PR16867, linking object with separate debug file

This teaches the DWARF2 find_line functions how to deal with separate
debug relocatable object files.  Also fixes a major bug:
When _bfd_dwarf2_slurp_debug_info was split out, place_sections ran
after .debug_info was relocated.  This defeated the whole purpose of
place_sections.  See the comment I added before place_sections.
Fixes some minor bugs too:
- place_sections didn't set VMA for alloc but non-load sections (bss).
- zero size sections can have symbols, so they need their VMA set too.
- last_vma was incorrectly adjusted.
- my last change to place_sections left VMA unchanged for .debug_info
  when the linker has mapped input to output sections, but this is
  wrong since bfd_simple_get_relocated_section_contents unmaps debug
  sections.

	PR 16867
	* dwarf2.c: Formatting.
	(struct dwarf2_debug): Make adjusted_section_count signed.
	(unset_sections): Make i signed.
	(set_debug_vma): New function.
	(place_sections): Handle separate debug object file.  Set VMA
	on debug sections, even if they have an output section.  Also
	set VMA on zero size sections, and non-load but alloc sections.
	Set adjusted_section_count to -1 when no section adjustment.
	Malloc adjusted_sections.  Don't double last_vma.  Transfer
	alloc section VMAs to separate debug file.
	(_bfd_dwarf2_cleanup_debug_info): Free adjusted_sections.
	(_bfd_dwarf2_slurp_debug_info): Add do_place parameter.  Drop
	test on symbols being the same before using old stash.  Read
	and use separate debug file symbols.  Call place_sections.
	(find_line): Don't call place_sections here.
	* libbfd-in.h (_bfd_dwarf2_slurp_debug_info): Update proto.
	* libbfd.h: Regenerate.
	* mach-o.c (bfd_mach_o_find_nearest_line): Adjust
	_bfd_dwarf2_slurp_debug_info call.
	* simple.c (simple_save_output_info): Clarify comment.

1 files changed, 16 insertions, 9 deletions

diff --git a/bfd/simple.c b/bfd/simple.c
index 55a5554..1331f9b 100644
--- a/bfd/simple.c
+++ b/bfd/simple.c
@@ -106,6 +106,22 @@ struct saved_offsets
   struct saved_output_info *sections;
 };
 
+/* The sections in ABFD may already have output sections and offsets
+   set if we are here during linking.
+
+   DWARF-2 specifies offsets into debug sections in many cases and
+   bfd_simple_get_relocated_section_contents is called to relocate
+   debug info for a single relocatable object file.  So we want
+   offsets relative to that object file's sections, not offsets in the
+   output file.  For that reason, reset a debug section->output_offset
+   to zero.
+
+   If not called during linking then set section->output_section to
+   point back to the input section, because output_section must not be
+   NULL when calling the relocation routines.
+
+   Save the original output offset and section to restore later.  */
+
 static void
 simple_save_output_info (bfd *abfd ATTRIBUTE_UNUSED,
 			 asection *section,
@@ -220,15 +236,6 @@ bfd_simple_get_relocated_section_contents (bfd *abfd,
       outbuf = data;
     }
 
-  /* The sections in ABFD may already have output sections and offsets set.
-     Because this function is primarily for debug sections, and GCC uses the
-     knowledge that debug sections will generally have VMA 0 when emitting
-     relocations between DWARF-2 sections (which are supposed to be
-     section-relative offsets anyway), we need to reset the output offsets
-     to zero.  We also need to arrange for section->output_section->vma plus
-     section->output_offset to equal section->vma, which we do by setting
-     section->output_section to point back to section.  Save the original
-     output offset and output section to restore later.  */
   saved_offsets.section_count = abfd->section_count;
   saved_offsets.sections = malloc (sizeof (*saved_offsets.sections)
 				   * saved_offsets.section_count);