Re: LDBL_EQ_DBL Multilib Issues

[Joel Sherrill <joel@rtems.org>]

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On Tue, Sep 26, 2023 at 5:40 PM Jeff Johnston <jjohnstn@redhat.com> wrote:

> Have you thought about adding a special case in sys/config.h which
> when it has the appropriate conditions (platform plus compiler flag) will
> define/redefine _LDBL_EQ_DBL?
>
> It gets included as part of _ansi.h and after newlib.h.
>

Thanks! You are confirming it needs to be decided at build time and giving
me the location to move it to.

I will try to get a patch out as soon as I can.

Thanks.

--joel

>
> -- Jeff J.
>
>
> On Tue, Sep 26, 2023 at 10:43 AM Joel Sherrill <joel@rtems.org> wrote:
>
>> Hi
>>
>> I wondered when we reorganized LDBL_EQ_DBL logic if there wouldn't be a
>> multilib edge case. Chris encountered it.
>>
>> Attached is a simple test program based on the autoconf probe in
>> configure.ac that can be preprocessed with different CPU/ABI flags. The
>> following shows that the default on m68k is not the same as for the 5282.
>>
>> $ m68k-rtems6-gcc -O2 -E ldbl.c | less
>>
>> $ m68k-rtems6-gcc -O2 -E -mcpu=5282 ldbl.c | less
>>
>> Turns out the default flags end up with LDBL_EQ_DBL isn't defined but it
>> should be for -mcpu=5282 builds.
>>
>> I don't know any mechanism to add header file variants in newlib by
>> multilib, so I we need to consider moving this to a dynamic check.
>>
>> Any thoughts on where to move this?
>>
>