[lld] r361830 - Reland D61583 [ELF] Error on relocations to STT_SECTION symbols if the sections were discarded
Stephan Bergmann via llvm-commits
llvm-commits at lists.llvm.org
Fri Jun 7 00:18:18 PDT 2019
With bisecting, I found that the below commit breaks the debuginfo in my
Linux LibreOffice builds that use lld with --gdb-index. I wasn't able
to reduce the test case in any meaningful way, but what I observe is
that a gdb backtrace will print source information for some of the
frames, but for others will only print the .so pathname. I could not
reproduce with a small test executable, but the shared libraries
involved in LibreOffice can be rather large, so maybe the issue is
related to size. The backtraces look fine when I rebuild LibreOffice
without using --gdb-index (though I appear to have some issue with
"step" commands in gdb not stepping into function calls even then, but
didn't investigate that further).
(I see that this commit has yesterday been reverted in r362739 and then
re-reverted in r362743, so I assume the situation on trunk hasn't
effectively changed from what I observed with my build from earlier this
On 28/05/2019 16:34, Fangrui Song via llvm-commits wrote:
> Author: maskray
> Date: Tue May 28 07:34:28 2019
> New Revision: 361830
> URL: http://llvm.org/viewvc/llvm-project?rev=361830&view=rev
> Reland D61583 [ELF] Error on relocations to STT_SECTION symbols if the sections were discarded
> This is implemented by creating Undefined (instead of Defined) for such
> local STT_SECTION symbols. It allows us to catch errors when there are
> relocations to such discarded sections (e.g. in PR41693, ld.bfd and gold
> error but we don't). Updated comdat-discarded-error.s checks we emit
> friendly error message.
> For relocatable-eh-frame.s, ld.lld -r a.o a.o will now error
> "STT_SECTION symbol should be defined" because the section .eh_frame
> refers to is now an Undefined instead of a Defined.
> So I have to change `error()` to `warn()` to retain the output.
> rLLD361144 inadvertently enabled the error for --gdb-index
> (in LLDDwarfObj<ELFT>::findAux()).
> Relocations from .debug_info (not in comdat) to .text.* (in comdat) for
> DW_AT_low_pc are common. If an .text.* was discarded, rLLD361144 would error,
> which was unexpected. (Note, if we don't error as this patch does,
> InputSection::relocateNonAlloc() will resolve such relocations).
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