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List:       gcc-bugs
Subject:    [Bug c/98902] New: -fmerge-all-constants leaves dangling reference
From:       astrange at ithinksw dot com via Gcc-bugs <gcc-bugs () gcc ! gnu ! org>
Date:       2021-01-31 14:19:04
Message-ID: bug-98902-4 () http ! gcc ! gnu ! org/bugzilla/
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98902

            Bug ID: 98902
           Summary: -fmerge-all-constants leaves dangling reference
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: astrange at ithinksw dot com
  Target Milestone: ---

This source:
--
#include <stdio.h>

static const int a1[] = {1};
static const int a2[] = {1};

int main (void)
{
        printf("%p %p\n", a1, a2);
        return 0;
}
--

produces code where it doesn't emit 'a2' but still references it:
--
.LC0:
        .string "%p %p\n"
main:
        sub     rsp, 8
        mov     edx, OFFSET FLAT:a2
        mov     esi, OFFSET FLAT:a1
        xor     eax, eax
        mov     edi, OFFSET FLAT:.LC0
        call    printf
        xor     eax, eax
        add     rsp, 8
        ret
a1:
        .long   1
--

with '-O2 -fmerge-all-constants'. Did not verify this locally, just in compiler
explorer.=
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