forcing to emit absolute addresses in the .debug_loc setion

[Umesh Kalappa <umesh dot kalappa0 at gmail dot com>]

Hi Guys,

Myself was very new  to dwarf debugging format and recently we migrate
GCC compiler  to 4.8.3 toolchain from 4.5.2 ans using same binutils
2.23.51.

we are seeing the  weird issue with .debug_loc entries and assembler
pop up with below error


/tmp/ccUj1tbg.s: Assembler messages:
/tmp/ccUj1tbg.s:778: Error: can't resolve `.LVL0' {.text section} -
`.text._ZN10__cxxabiv117__array_type_infoD2Ev' {*UND* section}
/tmp/ccUj1tbg.s:779: Error: can't resolve `.LVL1' {.text section} -
`.text._ZN10__cxxabiv117__array_type_infoD2Ev' {*UND* section}
/tmp/ccUj1tbg.s:782: Error: can't resolve `.LVL1' {.text section} -
`.text._ZN10__cxxabiv117__array_type_infoD2Ev' {*UND* section}

corresponding .debug_loc entries

.section        .debug_loc,info
.Ldebug_loc0:
.LLST0:
        .4byte  .LVL0-.text._ZN10__cxxabiv117__array_type_infoD2Ev
        .4byte  .LVL1-1-.text._ZN10__cxxabiv117__array_type_infoD2Ev
        .2byte  0x1
        .byte   0x54
        .4byte  .LVL1-1-.text._ZN10__cxxabiv117__array_type_infoD2Ev
        .4byte  .LFE72-.text._ZN10__cxxabiv117__array_type_infoD2Ev
        .2byte  0x4
        .byte   0xf3
        .uleb128 0x1
        .byte   0x54
        .byte   0x9f
        .4byte  0
        .4byte  0


googling on the above issue was with  no luck :( ,after going through
the dwarf format it was found that ,the above .debug_loc entries are
relatively not absloute,please correct me here if my assumption was
wrong and we need to stick to dwarf-2 format not to  like 3,4, or 5 .

second,was tweaked/forced the compiler to generate abs address like

static void
output_loc_list (dw_loc_list_ref list_head)
{

  else if (/*!have_multiple_function_sections*/0) //our hacked thing
and weird too
        {
          dw2_asm_output_delta (DWARF2_ADDR_SIZE, curr->begin, curr->section,
                                "Location list begin address (%s)",
                                list_head->ll_symbol);
          dw2_asm_output_delta (DWARF2_ADDR_SIZE, curr->end, curr->section,
                                "Location list end address (%s)",
                                list_head->ll_symbol);
        }
      else
        {
          dw2_asm_output_addr (DWARF2_ADDR_SIZE, curr->begin,
                               "Location list begin address (%s)",
                               list_head->ll_symbol);
          dw2_asm_output_addr (DWARF2_ADDR_SIZE, curr->end,
                               "Location list end address (%s)",
                               list_head->ll_symbol);
        }

}

now the .debug_loc section looks like

.section        .debug_loc,info
.Ldebug_loc0:
.LLST0:
        .4byte  .LVL0
        .4byte  .LVL1-1
        .2byte  0x1
        .byte   0x54
        .4byte  .LVL1-1
        .4byte  .LFE72
        .2byte  0x4
        .byte   0xf3
        .uleb128 0x1
        .byte   0x54
        .byte   0x9f
        .4byte  0
        .4byte  0

now everything goes well,But we are looking the cause and proper fix too.


So please guys, pass us your insights / suggestion / comments  on this.

Thank you
~Umesh