[Bug gold/15478] -no-as-needed required to avoid runtime symbol lookup error

[ccoutant at google dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15478

--- Comment #10 from Cary Coutant <ccoutant at google dot com> 2013-05-20 
17:41:58 UTC ---
> That is rather explicit, isn't it? For gold to match this behavior, I
> think all we need to do is remove the test for sym->in_reg() in the
> following code in Symbol_table::set_dynsym_indexes:
>
>  // If the symbol is defined in a dynamic object and is
>  // referenced strongly in a regular object, then mark the
>  // dynamic object as needed.  This is used to implement
>  // --as-needed.
>  if (sym->is_from_dynobj()
>      && sym->in_reg()
>      && !sym->is_undef_binding_weak())
>    sym->object()->set_is_needed();

Close, but not quite. If the symbol isn't referenced from the main
program, we won't be adding a dynsym entry for it, so the test for
as-needed needs to be copied to the if clause just above:

diff --git a/gold/symtab.cc b/gold/symtab.cc
index 2e17529..595df56 100644
--- a/gold/symtab.cc
+++ b/gold/symtab.cc
@@ -2381,7 +2381,17 @@ Symbol_table::set_dynsym_indexes(unsigned int index,
       // and without a version.

       if (!sym->should_add_dynsym_entry(this))
-       sym->set_dynsym_index(-1U);
+       {
+         sym->set_dynsym_index(-1U);
+         // If the symbol is defined in a dynamic object and is
+         // referenced strongly in a dynamic object, then mark the
+         // dynamic object as needed.  This is used to implement
+         // --as-needed.  This is for compatibility with the GNU
+         // linker.
+         if (sym->is_from_dynobj()
+             && !sym->is_undef_binding_weak())
+           sym->object()->set_is_needed();
+       }
       else if (!sym->has_dynsym_index())
        {
          sym->set_dynsym_index(index);

I've added a test case for this, too. Ian, if you think this is
reasonable, I'll go ahead and commit it.

-cary

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