Re: `.sym' referenced in section `reloc_sym' of file.o: defined in discarded section `.text.sym' of file.o

[Alan Modra <amodra@bigpond.net.au>]

On Tue, May 16, 2006 at 05:28:41PM +0200, Etienne Lorrain wrote:
> --- Alan Modra <amodra@bigpond.net.au> wrote:
> > On Tue, May 16, 2006 at 01:34:25PM +0200, Etienne Lorrain wrote:
> > >  My problem is when the function (for instance) linux_set_params is not used
> > > at all in the link process, and is discarded because I am using GCC
> > > -ffunction-sections and LD --gc-sections, it is still referenced in
> > > ".section reloc_paramcode_section"
> > 
> > What is special about reloc_paramcode_section?  ie. How are you managing
> > to confuse the linker into thinking the reference in that section is not
> > a normal use, which should result in linux_set_params being kept?
> > 
> > Do you have a small self-contained testcase?
> 
>   I do not know what is special about reloc_paramcode_section, but I noticed

It's special because it is non-alloc, non-load.  --gc-sections does not
remove such sections, but does not treat their relocs specially.
ie. unless reloc_paramcode_section is itself referenced from somewhere,
its relocs will not be examined to see whether other sections referenced
by it should be kept.

See http://sources.redhat.com/ml/binutils/2004-08/msg00178.html  Perhaps
I should have restricted that change to sections without relocs.  That
would still keep sections like .comment and .note.GNU-stack, but drop
your "special" section.  I'm applying the following:

	* elflink.c (elf_gc_sweep): Don't specially keep non-alloc,
	non-load sections if they have relocs.

Index: bfd/elflink.c
===================================================================
RCS file: /cvs/src/src/bfd/elflink.c,v
retrieving revision 1.213
diff -u -p -r1.213 elflink.c
--- bfd/elflink.c	11 May 2006 15:55:40 -0000	1.213
+++ bfd/elflink.c	17 May 2006 00:28:23 -0000
@@ -8965,7 +8965,7 @@ elf_gc_sweep (bfd *abfd, struct bfd_link
 	{
 	  /* Keep debug and special sections.  */
 	  if ((o->flags & (SEC_DEBUGGING | SEC_LINKER_CREATED)) != 0
-	      || (o->flags & (SEC_ALLOC | SEC_LOAD)) == 0)
+	      || (o->flags & (SEC_ALLOC | SEC_LOAD | SEC_RELOC)) == 0)
 	    o->gc_mark = 1;
 
 	  if (o->gc_mark)


>  the message do not appear if --no-check-sections is not a parameter of ld !!!

That would be because you are hitting a fatal error without
--no-check-sections.

> ld: error: no memory region specified for loadable section `.rel.dyn'

-- 
Alan Modra
IBM OzLabs - Linux Technology Centre