[gold][patch] Fix problem where unsatisfied reference to vtable causes a misleading error message

[Cary Coutant <ccoutant at google dot com>]

This patch fixes a problem where an unsatisfied reference to a vtable
causes the linker to print an error message "requires unsupported
dynamic reloc; recompile with -fPIC" (in addition to the undefined
symbol error). This happened because we were still creating a dynamic
relocation for the unsatisfied reference.

The Target_*::Scan::check_non_pic() routines in several of the targets
(all except i386, I think) still have a problem where they print that
error message even when we're not building a shared library. This
patch bypasses the most likely case where we would hit that problem,
but I'll follow up with a separate patch to catch any remaining cases
where that might happen.

OK to commit?

-cary


	* symtab.h (needs_plt_entry): Check for unsatisfied reference from
	an executable.
	(needs_dynamic_reloc): Likewise.


Index: symtab.h
===================================================================
RCS file: /cvs/src/src/gold/symtab.h,v
retrieving revision 1.87
diff -u -p -r1.87 symtab.h
--- symtab.h	17 Mar 2009 07:07:21 -0000	1.87
+++ symtab.h	24 Mar 2009 20:25:35 -0000
@@ -530,6 +530,10 @@ class Symbol
   bool
   needs_plt_entry() const
   {
+    // An undefined symbol from an executable does not need a PLT entry.
+    if (this->is_undefined() && !parameters->options().shared())
+      return false;
+
     return (!parameters->doing_static_link()
             && this->type() == elfcpp::STT_FUNC
             && (this->is_from_dynobj()
@@ -561,10 +565,10 @@ class Symbol
     if (parameters->doing_static_link())
       return false;

-    // A reference to a weak undefined symbol from an executable should be
+    // A reference to an undefined symbol from an executable should be
     // statically resolved to 0, and does not need a dynamic relocation.
     // This matches gnu ld behavior.
-    if (this->is_weak_undefined() && !parameters->options().shared())
+    if (this->is_undefined() && !parameters->options().shared())
       return false;

     // A reference to an absolute symbol does not need a dynamic relocation.