Re: GOLD handling of weak symbols (including x86 vs. ARM)

[Cary Coutant <ccoutant at google dot com>]

> ===================================================================
> --- gold/i386.cc ? ? ? ?2010-11-09 08:21:13.000000000 +0000
> +++ gold/i386.cc ? ? ? ?2010-11-09 08:21:23.000000000 +0000
> -// Return whether we need to make a PLT entry for a relocation of a
> -// given type against a STT_GNU_IFUNC symbol.
> +// Get the Reference_flags for a particular relocation.
>
> -bool
> -Target_i386::Scan::reloc_needs_plt_for_ifunc(Sized_relobj<32, false>* object,
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?unsigned int r_type)
> +int
> +Target_i386::Scan::get_reference_flags(unsigned int r_type)
> ?{
> ? switch (r_type)
> ? ? {
> ? ? case elfcpp::R_386_NONE:
> ? ? case elfcpp::R_386_GNU_VTINHERIT:
> ? ? case elfcpp::R_386_GNU_VTENTRY:
> - ? ? ?return false;
> + ? ?case elfcpp::R_386_GOTPC:
> + ? ? ?// No symbol reference.
> + ? ? ?return 0;

> +// Return whether we need to make a PLT entry for a relocation of a
> +// given type against a STT_GNU_IFUNC symbol.
> +
> +bool
> +Target_i386::Scan::reloc_needs_plt_for_ifunc(Sized_relobj<32, false>* object,
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?unsigned int r_type)
> +{
> + ?int flags = get_reference_flags(r_type);
> + ?if (flags & Symbol::TLS_REF)
> + ? ?gold_error(_("%s: unsupported TLS reloc %u for IFUNC symbol"),
> + ? ? ? ? ? ? ? object->name().c_str(), r_type);
> + ?return flags != 0;
> +}

It looks like reloc_needs_plt_for_ifunc will now return a different
answer for R_386_GOTPC than it did before. Was that a bug before?

This function could probably use a comment explaining why (flags != 0)
is the right answer.

-cary