Re: [build] Fix Solaris gty handling (PR target/84379)

[Eric Botcazou <ebotcazou at adacore dot com>]

> As described in the PR, there are a couple of jit testsuite failures on
> Solaris when using /bin/as.  The errors point to GC issues and indeed,
> gcc/config/sol2.c lacked GTY markup.  This patch fixes that, following
> what darwin.c does for machopic_indirections.  I confess I have no idea
> why I had to change the code the way I did except for the fact that it
> works.  While formally I don't need approval, it would be nice if
> someone in the know could have a look.

The net effect of the patch is to block GC for the DECLs registered by calls 
to solaris_elf_asm_comdat_section, that is to say, the mere fact of passing 
these DECLs to the function ensures that they will be kept.

This obviously fixes the GC failures described in PR jit/84288.  However, this 
also means that, even if the DECLs could otherwise be collected, they won't be 
anymore once they are passed to solaris_elf_asm_comdat_section.

This may be the expected behavior or may be deemed good enough.  However, you 
may want to implement a cache-like behavior instead, where the DECLs passed to 
solaris_elf_asm_comdat_section are not automatically kept, but instead only 
the slots of the hash table are kept if their associated DECL is.  See the 
documentation of ggc_cache_remove in hash-table.h for further details.

-- 
Eric Botcazou