Re: Linker does not detect unresolved symbol

[Alan Modra <amodra at gmail dot com>]

On Mon, Jan 25, 2010 at 12:10:29PM +0100, Stern, Eli wrote:
> Is this a bug or a misuse of the tools?

A bug.  The code that reports undefined symbols says this:

      /* If we have an undefined symbol reference here then it must have
	 come from a shared library that is being linked in.  (Undefined
	 references in regular files have already been handled).  */

and indeed does not report an error if the symbol is referred to in a
regular file (! h->ref_regular check a little below the comment).

However, because you are using --gc-sections and the section with the
reference in the regular file is garbage collected, you don't get a
report for the reference in the regular object file..

This patch gives you an error, but doesn't report the right reference
since ld only tracks the first file that references a symbol.

	* elflink.c (elf_link_output_extsym): Do not ignore undefined
	symbols with ref_regular set when gc_sections is active.

Index: bfd/elflink.c
===================================================================
RCS file: /cvs/src/src/bfd/elflink.c,v
retrieving revision 1.366
diff -u -p -r1.366 elflink.c
--- bfd/elflink.c	21 Jan 2010 14:54:40 -0000	1.366
+++ bfd/elflink.c	25 Jan 2010 14:11:45 -0000
@@ -8590,7 +8590,7 @@ elf_link_output_extsym (struct elf_link_
       /* If we are reporting errors for this situation then do so now.  */
       if (ignore_undef == FALSE
 	  && h->ref_dynamic
-	  && ! h->ref_regular
+	  && (!h->ref_regular || finfo->info->gc_sections)
 	  && ! elf_link_check_versioned_symbol (finfo->info, bed, h)
 	  && finfo->info->unresolved_syms_in_shared_libs != RM_IGNORE)
 	{

-- 
Alan Modra
Australia Development Lab, IBM