[Bug debug/15810] New: DWARF2 does not emit 64 bit offsets when in 64 bit mode

["bdavis at macraigor dot com" <gcc-bugzilla at gcc dot gnu dot org>]

gcc -v:


Configured with: /rel/share/gnu/src/gcc-3.4.0/configure --host=i686-pc-cygwin -
-target=mips-elf --disable-nls --with-stabs --disable-install-libiberty --
disable-install-libbfd --disable-dependency-tracking --enable-64-bit-bfd --
enable-languages=c,c++ --with-gnu-as --with-gnu-ld
Thread model: single
gcc version 3.4.0

The code generated by gcc/dwarf2out.c doesn't generate 64 bit offsets when the 
compiler is compiling for a 64 bit target.  For example:

test.c:


int
main(int argc, char **argv)
{
    int a, b;

    b=1;
    a=b+1;
    return a;
}

then compile with:

mips-elf-gcc -g -EB -c -mips64 -mabi=64 test.c

Then look at debugging information (.debug_info):
mips-elf-objdump -xdgGrts test.o

You'll notice that the .debug_info section starts with
a 32 bit length.

However, when you link this .o with other 64 bit modules,
ld will insert an escaped 'ffffffff' 64-bit length at the
beginning of .debug_info.

This will cause gdb to mess up when it tries to parse .debug_info.

I created a simple source patch that works for me, though it may
not be general enough (I don't know):

*** gcc-3.4.0/gcc/dwarf2out.c	Thu Mar 18 13:29:32 2004
--- gcc-3.4.0-macraigor1/gcc/dwarf2out.c	Thu Jun  3 15:12:39 2004
***************
*** 271,277 ****
     as PTR_SIZE.  */
  
  #ifndef DWARF_OFFSET_SIZE
! #define DWARF_OFFSET_SIZE 4
  #endif
  
  /* According to the (draft) DWARF 3 specification, the initial length
--- 271,277 ----
     as PTR_SIZE.  */
  
  #ifndef DWARF_OFFSET_SIZE
! #define DWARF_OFFSET_SIZE DWARF2_ADDR_SIZE
  #endif
  
  /* According to the (draft) DWARF 3 specification, the initial length
***************
*** 286,291 ****
--- 286,295 ----
  #define DWARF_INITIAL_LENGTH_SIZE (DWARF_OFFSET_SIZE == 4 ? 4 : 12)
  #endif
  
+ #ifndef DWARF_CIE_OFFSET_SIZE
+ #define DWARF_CIE_OFFSET_SIZE 4
+ #endif
+ 
  #define DWARF_VERSION 2
  
  /* Round SIZE up to the nearest BOUNDARY.  */
***************
*** 1975,1987 ****
    /* Output the CIE.  */
    ASM_GENERATE_INTERNAL_LABEL (l1, CIE_AFTER_SIZE_LABEL, for_eh);
    ASM_GENERATE_INTERNAL_LABEL (l2, CIE_END_LABEL, for_eh);
!   dw2_asm_output_delta (for_eh ? 4 : DWARF_OFFSET_SIZE, l2, l1,
  			"Length of Common Information Entry");
    ASM_OUTPUT_LABEL (asm_out_file, l1);
  
    /* Now that the CIE pointer is PC-relative for EH,
       use 0 to identify the CIE.  */
!   dw2_asm_output_data ((for_eh ? 4 : DWARF_OFFSET_SIZE),
  		       (for_eh ? 0 : DW_CIE_ID),
  		       "CIE Identifier Tag");
  
--- 1979,1991 ----
    /* Output the CIE.  */
    ASM_GENERATE_INTERNAL_LABEL (l1, CIE_AFTER_SIZE_LABEL, for_eh);
    ASM_GENERATE_INTERNAL_LABEL (l2, CIE_END_LABEL, for_eh);
!   dw2_asm_output_delta (for_eh ? 4 : DWARF_CIE_OFFSET_SIZE, l2, l1,
  			"Length of Common Information Entry");
    ASM_OUTPUT_LABEL (asm_out_file, l1);
  
    /* Now that the CIE pointer is PC-relative for EH,
       use 0 to identify the CIE.  */
!   dw2_asm_output_data ((for_eh ? 4 : DWARF_CIE_OFFSET_SIZE),
  		       (for_eh ? 0 : DW_CIE_ID),
  		       "CIE Identifier Tag");
  
***************
*** 2100,2113 ****
        (*targetm.asm_out.internal_label) (asm_out_file, FDE_LABEL, for_eh + i 
* 2);
        ASM_GENERATE_INTERNAL_LABEL (l1, FDE_AFTER_SIZE_LABEL, for_eh + i * 2);
        ASM_GENERATE_INTERNAL_LABEL (l2, FDE_END_LABEL, for_eh + i * 2);
!       dw2_asm_output_delta (for_eh ? 4 : DWARF_OFFSET_SIZE, l2, l1,
  			    "FDE Length");
        ASM_OUTPUT_LABEL (asm_out_file, l1);
  
        if (for_eh)
  	dw2_asm_output_delta (4, l1, section_start_label, "FDE CIE offset");
        else
! 	dw2_asm_output_offset (DWARF_OFFSET_SIZE, section_start_label,
  			       "FDE CIE offset");
  
        if (for_eh)
--- 2104,2117 ----
        (*targetm.asm_out.internal_label) (asm_out_file, FDE_LABEL, for_eh + i 
* 2);
        ASM_GENERATE_INTERNAL_LABEL (l1, FDE_AFTER_SIZE_LABEL, for_eh + i * 2);
        ASM_GENERATE_INTERNAL_LABEL (l2, FDE_END_LABEL, for_eh + i * 2);
!       dw2_asm_output_delta (for_eh ? 4 : DWARF_CIE_OFFSET_SIZE, l2, l1,
  			    "FDE Length");
        ASM_OUTPUT_LABEL (asm_out_file, l1);
  
        if (for_eh)
  	dw2_asm_output_delta (4, l1, section_start_label, "FDE CIE offset");
        else
! 	dw2_asm_output_offset (DWARF_CIE_OFFSET_SIZE, section_start_label,
  			       "FDE CIE offset");
  
        if (for_eh)

-- 
           Summary: DWARF2 does not emit 64 bit offsets when in 64 bit mode
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: debug
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bdavis at macraigor dot com
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i686-pc-cygwin
GCC target triplet: mips-unknown-elf


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15810