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Re: Reference to .debug_loc

On Friday, February 14, 2003, at 10:26  AM, Daniel Jacobowitz wrote:

On Fri, Feb 14, 2003 at 03:57:55PM +0100, Michal Ludvig wrote:
Hi again,
when location lists are in use, .debug_info looks like this:

.section .debug_info
.long 0x187 # Length of Compilation Unit Info
.value 0x2 # DWARF version number
.long .Ldebug_abbrev0 # Offset Into Abbrev. Section
.byte 0x8 # Pointer Size (in bytes)
.uleb128 0x1 # (DIE (0xb) DW_TAG_compile_unit)
.long .Ldebug_line0 # DW_AT_stmt_list
.quad .Letext0 # DW_AT_high_pc
.quad .Ltext0 # DW_AT_low_pc
.byte 0x1 # DW_AT_language
.uleb128 0x3 # (DIE (0x50) DW_TAG_formal_parameter)
.long .LASF2 # DW_AT_name: "value"
.byte 0x1 # DW_AT_decl_file
.byte 0x2 # DW_AT_decl_line
.long 0x8f # DW_AT_type
.long .LLST0-.Ldebug_loc0 # DW_AT_location

So, the reference to .debug_loc on the last line of the example
(DW_AT_location) is an offset within that section, ie. it's 0 (NULL) for
the first entry with a location list. However when I link several .o
files together, each of them have DW_AT_location entries based at the
same NULL.

Err, why?
If they are in different files, it should be adjusting the offsets when it merges the sections together, no?

This time I realy can't see a way to find out at what position in the
resulting (ie. linked from several ones) .debug_loc should I start
reading for a given compilation unit.

Should there be something more in the CU header? Something similar to
.long   .Ldebug_abbrev0 # Offset Into Abbrev. Section
For example
.long   .Ldebug_loc0 # Offset Into Loclist Section


Or is there another way?
At a guess it should be like DW_AT_ranges:
        .long   .Ldebug_ranges0+0x0     # DW_AT_ranges

I.E. dw2_asm_output_offset, rather than dw2_asm_output_delta, in GCC.

It's supposed to be the offset from the beginning of the debug_loc section.
Will this do that?

Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

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