Should the section address be ignored when processing DWARF information ?

[Nick Clifton <nickc at redhat dot com>]

Hi Eric,

  Does Mach-O need to have the section address added in to the offset
  calculation when processing DWARF information ?

  Currently the code in binutils/dwarf.c adds the section address to
  the offsets it calculates when processing DWARF information.  For
  ELF based systems this is a no-op since the section address will be
  0.  For COFF based systems, and in particular for Cygwin, the
  section addresses will not be zero, but adding in the section
  address results in bogus offsets.  The offsets are meant to be
  section relative, so it would seem to me that adding in the section
  address is the wrong thing to do.

  The patch below removes this addition of the section address, and
  although I have tested it locally with lots of different toolchains,
  I have not been able to test in under Mach-O.  Would this patch
  break Mach-O compatibility ?  If so, do you think that it would it be
  appropriate to add special case code for Mach-O ?

Cheers
  Nick

2007-04-17  Corinna Vinschen  <vinschen@redhat.com>

	* dwarf.c (display_debug_str): 

Index: binutils/dwarf.c
===================================================================
RCS file: /cvs/src/src/binutils/dwarf.c,v
retrieving revision 1.12
diff -c -3 -p -r1.12 dwarf.c
*** binutils/dwarf.c	9 Apr 2007 14:36:59 -0000	1.12
--- binutils/dwarf.c	17 Apr 2007 10:49:36 -0000
*************** process_debug_info (struct dwarf_section
*** 1673,1679 ****
        else
  	process_abbrev_section
  	  ((unsigned char *) debug_displays [abbrev].section.start
! 	   + compunit.cu_abbrev_offset - debug_displays [abbrev].section.address,
  	   (unsigned char *) debug_displays [abbrev].section.start
  	   + debug_displays [abbrev].section.size);
  
--- 1673,1679 ----
        else
  	process_abbrev_section
  	  ((unsigned char *) debug_displays [abbrev].section.start
! 	   + compunit.cu_abbrev_offset,
  	   (unsigned char *) debug_displays [abbrev].section.start
  	   + debug_displays [abbrev].section.size);
  
*************** display_debug_loc (struct dwarf_section 
*** 2377,2383 ****
  	{
  	  has_frame_base = debug_information [i].have_frame_base [j];
  	  /* DWARF sections under Mach-O have non-zero addresses.  */
! 	  offset = debug_information [i].loc_offsets [j] - section->address; 
  	  next = section_begin + offset;
  	  base_address = debug_information [i].base_address;
  
--- 2377,2383 ----
  	{
  	  has_frame_base = debug_information [i].have_frame_base [j];
  	  /* DWARF sections under Mach-O have non-zero addresses.  */
! 	  offset = debug_information [i].loc_offsets [j]; 
  	  next = section_begin + offset;
  	  base_address = debug_information [i].base_address;