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From: "msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/99475] New: [10/11 Regression] bogus
 -Warray-bounds accessing an array element of empty structs
Date: Mon, 08 Mar 2021 22:32:33 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99475

            Bug ID: 99475
           Summary: [10/11 Regression] bogus -Warray-bounds accessing an
                    array element of empty structs
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

An indirect access to an element of an array of empty structs through a poi=
nter
to such an element triggers a spurious -Warray-bounds warning:

$ cat v.c && gcc -O2 -S -Wall v.c
struct S { } a[5];

void f (void)
{
  a[1] =3D (struct S) { };   // okay
}

void g (void)
{
  struct S *p =3D &a[0];
  p[1] =3D (struct S) { };   // bogus -Warray-bounds
}

v.c: In function =E2=80=98g=E2=80=99:
v.c:11:4: warning: array subscript 0 is outside array bounds of =E2=80=98st=
ruct S[5]=E2=80=99
[-Warray-bounds]
   11 |   p[1] =3D (struct S) { };
      |   ~^~~
v.c:1:14: note: while referencing =E2=80=98a=E2=80=99
    1 | struct S { } a[5];
      |              ^=