[Bug debug/49364] New: [4.7 regressions] Empty .debug_abbrev sections confuse SGI nm

[Bug debug/49364] New: [4.7 regressions] Empty .debug_abbrev sections confuse SGI nm

[ro at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49364

           Summary: [4.7 regressions] Empty .debug_abbrev sections confuse
                    SGI nm
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: ro@gcc.gnu.org
                CC: jakub@gcc.gnu.org
              Host: mips-sgi-irix6.5
            Target: mips-sgi-irix6.5
             Build: mips-sgi-irix6.5


I just looked at a couple of recent gnat.dg/lto*.adb testsuite failures that
started to occur between 20110322 and 20110401.  They fail like this:

collect2: error: /var/gcc/gcc-4.7.0-20110601/6.5-gcc/gcc/nm returned 1 exit
status
gnatlink: error when calling /var/gcc/gcc-4.7.0-20110601/6.5-gcc/gcc/xgcc
gnatmake: *** link failed.

I can see the nm failure if invoking nm manually:

> nm -Bng /var/gcc/gcc-4.7.0-20110601/6.5-gcc/mips-sgi-irix6.5/./libada/adainclude/ada.o > /dev/null
/var/gcc/gcc-4.7.0-20110601/6.5-gcc/mips-sgi-irix6.5/./libada/adainclude/ada.o
ERROR:  dwarf_elf_init:  DW_DLE_DEBUG_ABBREV_NULL 34 .debug_abbrev section
present but elf_getdata() failed or section is zero-length

And indeed the .debug_abbrev section is 0-length, as seen with elfdump -h:

          **** SECTION  HEADER  TABLE ****
[No]   Type                  Addr       Offset     Size        Name
       Link       Info       Adralgn    Entsize    Flags

[...]
[5]    SHT_MIPS_DWARF        0          0x68       0           .debug_abbrev
       0          0          0x1        0          0x00000000 

This is a regression from 4.6 where this worked correctly.  I'm attaching both
the 4.6 and 4.7 assembler files.

  Rainer

[Bug debug/49364] [4.7 regressions] Empty .debug_abbrev sections confuse SGI nm

[ro at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49364

--- Comment #1 from Rainer Orth <ro at gcc dot gnu.org> 2011-06-10 14:14:40 UTC ---
Created attachment 24488
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24488
gcc 4.6.0 assembler output

[Bug debug/49364] [4.7 regressions] Empty .debug_abbrev sections confuse SGI nm

[ro at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49364

--- Comment #2 from Rainer Orth <ro at gcc dot gnu.org> 2011-06-10 14:15:12 UTC ---
Created attachment 24489
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24489
gcc 4.7.0 assembler output

[Bug debug/49364] [4.7 regressions] Empty .debug_abbrev sections confuse SGI nm

[ro at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49364

Rainer Orth <ro at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.7.0

[Bug debug/49364] [4.7 regressions] Empty .debug_abbrev sections confuse SGI nm

[ro at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49364

Rainer Orth <ro at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011.06.29 10:21:54
                 CC|                            |mark at gcc dot gnu.org
     Ever Confirmed|0                           |1

--- Comment #3 from Rainer Orth <ro at gcc dot gnu.org> 2011-06-29 10:21:54 UTC ---
Caused by the fix for PR debug/49364.

[Bug debug/49364] [4.7 regressions] Empty .debug_abbrev sections confuse SGI nm

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49364

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-06-29 17:28:45 UTC ---
Created attachment 24636
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24636
gcc47-pr49364.patch

Ugh, broken vendor tools.
Anyway, does the following patch fix it?  There is no need to emit
the .debug_abbrev section at all in that case...

[Bug debug/49364] [4.7 regressions] Empty .debug_abbrev sections confuse SGI nm

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49364

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-06-30 10:26:38 UTC ---
Author: jakub
Date: Thu Jun 30 10:26:32 2011
New Revision: 175694

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=175694
Log:
    PR debug/49364
    * dwarf2out.c (output_abbrev_section): Don't return early
    if abbrev_die_table_in_use is 1.
    (dwarf2out_finish): Instead don't call output_abbrev_section
    nor emit abbrev_section_label in that case.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/dwarf2out.c

[Bug debug/49364] [4.7 regressions] Empty .debug_abbrev sections confuse SGI nm

[ro at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49364

Rainer Orth <ro at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
         AssignedTo|unassigned at gcc dot       |jakub at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #6 from Rainer Orth <ro at gcc dot gnu.org> 2011-07-04 17:26:37 UTC ---
As expected, the patch fixes the bug.

Thanks.
  Rainer