[Bug gold/15758] New: Gold segfault when using -q option

[law at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15758

            Bug ID: 15758
           Summary: Gold segfault when using -q option
           Product: binutils
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gold
          Assignee: ian at airs dot com
          Reporter: law at redhat dot com
                CC: ccoutant at google dot com

gold is segfaulting when linking the following testcode.

t.c (compile with -fPIC):

__thread int a;

void _start(void) {
    a = 2;
}



Starting program: /tmp/binutils/gold/ld-new t.o -q

Breakpoint 3, gold::Sized_relobj_file<64, false>::emit_relocs_scan
(this=0xa644f0, symtab=0x7fffffff7980, layout=0x7fffffff7be0,
    plocal_syms=0x7ffff7ffb468 "", p=...) at
/home/law/UPSTREAM/binutils/gold/reloc.cc:550
550       gold_assert(rr != NULL);
(gdb) c
Continuing.

Breakpoint 3, gold::Sized_relobj_file<64, false>::emit_relocs_scan
(this=0xa644f0, symtab=0x7fffffff7980, layout=0x7fffffff7be0,
    plocal_syms=0x7ffff7ffb468 "", p=...) at
/home/law/UPSTREAM/binutils/gold/reloc.cc:550
550       gold_assert(rr != NULL);
(gdb) bt
#0  gold::Sized_relobj_file<64, false>::emit_relocs_scan (this=0xa644f0,
symtab=0x7fffffff7980, layout=0x7fffffff7be0, plocal_syms=0x7ffff7ffb468 "",
    p=...) at /home/law/UPSTREAM/binutils/gold/reloc.cc:550
#1  0x00000000006c5d68 in gold::Sized_relobj_file<64, false>::do_scan_relocs
(this=0xa644f0, symtab=0x7fffffff7980, layout=0x7fffffff7be0, rd=0xa4a770)
    at /home/law/UPSTREAM/binutils/gold/reloc.cc:469
#2  0x00000000006c2c7a in gold::Relobj::scan_relocs (this=0xa644f0,
symtab=0x7fffffff7980, layout=0x7fffffff7be0, rd=0xa4a770)
    at /home/law/UPSTREAM/binutils/gold/object.h:1057
#3  0x00000000006c27c1 in gold::Scan_relocs::run (this=0xa69020) at
/home/law/UPSTREAM/binutils/gold/reloc.cc:188
#4  0x000000000073e38b in gold::Workqueue::find_and_run_task
(this=0x7fffffff7630, thread_number=0) at
/home/law/UPSTREAM/binutils/gold/workqueue.cc:319
#5  0x000000000073e9b4 in gold::Workqueue::process (this=0x7fffffff7630,
thread_number=0) at /home/law/UPSTREAM/binutils/gold/workqueue.cc:495
#6  0x0000000000404016 in main (argc=3, argv=0x7fffffffdb68) at
/home/law/UPSTREAM/binutils/gold/main.cc:252
(gdb) p rr
$5 = (gold::Relocatable_relocs *) 0x0


It appears the relocatable_relocs are set up in:

gold::Sized_relobj_file

  for (std::vector<unsigned int>::const_iterator p = reloc_sections.begin();
       p != reloc_sections.end();
       ++p)
[ ... ]
     Output_section* data_section = out_sections[data_shndx];
      if (data_section == reinterpret_cast<Output_section*>(2))
        {
          // The layout for the data section was deferred, so we need
          // to defer the relocation section, too.
          const char* name = pnames + shdr.get_sh_name();
          this->deferred_layout_relocs_.push_back(
              Deferred_layout(i, name, pshdr, 0, elfcpp::SHT_NULL));
          out_sections[i] = reinterpret_cast<Output_section*>(2);
          out_section_offsets[i] = invalid_address;
          continue;
        }
      if (data_section == NULL)
        {
          out_sections[i] = NULL;
          out_section_offsets[i] = invalid_address;
          continue;
        }

      Relocatable_relocs* rr = new Relocatable_relocs();
      this->set_relocatable_relocs(i, rr);

We have no appropriate out_section for the section reloc section.  Thus
data_section is NULL and we call this->set_relocatable_relocs, ultimately
leading to the assertion failure.

I'm not at all familiar with the gold code, so I'm not sure how to proceed at
the moment.  Your thoughts would be appreciated.

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