Re: RFA: Don't canonicalize STT_SECTION syms

[Daniel Jacobowitz <drow at false dot org>]

On Sat, Dec 11, 2004 at 03:27:51PM +1030, Alan Modra wrote:
> On Fri, Dec 10, 2004 at 11:34:26PM -0500, Daniel Jacobowitz wrote:
> > On Sat, Dec 11, 2004 at 02:50:43PM +1030, Alan Modra wrote:
> > > On Fri, Dec 10, 2004 at 10:19:29AM -0500, Daniel Jacobowitz wrote:
> > > > so I assume there is more.
> > > 
> > > Yeah.
> > > 
> > > bfd/ChangeLog
> > > 	* elfcode.h (elf_slurp_symbol_table): Use bfd_elf_sym_name so that
> > > 	canonical sections syms have a name.
> > 
> > Could you explain why this change is necessary?  It's not going back to
> > the same place we were before, and I find this...
> 
> Well, you either have this change, revert your change that stopped use
> of the section symbol for relocs, or introduce some elf dependecy into
> objdump.  Otherwise objdump -r won't display a name for relocs against
> section syms.

OK, now I see the problem.

> > > -0+00 l    d  foo	0+0 
> > > +0+00 l    d  foo	0+0 (|foo)
> > 
> > to be pretty confusing, since IIRC an undefined reference to foo
> > shouldn't be resolved to that symbol, if the ELF symbol's name is
> > empty.
> 
> How is this different from other local symbols?

Like this.  Output from my system tools, i.e. well before this patch.

drow@nevyn:~/qtmp% cat foo.s
.section "foo"
        .word 0
drow@nevyn:~/qtmp% cat bar.s
.section "bar"
        .word foo
drow@nevyn:~/qtmp% as -o foo.o foo.s
drow@nevyn:~/qtmp% as -o bar.o bar.s
drow@nevyn:~/qtmp% readelf -s foo.o bar.o

File: foo.o

Symbol table '.symtab' contains 5 entries:
   Num:    Value  Size Type    Bind   Vis      Ndx Name
     0: 00000000     0 NOTYPE  LOCAL  DEFAULT  UND
     1: 00000000     0 SECTION LOCAL  DEFAULT    1
     2: 00000000     0 SECTION LOCAL  DEFAULT    2
     3: 00000000     0 SECTION LOCAL  DEFAULT    3
     4: 00000000     0 SECTION LOCAL  DEFAULT    4

File: bar.o

Symbol table '.symtab' contains 6 entries:
   Num:    Value  Size Type    Bind   Vis      Ndx Name
     0: 00000000     0 NOTYPE  LOCAL  DEFAULT  UND
     1: 00000000     0 SECTION LOCAL  DEFAULT    1
     2: 00000000     0 SECTION LOCAL  DEFAULT    2
     3: 00000000     0 SECTION LOCAL  DEFAULT    3
     4: 00000000     0 SECTION LOCAL  DEFAULT    4
     5: 00000000     0 NOTYPE  GLOBAL DEFAULT  UND foo
drow@nevyn:~/qtmp% ld -r -o foo foo.o bar.o
drow@nevyn:~/qtmp% readelf -s foo

Symbol table '.symtab' contains 11 entries:
   Num:    Value  Size Type    Bind   Vis      Ndx Name
     0: 00000000     0 NOTYPE  LOCAL  DEFAULT  UND
     1: 00000000     0 SECTION LOCAL  DEFAULT    1
     2: 00000000     0 SECTION LOCAL  DEFAULT    2
     3: 00000000     0 SECTION LOCAL  DEFAULT    3
     4: 00000000     0 SECTION LOCAL  DEFAULT    4
     5: 00000000     0 SECTION LOCAL  DEFAULT    5
     6: 00000000     0 SECTION LOCAL  DEFAULT    6
     7: 00000000     0 SECTION LOCAL  DEFAULT    7
     8: 00000000     0 SECTION LOCAL  DEFAULT    8
     9: 00000000     0 SECTION LOCAL  DEFAULT    9
    10: 00000000     0 NOTYPE  GLOBAL DEFAULT  UND foo
drow@nevyn:~/qtmp% objdump -t foo

foo:     file format elf32-i386

SYMBOL TABLE:
00000000 l    d  .text  00000000
00000000 l    d  .data  00000000
00000000 l    d  .bss   00000000
00000000 l    d  foo    00000000
00000000 l    d  bar    00000000
00000000 l    d  *ABS*  00000000
00000000 l    d  *ABS*  00000000
00000000 l    d  *ABS*  00000000
00000000 l    d  *ABS*  00000000
00000000         *UND*  00000000 foo

If that showed both of these:

00000000 l    d  foo    00000000 foo
00000000         *UND*  00000000 foo

I'd be really confused!  "Why didn't 'foo' resolve to 'foo'?" the user
asks me...

-- 
Daniel Jacobowitz