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Re: [PATCH] PR libstdc++/84654 Do not use __float128 if it is disabled by the compiler
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Tulio Magno Quites Machado Filho <tuliom at linux dot vnet dot ibm dot com>, Michael Meissner <meissner at linux dot vnet dot ibm dot com>
- Cc: libstdc++ at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org, wschmidt at linux dot vnet dot ibm dot com, segher at kernel dot crashing dot org
- Date: Thu, 1 Mar 2018 20:10:03 +0100
- Subject: Re: [PATCH] PR libstdc++/84654 Do not use __float128 if it is disabled by the compiler
- Authentication-results: sourceware.org; auth=none
- References: <20180301184719.16691-1-tuliom@linux.vnet.ibm.com>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Thu, Mar 01, 2018 at 03:47:19PM -0300, Tulio Magno Quites Machado Filho wrote:
> In order to use the __float128 in C++ it's necessary to check if
> it is supported in libstdc++ (i.e. via _GLIBCXX_USE_FLOAT128) and if the
> compiler enabled its support too, e.g. -mfloat128 or -mno-float128.
>
> 2018-03-01 Tulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com>
Two spaces between date and name and name and email address.
> PR libstdc++/84654
> * include/bits/std_abs.h: Avoid to use __float128 when the
> compiler disabled it.
> * include/std/type_traits: Likewise.
That is incorrect. Only powerpc* defines __FLOAT128__ macro, but it isn't
the only one with __float128 type, e.g. x86_64-linux provides __float128
too, but doesn't define __FLOAT128__.
On x86_64-linux one can check for defined(__SIZEOF_FLOAT128__) instead.
One could argue that what powerpc does is wrong, defining __SIZEOF_*__ is
consistent with all the other __SIZEOF_*__ macros.
Also (up to libstdc++ maintainers) I'd say that _GLIBCXX_USE_FLOAT128
macro should depend on this macro, rather than uglifying all the uses.
So, #undef somewhere _GLIBCXX_USE_FLOAT128 if __SIZEOF_FLOAT128__ is
not defined.
Jakub