qsort isn't guaranteed to be a stable sort, that is, elements
comparing equal according to the comparison function may be reordered
relative to their original ordering. Of course sometimes you may not
care, but even in those cases it is good to force some ordering
(ie. not have the comparison function return 0) so that linker output
is reproducible over different libc qsort implementations.
One way to make qsort stable (which the glibc manual incorrectly says
is the only way) is to augment the elements being sorted with a
monotonic counter of some kind, and use that counter as the final
arbiter of ordering in the comparison function.
Another way is to set up an array of pointers into the array of
elements, first pointer to first element, second pointer to second
element and so so, and sort the pointer array rather than the element
array. Final arbiter in the comparison function then is the pointer
difference. This works well with, for example, the symbol pointers
returned by _bfd_elf_canonicalize_symtab which point into a symbol
array.
This patch fixes a few places where sorting by symbol pointers is
appropriate, and adds comments where qsort stability is a non-issue.
* elf-strtab.c (strrevcmp): Comment.
* merge.c (strrevcmp): Likewise.
* elf64-ppc.c (compare_symbols): Correct final pointer comparison.
Comment on why comparing pointers ensures a stable sort.
* elflink.c (struct elf_symbol): Add void* to union.
(elf_sort_elf_symbol): Ensure a stable sort with pointer comparison.
(elf_sym_name_compare): Likewise.
(bfd_elf_match_symbols_in_sections): Style fix.
(elf_link_sort_cmp1): Comment.
Not padding string merge section output to its alignment can cause
failures of the S-record tests when input string merge sections are
padded, since the ELF linker output for the single string section
would shrink compared to the SREC linker output. That might result in
following sections having different addresses.
On the other hand, padding string merge section output when input
string merge sections are *not* padded can also cause failures, in
this case due to the ELF linker output for the string section being
larger (due to padding) than the SREC linker output.
It would be better to write a more robust test, but it is also nice
to leave input unchanged when no string merges occur.
PR 24311
* merge.c (merge_strings): Return secinfo. Don't pad section
to alignment here.
(_bfd_merge_sections): Pad section to alignment here, if input
sections contributing to merged output all pad to alignment.
Formatting.
I was looking at Debian bug #874674 again today, and think I might
have spotted the problem. It appears that merge.c tries to cope with
memory allocation failures in some circumstances, but doesn't quite
manage to get everything right. This patch will make ld report memory
allocation failures instead of silently not merging strings.
* merge.c (merge_strings): Return FALSE on malloc failure.
(_bfd_merge_sections): Return failures from record_section and
merge_strings.
This patch adds --compress-debug-sections=[none|zlib|zlib-gnu|zlib-gabi]
to ld for ELF targets to support generating compressed DWARF debug
sections. We always generate .zdebug_* section since section names have
been finalized and they can't be changed easily when compression is
being performed.
bfd/
* bfd-in.h (compressed_debug_section_type): New.
* compress.c (bfd_compress_section_contents): Add an argument
for linker write compression and always generate .zdebug_*
section when linking.
(bfd_init_section_compress_status): Pass FALSE to
bfd_compress_section_contents.
(bfd_compress_section): New function.
* elf.c (elf_fake_sections): For linking, set SEC_ELF_COMPRESS
on DWARF debug sections if COMPRESS_DEBUG is set and rename
section if COMPRESS_DEBUG_GABI_ZLIB isn't set.
(assign_file_positions_for_non_load_sections): Set sh_offset
to -1 if SEC_ELF_COMPRESS is set.
(assign_file_positions_except_relocs): Likwise.
(_bfd_elf_assign_file_positions_for_relocs): Renamed to ...
(_bfd_elf_assign_file_positions_for_non_load): This. Change
return time to bfd_boolean. Compress the section if
SEC_ELF_COMPRESS is set.
(_bfd_elf_write_object_contents): Updated.
(_bfd_elf_set_section_contents): Write section contents to
the buffer if SEC_ELF_COMPRESS is set.
* merge.c: Include "elf-bfd.h".
(sec_merge_emit): Add arguments for contents and offset. Write
to contents with offset if contents isn't NULL.
(_bfd_write_merged_section): Write section contents to the
buffer if SEC_ELF_COMPRESS is set. Pass contents and
output_offset to sec_merge_emit.
* elflink.c (bfd_elf_final_link): Allocate the buffer for
output section contents if SEC_ELF_COMPRESS is set.
* section.c (SEC_ELF_COMPRESS): New.
* bfd-in2.h: Regenerated.
gas/
* as.h (compressed_debug_section_type): Removed.
include/
* bfdlink.h (bfd_link_info): Add compress_debug.
ld/
* ld.texinfo: Document --compress-debug-sections=.
* ldmain.c (main): Set BFD_COMPRESS on output_bfd if
COMPRESS_DEBUG is set. Set BFD_COMPRESS_GABI on output_bfd
for COMPRESS_DEBUG_GABI_ZLIB.
* lexsup.c (elf_static_list_options): Add
--compress-debug-sections=.
* emultempl/elf32.em (OPTION_COMPRESS_DEBUG): New.
(xtra_long): Add "compress-debug-sections".
(gld${EMULATION_NAME}_handle_option): Handle
OPTION_COMPRESS_DEBUG.
ld/testsuite/
* ld-elf/compress.exp (build_tests): Add tests for
--compress-debug-sections=.
(run_tests): Likewise.
Add additonal tests for --compress-debug-sections=.
* ld-elf/gabiend.rt: New file.
* ld-elf/gabinormal.rt: Likewise.
* ld-elf/gnubegin.rS: Likewise.
* ld-elf/gnunormal.rS: Likewise.
* ld-elf/zlibbegin.rS: Likewise.
* ld-elf/zlibnormal.rS: Likewise.
(record_section): Likewise.
(_bfd_merge_sections): Likewise.
(_bfd_merged_section_offset): Properly handle NULL secinfo.
(_bfd_add_merge_section): Allocate extra space for a zero
terminator on SEC_STRINGS sections.
unsigned int. Cast RELOC_BASE10, RELOC_BASE13 and RELOC_BASE22 to
unsigned int.
(NAME(aout,final_link)): Cast enum used in assignment.
(aout_link_write_symbols): Cast enums in comparisons, int values to
boolean, enums in assignments to int.
(aout_link_input_section_std): Cast rel->r_index to unsigned int.
(aout_link_input_section_ext): Likewise. Cast enums used in comparisons
with unsigned ints.
(aout_link_reloc_link_order): Cast enum to int in assignment.
* archive.c (_bfd_generic_read_ar_hdr_mag): Cast result of memchr
calls to char *.
* bfd-in.h (bfd_set_section_vma): Cast enum true to unsigned int in
assignment.
* bfd-in2.h (bfd_set_section_vma): Likewise.
* bfd.c (bfd_record_phdr): Cast enums in assignments.
* binary.c (bfd_alloc): Cast enum to long.
* coffgen.c (_bfd_coff_is_local_label_name): Cast return to boolean.
* dwarf2.c (read_abbrevs): Add casts to enum types.
(read_attribute_value): Likewise.
(arange_add): Cast result of bfd_zalloc call.
(comp_unit_contains_address): Return true and false.
(comp_unit_find_nearest_line): Cast return to boolean.
* format.c (bfd_check_format_matches, bfd_set_format): Likewise.
* gen-aout.c: define macro '_' if not defined.
* libbfd.c (bfd_realloc): Cast malloc and realloc to PTR.
(bfd_bwrite): Cast bfd_realloc to bfd_byte *.
(bfd_write_bigendian_4byte_int): Cast return to boolean.
(bfd_seek): Cast bfd_realloc to bfd_byte *.
(bfd_generic_is_local_label_name): Cast return to boolean.
* libcoff.h (_bfd_coff_adjust_symndx): Remove extraneous '\'.
* linker.c (_bfd_link_hash_newfunc): Cast bfd_hash_allocate result to
struct bfd_hash_entry *.
(_bfd_generic_link_hash_newfunc): likewise.
(_bfd_generic_final_link): Cast enum to unsigned int.
* merge.c (sec_merge_emit): Cast return to boolean.
(merge_strings): Add casts to const unsigned char *.
* reloc.c (bfd_get_reloc_code_name): Cast enums in comparison to int.
(bfd_generic_get_relocated_section_content): Cast enum to unsigned int.
* section.c (bfd_section_hash_newfunc): Cast bfd_hash_allocate result to
struct bfd_hash_entry *.
(bfd_set_section_content): Add cast to PTR in comparison.
* simple.c (simple_dummy_warning, simple_dummy_undefined_symbol,
simple_dummy_reloc_overflow, simple_dummy_reloc_dangerous,
simple_dummy_unattached_reloc,
bfd_simple_get_relocated_section_contents): Add K&R declarations and
function definitions.
* srec.c (S3Forced): Initialize to false.
(srec_get_symtab): Cast return value from bfd_alloc to asymbol *.
* stabs.c (_bfd_link_section_stabs): Cast enum to int in comparisons.
(_bfd_discard_section_stabs): Likewise. Also cast return to boolean.
* syms.c (bfd_is_undefined_symclass): Cast return to boolean.
(_bfd_stab_section_find_nearest_line): Cast enum to bfd_byte in
comparisons.
