[PATCH 7/8] PR ld/24600: BFD: Add general linker support for mapless archives

[Hans-Peter Nilsson]

> Date: Sat, 27 Sep 2025 00:53:45 +0100
> From: "Maciej W. Rozycki" <macro@orcam.me.uk>

> Expand linker mapless archive support from XCOFF targets only across the 
> remaining ones.  For this tranform BFD code used by AR to produce symbol 
> maps to archive files such as to have a handler supplied to either write 
> a map to a file or convert symbol data to an archive symbol definition 
> table attached to an archive BFD as if read from a symbol map, but using 
> pointers to member BFDs rather than file offsets.  Retain XCOFF handling 
> code as it is.
> 
> Update documentation and adjust test cases accordingly now that mapless 
> archives are accepted for link by all targets.
> 
> This, notably, has triggered test failures:
> 
> cris-elf  +FAIL: Regular archive w/o index link
> cris-elf  +FAIL: Thin archive w/o index link
> crisv32-linux  +FAIL: Regular archive w/o index link
> crisv32-linux  +FAIL: Thin archive w/o index link
> 
> all caused by a segfault in `aout_get_external_symbols' trying to access 
> `aout_data' data of an ELF BFD.
> 
> This comes from a combination of factors.  Firstly, ELF and Linux CRIS 
> targets set the default BFD target to a.out and at the same time they 
> set the default linker emulation to ELF.  Secondly, for mapless archives 
> code in `bfd_check_format_matches' ignores the BFD target supplied by 
> the linker and resorts to iterating over all the BFD formats to find one 
> to match.  Thirdly, when called in the linker `bfd_generic_archive_p' 
> accepts any archive file without any verification of its member files.  
> Consequently the default a.out BFD target is chosen for ELF input.
> 
> This only affects the new feature and is not a regression, so shouldn't 
> stop this change and will best be sorted independently.

I can read the above as you're suggesting this patch,
despite it causing a regression in test results for cris-elf
and crisv32-linux, and still say it is "not a regression"?

I hope I misunderstood.  Perhaps those are new tests ("git
grep" doesn't hit).  Then please xfail them for cris*-elf
and cris*-linux.  I don't think we use kfail, that seems
more gdb?

I'm open to other changes that don't cause testsuite
regressions, like to the effect of not defaulting to a.out.
I don't remember that one, but it sounds wrong.

brgds, H-P