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[PATCH] gas: Fix -mrelax-relocations detection on Solaris/x86 [PR19520]

Rainer Orth ro@CeBiTec.Uni-Bielefeld.DE
Sun Oct 12 12:29:17 GMT 2025 
Hi Jan,

> On 28.09.2025 16:16, Rainer Orth wrote:
>> I recently noticed a complex case statement in gas/configure.ac controlling
>> the setting of ac_default_x86_relax_relocations on Solaris/x86.  Since it
>> included all versions of Solaris, it could be massively simplified.
>> 
>> Looking closer however, I found that it was introduced in
>> 
>> commit 0cb4071ef9e10f703220f5e731141bf438aca16e
>> Author: H.J. Lu <hjl.tools@gmail.com>
>> Date:   Wed Feb 3 08:25:15 2016 -0800
>> 
>>     Add -mrelax-relocations= to x86 assembler
>> 
>> based on PR gas/19520.  This PR reported that the new R_386_GOT32X
>> etc. relocations weren't supported on older versions of Solaris,
>> breaking gcc bootstrap.  In response, they were disabled on all Solaris
>> versions except Solaris 12, where they had been implemented in the
>> native toolchain based on my findings.
>> 
>> However, Solaris 12 has been rechristened to 11.4 before release,
>> effectively disabling DEFAULT_GENERATE_X86_RELAX_RELOCATIONS on all
>> versions of Solaris/x86.
>> 
>> This patch fixes this by correcting the detection of Solaris 11.4.  Since
>> the minor version is not included in the configure triplet, this can only
>> be done natively with uname -v.
>> 
>> Tested on i386-pc-solaris2.11 and amd64-pc-solaris2.11 (Solaris 11.4)
>> and with gcc trunk bootstraps with the patched gas and native ld.  Also
>> tested on Solaris 11.3/x86 (build only to check that the macro is set to
>> 0 as expected).
>> 
>> Ok for trunk?
>
> Hmm, no, not really. What target an assembler is built for shouldn't
> really depend on host properties imo. There's no other similar use
> of uname anywhere in the script.

what else could I do?  Natively, I see three options:

* Try to link an object containing one of the gotx relocs with /bin/ld.
  However, that might be difficult to create since there's no guarantee
  that gas is even available when building binutils.

* Check the native <sys/elf_i386.h> and <sys/elf_amd64.h> if the gotx
  relocs are defined there.

* Check if the exact OS version is 11.4.

None of this works for crosses:

* The first is obviously impossible.

* The second would work, but the natively headers are most likely not
  available for a cross build.

* The third won't work either since the info about the minor OS versions
  isn't included in the target triplet.

That's why I used the uname route in the native case while erring on the
side of caution for crosses by disabling gotx reloc support.

If you have other suggestions, I'm all ears.

	Rainer

-- 
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Rainer Orth, Center for Biotechnology, Bielefeld University
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