Re: [PATCH v2] Handle private COMDAT function symbol reference in readonly data section

[Jakub Jelinek <jakub@redhat.com>]

On Wed, Jan 31, 2024 at 08:48:33AM -0800, H.J. Lu wrote:
> Which function (target hook) can I use to generate
> 
>  .section        .data.rel.ro.local,"awG",@progbits,_ZN1AIxE3fooExx,comdat

Just
      if (decl)
	return get_section (reloc == 1
			    ? ".data.rel.ro.local" : ".data.rel.ro",
			    SECTION_WRITE | SECTION_RELRO | SECTION_LINKONCE,
			    decl);
for the first hunk and
  else if (decl)
    return get_section (".rodata", SECTION_LINKONCE, decl);
in the second case?

Haven't tried it though, maybe the get_section section conflict stuff
isn't able to handle it (and perhaps that is the reason why we simply don't
emit functions into
	.section	.text,"axG",@progbits,whatever,comdat
sections instead of
	.section	.text.function_name,"axG",@progbits,whatever,comdat
In such case, we could append something to those section names,
like const.pool (or whatever else that couldn't clash with function names,
so needs probably a dot somewhere).  Could be
.data.rel.ro.local.const.pool
.data.rel.ro.const.pool
or
.data.rel.ro.local..shared
.data.rel.ro..shared
or something similar, but .data.rel.ro.local.shared would not be ok,
because it could clash with .data.rel.ro.local section for shared function.
    
> > Another question is if we need to do anything about the
> > DECL_COMDAT_GROUP (decl) && DECL_SECTION_NAME (decl)
> > && startswith (DECL_SECTION_NAME (decl), ".gnu.linkonce.t.")
> > case (older linkers) (i.e. when using years old GNU linkers).
> >
> 
> Should we support such targets? It is not easy for me to test it.

Perhaps let's wait if somebody files an issue with such configuration.

	Jakub