Linker garbage collection should not collect unreferenced symbols if they are externally visible and export-dynamic is on

[Sriraman Tallam]

Hi,

   There is a bug in gold. Linker garbage collection should not
collect unreferenced symbols if they are externally visible and
export-dynamic is on. They do right now. The following patch fixes it.

	* symtab.h (Symbol_table::gc_mark_symbol_for_shlib): Rename to
	gc_mark_symbol.
	* symtab.cc (Symbol_table::gc_mark_symbol_for_shlib): Rename to
	gc_mark_symbol.
	Change to just keep the section associated with symbol.
	(Symbol_table::add_from_relobj): Mark symbols as not garbage when
	they are externally visible and --export-dynamic is turned on.
	(Symbol_table::gc_mark_dyn_syms): Call gc_mark_symbol.

Comments?

Thanks,
-Sri.
-------------- next part --------------
Index: symtab.cc
===================================================================
RCS file: /cvs/src/src/gold/symtab.cc,v
retrieving revision 1.161
diff -u -u -p -r1.161 symtab.cc
--- symtab.cc	29 Sep 2011 17:04:36 -0000	1.161
+++ symtab.cc	27 Oct 2011 23:25:48 -0000
@@ -602,20 +602,16 @@ Symbol_table::gc_mark_undef_symbols(Layo
 }
 
 void
-Symbol_table::gc_mark_symbol_for_shlib(Symbol* sym)
+Symbol_table::gc_mark_symbol(Symbol* sym)
 {
-  if (!sym->is_from_dynobj() 
-      && sym->is_externally_visible())
+  //Add the object and section to the work list.
+  Relobj* obj = static_cast<Relobj*>(sym->object());
+  bool is_ordinary;
+  unsigned int shndx = sym->shndx(&is_ordinary);
+  if (is_ordinary && shndx != elfcpp::SHN_UNDEF)
     {
-      //Add the object and section to the work list.
-      Relobj* obj = static_cast<Relobj*>(sym->object());
-      bool is_ordinary;
-      unsigned int shndx = sym->shndx(&is_ordinary);
-      if (is_ordinary && shndx != elfcpp::SHN_UNDEF)
-        {
-          gold_assert(this->gc_!= NULL);
-          this->gc_->worklist().push(Section_id(obj, shndx));
-        }
+      gold_assert(this->gc_!= NULL);
+      this->gc_->worklist().push(Section_id(obj, shndx));
     }
 }
 
@@ -626,16 +622,7 @@ Symbol_table::gc_mark_dyn_syms(Symbol* s
 {
   if (sym->in_dyn() && sym->source() == Symbol::FROM_OBJECT
       && !sym->object()->is_dynamic())
-    {
-      Relobj* obj = static_cast<Relobj*>(sym->object()); 
-      bool is_ordinary;
-      unsigned int shndx = sym->shndx(&is_ordinary);
-      if (is_ordinary && shndx != elfcpp::SHN_UNDEF)
-        {
-          gold_assert(this->gc_ != NULL);
-          this->gc_->worklist().push(Section_id(obj, shndx));
-        }
-    }
+    gc_mark_symbol(sym);
 }
 
 // Make TO a symbol which forwards to FROM.
@@ -1251,11 +1238,16 @@ Symbol_table::add_from_relobj(
       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);
+      // Do not treat this symbol as garbage if this symbol will be
+      // exported to the dynamic symbol table.  This is true when
+      // building a shared library or using --export-dynamic and
+      // the symbol is externally visible.
+      if (parameters->options().gc_sections()
+	  && res->is_externally_visible()
+	  && !res->is_from_dynobj()
+          && (parameters->options().shared()
+	      || parameters->options().export_dynamic()))
+        this->gc_mark_symbol(res);
 
       if (is_defined_in_discarded_section)
 	res->set_is_defined_in_discarded_section();
Index: symtab.h
===================================================================
RCS file: /cvs/src/src/gold/symtab.h,v
retrieving revision 1.126
diff -u -u -p -r1.126 symtab.h
--- symtab.h	18 Oct 2011 00:25:52 -0000	1.126
+++ symtab.h	27 Oct 2011 23:25:48 -0000
@@ -1313,10 +1313,9 @@ class Symbol_table
   void
   gc_mark_undef_symbols(Layout*);
 
-  // During garbage collection, this ensures externally visible symbols
-  // are not treated as garbage while building shared objects.
+  // This tells garbage collection that this symbol is referenced.
   void
-  gc_mark_symbol_for_shlib(Symbol* sym);
+  gc_mark_symbol(Symbol* sym);
 
   // During garbage collection, this keeps sections that correspond to 
   // symbols seen in dynamic objects.