meaning of supports_gnu_unique

[Alan Modra]

On Fri, Mar 27, 2026 at 08:42:33AM +0100, Jan Beulich wrote:
> On 27.03.2026 00:27, Alan Modra wrote:
> > On Thu, Mar 26, 2026 at 03:35:55PM +0100, Jan Beulich wrote:
> >> may I ask what the purpose is of this predicate used by the testsuite?
> >> By its name I would in particular expect it to cover the
> >> %gnu_unique_object symbol type (supported by the comment there), but as
> >> demonstrated by ld-unique/unique failing for arm-unknown-linux-gnu there
> >> must be something I'm missing.
> > 
> > I don't see any fails on my cross builds of arm-linux-gnueabi..
> 
> That one's fine indeed. The one I named (shorthand arm-linux) isn't.
> 
> > Maciej was the original author of that function.  I extracted out
> > supports_gnu_osabi, prior to which the comment for supports_gnu_unique
> > said:
> > 
> > # True if the ELF target supports STB_GNU_UNIQUE with the ELF header's
> > # OSABI field set to ELFOSABI_GNU.
> > #
> > # This generally depends on the target OS only, however there are a
> > # number of exceptions for bare metal targets as follows.  The MSP430
> > # and Visium targets set OSABI to ELFOSABI_STANDALONE and cannot
> > # support STB_GNU_UNIQUE.  Likewise non-EABI ARM targets set OSABI to
> > # ELFOSABI_ARM, and TI C6X targets to ELFOSABI_C6000_*.  Finally
> > # rather than `bfd_elf_final_link' a number of targets use
> > # `_bfd_generic_final_link', which does not support STB_GNU_UNIQUE
> > # symbol binding causing assertion failures.
> > #
> 
> The ELFOSABI_ARM aspect was even mentioned there (and still is in
> today's form of the comment). If the comment is correct, the
> *-*-gnu* pattern used in supports_gnu_osabi would need amending to
> exclude the target above. But: How can *-*-*gnu* not be a GNU target?
> What would the "gnu" in there indicate then?

I think you should view supports_gnu_unique and supports_gnu_osabi in
context as testsuite support, rather than as definitive for gnu
targets.  Yes, I agree that arm-linux-gnu should be excluded from
supports_gnu_osabi.

If you take a look at ld-unique/unique.exp you'll see tests that check
for readelf output of OSABI "UNIX GNU", ie. ELFOSABI_GNU.  Other
values of OSABI may well support the various gnu object file
extensions.

> Judging from the comments, I would have expected tic6x to have a
> similar issue, but I haven't observed such in practice. This looks to

Yes, tic6x is excluded from testing in ld-unique/unique.exp.

> be a result of the assembler only ever using (OSABI-generic) targets
> which bfd/config.bfd installs as secondary ones.
> 
> Jan

-- 
Alan Modra