[Bug gold/16693] "exclude-libs" drops symbols that are exported through "dynamic-list" or "export-dynamic-symbol"

[ostap73 at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16693

--- Comment #4 from Viatcheslav Ostapenko <ostap73 at gmail dot com> ---
(In reply to H.J. Lu from comment #3)
> (In reply to Viatcheslav Ostapenko from comment #2)
> > Created attachment 7465 [details]
> > Test
> > 
> > Attached test miniproject.
> > 
> > In resulting test.so dynamic_list_exported_from_static_lib() should be
> > exported by dynamic list, but is missing from exports.
> > 
> 
> --dynamic-list isn't used to control which symbols are exported or
> not.  From ld manual:
> 
> '--dynamic-list=DYNAMIC-LIST-FILE'
>      Specify the name of a dynamic list file to the linker.  This is
>      typically used when creating shared libraries to specify a list of
>      global symbols whose references shouldn't be bound to the
>      definition within the shared library, or creating dynamically
>      linked executables to specify a list of symbols which should be
>      added to the symbol table in the executable.  This option is only
>      meaningful on ELF platforms which support shared libraries.

That's very strange!
>From code in symtab.cc (should_add_dynsym_entry):

  // If the symbol was forced dynamic in a --dynamic-list file
  // or an --export-dynamic-symbol option, add it.
  if (!this->is_from_dynobj()
      && (parameters->options().in_dynamic_list(this->name())
    || parameters->options().is_export_dynamic_symbol(this->name())))
    {
      if (!this->is_forced_local())
        return true;
      gold_warning(_("Cannot export local symbol '%s'"),
        this->demangled_name().c_str());
      return false;
    }

At least from code here it seems dynamic-list option does the same as
export-dynamic-symbol option, but not for the single symbol, but for the list
or pattern specified in file.
I see clear use case for this when developer chooses to specify exports in a
single file.

> If you remove/change --dynamic-list, you will get the same set of
> symbols in dynamic symbol table.  Please tell us exactly what you
> want to see in test.so.

Sorry, I forgot to specify default visibility for symbols.
Tried it now and got into another problem.
If I specify default visibility then I get warnings:
ld.gold: warning: Cannot export local symbol 'dynamic_list_exported_directly'
ld.gold: warning: Cannot export local symbol
'dynamic_list_exported_from_static_lib'

And those functions are not exported.
It is the same code piece I've pasted above and you can see that it hits
is_forced_local() local condition. Function force_local is called on condition:

  if ((ret->visibility() == elfcpp::STV_HIDDEN
       || ret->visibility() == elfcpp::STV_INTERNAL)
      && (ret->binding() == elfcpp::STB_GLOBAL
      || ret->binding() == elfcpp::STB_GNU_UNIQUE
      || ret->binding() == elfcpp::STB_WEAK)
      && !parameters->options().relocatable())

That means that there is no way to hide all symbols by default and override
with --dynamic-list or --export-dynamic-symbol .

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