	libc_cv_mlong_double_128ibm=yes
> >
> > these are settings that should always be there and the user shouldnt be
> > forced to configure themselves.  it also isnt specific to s390 ... it
> > comes up with ppc targets too.
> > for the headers step, it's safe to export these all the time for all
> > targets. we've been doing this in gentoo for quite a long time now.
> 
> You mean unconditionally? On my x86_64 machine, debian lenny:
> - in 64-bit mode: sizeof( long double ) = 16 bytes = 128 bits
> - in 32-bit mode: sizeof( long double ) = 12 bytes =  96 bits
> 
> So, does it really makes sense to _unconditionnally_ set long-double-128?
> The gcc man page says that on x86 (32-bit) the ABI specifies a size of
> 96 bits for long double.
> 
> Also, what does long-double-128ibm means?

i mean what i said.  if you read the glibc configure script, you'll see these 
are simply toolchain sanity checks.  they dont affect header generation in any 
way.  the sizeof long double is also irrelevant -- which you'll see when you 
read the configure scripts.
-mike
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