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Patch to fix a bug with version scripts and gc-sections in the GOLD linker.

Sriraman Tallam tmsriram@google.com
Fri Jul 22 22:39:00 GMT 2011 
Hi,

    Gold garbage collection does not do the right thing with this program:

foobar.cc
--------------
extern "C"
int bar()
{
  return 144;
}

extern "C"
int foo()
{
  return 121;
}

sym.ver  (version_script)
-----------
{
	 global:
		 foo;
	 local:
		 bar;
};



$ g++ -fPIC -shared -Wl,--gc-sections foobar.cc -o foobar.so
-Wl,--version-script,sym.ver
$ nm foobar.so | grep bar
00000000000066a t bar

Function bar is not garbage collected even though it is local.

This simple patch fixes it.

	* symtab.cc (Symbol_table::gc_mark_symbol_for_shlib): Check if symbol
	is not forced local before marking it as referenced.
	(Symbol_table::add_from_relobj): Mark symbol as referenced only after
	checking if they cannot be forced local.



Ok to submit?

Thanks,
-Sri.
-------------- next part --------------
Index: symtab.cc
===================================================================
RCS file: /cvs/src/src/gold/symtab.cc,v
retrieving revision 1.157
diff -u -u -p -r1.157 symtab.cc
--- symtab.cc	8 Jul 2011 23:49:11 -0000	1.157
+++ symtab.cc	22 Jul 2011 21:40:19 -0000
@@ -605,7 +605,8 @@ void
 Symbol_table::gc_mark_symbol_for_shlib(Symbol* sym)
 {
   if (!sym->is_from_dynobj() 
-      && sym->is_externally_visible())
+      && sym->is_externally_visible()
+      && !sym->is_forced_local())
     {
       //Add the object and section to the work list.
       Relobj* obj = static_cast<Relobj*>(sym->object());
@@ -1238,15 +1239,15 @@ Symbol_table::add_from_relobj(
 				  is_default_version, *psym, st_shndx,
 				  is_ordinary, orig_st_shndx);
       
+      if (is_forced_local)
+	this->force_local(res);
+
       // If building a shared library using garbage collection, do not 
       // treat externally visible symbols as garbage.
       if (parameters->options().gc_sections() 
           && parameters->options().shared())
         this->gc_mark_symbol_for_shlib(res);
 
-      if (is_forced_local)
-	this->force_local(res);
-
       if (is_defined_in_discarded_section)
 	res->set_is_defined_in_discarded_section();
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