Re: [PATCH] Gold: Implement the '--discard-locals' and '-X' options.

[Ian Lance Taylor <iant at google dot com>]

"Doug Kwan (éæå)" <dougkwan@google.com> writes:

>        const char* name = pnames + sym.get_st_name();
> +      if (discard_locals
> +	  && sym.get_st_type() != elfcpp::STT_FILE
> +	  && parameters->target().is_local_label_name(name))
> +	{
> +	  lv.set_no_output_symtab_entry();
> +          gold_assert(!lv.needs_output_dynsym_entry());
> +	  continue;
> +	}

Instead of asserting, don't discard the symbol if
lv.needs_output_dynsym_entry() returns true.

> +  // Virtual function which may be overriden by the child class.
> +  virtual bool
> +  do_is_local_label_name(const char* name) const
> +  {
> +    // The logic is the same as that in _bfd_elf_is_local_label_name().
> +   
> +    // Normal local symbols start with ``.L''.
> +    if (name[0] == '.' && name[1] == 'L')
> +      return true;
> +
> +    // At least some SVR4 compilers (e.g., UnixWare 2.1 cc) generate
> +    // DWARF debugging symbols starting with ``..''.
> +    if (name[0] == '.' && name[1] == '.')
> +      return true;
> +
> +    // gcc will sometimes generate symbols beginning with ``_.L_'' when
> +    // emitting DWARF debugging output.  I suspect this is actually a
> +    // small bug in gcc (it calls ASM_OUTPUT_LABEL when it should call
> +    // ASM_GENERATE_INTERNAL_LABEL, and this causes the leading
> +    // underscore to be emitted on some ELF targets).  For ease of use,
> +    // we treat such symbols as local.
> +    if (name[0] == '_' && name[1] == '.' && name[2] == 'L' && name[3] == '_')
> +      return true;
> +
> +    return false;
> +  }

This is too big to define inline in the class.  Define it in target.h
just below the class definition.  Add a target.cc file and define it
there.

> +# '-Wa,--keep-locals' is required to preserve the local label used for testing.
> +discard_locals_test.o: discard_locals_test.c
> +	$(COMPILE) -c -Wa,--keep-locals -o $@ $<

s/--keep-locals/-L/g

> +int
> +main (void)
> +{
> +  /* local symbol format for generic ELF target. */
> +  asm (".Lshould_be_discarded:");
> +
> +#ifdef __i386__
> +  /* additional local symbol format for the i386 target. */
> +  asm (".Xshould_be_discarded:");
> +#endif
> +
> +  return 0;
> +}

I think it would be better to put the asm statements outside of the main
function.

Please send another patch with these changes for final approval.

Thanks.

Ian