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List:       gcc-fortran
Subject:    Re: [PATCH] fortran, libgfortran, v2: Avoid using libquadmath for glibc 2.26+
From:       Joseph Myers <joseph () codesourcery ! com>
Date:       2022-06-27 20:54:32
Message-ID: alpine.DEB.2.22.394.2206272049320.211537 () digraph ! polyomino ! org ! uk
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On Mon, 27 Jun 2022, Jakub Jelinek via Gcc-patches wrote:

> On Sun, Jun 26, 2022 at 08:45:28PM +0200, Mikael Morin wrote:
> > I don't like the _Float128 vs __float128 business, it's confusing.
> > And accordinog to https://gcc.gnu.org/onlinedocs/gcc/Floating-Types.html
> > they seem to be basically the same thing, so it's also redundant.
> 
> I thought __float128 and _Float128 are distinct and incompatible in the FEs
> and equivalent in middle-end and back-end, but apparently they are
> considered equivalent even for _Generic.

Yes, when both are supported, they are the same type.  The main 
differences (not relevant for this patch, I think) are:

* _Float128 is supported on systems where long double has the IEEE 
binary128 format (as a distinct type from long double even when they have 
the same format); __float128 generally isn't supported on such systems.

* __float128 is supported in C++, _Float128 isn't (though we've discussed 
adding support for _FloatN type names and corresponding fN constant 
suffixes in C++; see the thread on the gcc list in March 2021).

-- 
Joseph S. Myers
joseph@codesourcery.com
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