Re: Reference to .debug_loc

[Daniel Jacobowitz <drow@mvista.com>]

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.
> 
> 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.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer