Re: ppc64le: gcc 12 vs -mabi=ibmlongdouble

[Bill Schmidt <wschmidt@linux.ibm.com>]

I ran this by our GCC team, and the tentative consensus is that 
-mlong-double-64 should override -mabi=ibmlongdouble, rather than 
reporting an error in the compile flags.  DJ, could you please
open a bug against the GCC powerpc target?

Thanks!
Bill

On 1/24/22 9:38 AM, Florian Weimer via Libc-alpha wrote:
> * DJ Delorie via Libc-alpha:
>
>> I've been working on updating glibc for Fedora Rawhide, and have
>> stumbled upon this issue (after working around the -Wuse-after-free
>> issues with a cflags hack)...  A few of the math tests explicitly add
>> -mlong-double-64 but configure adds -mabi=ibmlongdouble
>>
>> I would guess that we need a "CFLAGS -= -mabi=ibmlongdouble" in all
>> the places we add -mlong-double-64 but I don't see an easy way of
>> doing that, nor am I sure that's a valid solution.  Alternately, gcc
>> could be changed to accept the conflicting flags in a meaningful way,
>> if there is one.  Is there an -mabi= that undoes the
>> -mabi=ibmlongdouble that we can just add to the -mlong-double-64 flag
>> lines?
>> cc1: error: '-mabi=ibmlongdouble' requires '-mlong-double-128'
> I was able to reproduce with a GCC 12 build configured using
> --with-long-double-format=ieee.
>
> I tried the attached patch to remove the unwanted -mabi=ibmlongdouble,
> but it does not work: it removes CFLAGS-*.c processing as a side effect.
>
> Any suggestions how we can fix this properly?
>
> Thanks,
> Florian