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Subject: [Bug lto/97290] Segmentation fault in lto-wrapper
Date: Wed, 07 Oct 2020 06:53:12 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D97290

--- Comment #8 from Martin Li=C5=A1ka <marxin at gcc dot gnu.org> ---
Fixed on master with g:190c04ba36d9c6c3dce41f12012aa97c6d7f22f5

commit 190c04ba36d9c6c3dce41f12012aa97c6d7f22f5
Author: Martin Liska <mliska@suse.cz>
Date:   Mon Oct 5 18:03:08 2020 +0200

    lto: fix LTO debug sections copying.

    readelf -S prints:

    There are 81999 section headers, starting at offset 0x1f488060:

    Section Headers:
      [Nr] Name              Type            Address          Off    Size  =
 ES
Flg Lk Inf Al
      [ 0]                   NULL            0000000000000000 000000 01404f=
 00=20
   81998   0  0
      [ 1] .group            GROUP           0000000000000000 000040 000008=
 04=20
   81995 105027  4
    ...
      [81995] .symtab           SYMTAB          0000000000000000 d5d9298 2d=
b310
18     81997 105026  8
      [81996] .symtab_shndx     SYMTAB SECTION INDICES 0000000000000000 d8b=
45a8
079dd8 04     81995   0  4
      [81997] .strtab           STRTAB          0000000000000000 d92e380 80=
460c
00      0   0  1
    ...

    Looking at the documentation:
    Table 7=E2=80=9315 ELF sh_link and sh_info Interpretation

    sh_type - sh_link
    SHT_SYMTAB - The section header index of the associated string table.
    SHT_SYMTAB_SHNDX - The section header index of the associated symbol ta=
ble.

    As seen, sh_link of a SHT_SYMTAB always points to a .strtab and readelf
    confirms that.

    So we need to use reverse mapping taken from
      [81996] .symtab_shndx     SYMTAB SECTION INDICES 0000000000000000 d8b=
45a8
079dd8 04     81995   0  4

    where sh_link points to 81995.

    libiberty/ChangeLog:

            PR lto/97290
            * simple-object-elf.c (simple_object_elf_copy_lto_debug_section=
s):
            Use sh_link of a .symtab_shndx section.=