Also while adding a test for the fix for bug 88956 I noticed that GCC doesn't diagnose indexing into zero-length arrays.  The out-of-bounds accesses to the global zero-length arrays are folded to zero while those to the local ones are emitted.

$ gcc -O2 -S -Wall t.c
const char s1[1] = { };
int f1 (void)
{
  return s1[3];   // -Warray-bounds (good)
}

const char s0[0] = { };
int f0 (void)
{
  return s0[3];   // missing warning
}


int g1 (void)
{
  const char s1[1] = { };
  return s1[3];   // -Warray-bounds (good)
}

int g0 (void)
{
  const char s0[0] = { };
  return s0[3];   // missing warning
}

t.c: In function ‘f1’:
t.c:4:12: warning: array subscript 3 is above array bounds of ‘const char[1]’ [-Warray-bounds]
    4 |   return s1[3];   // -Warray-bounds (good)
      |          ~~^~~
t.c:1:12: note: while referencing ‘s1’
    1 | const char s1[1] = { };
      |            ^~
t.c: In function ‘g1’:
t.c:17:12: warning: array subscript 3 is above array bounds of ‘const char[1]’ [-Warray-bounds]
   17 |   return s1[3];   // -Warray-bounds (good)
      |          ~~^~~
t.c:16:14: note: while referencing ‘s1’
   16 |   const char s1[1] = { };
      |              ^~