[Bug middle-end/73550] New: Another wrong -Wmaybe-uninitialized warning in switch statement

[amker at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=73550

            Bug ID: 73550
           Summary: Another wrong -Wmaybe-uninitialized warning in switch
                    statement
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amker at gcc dot gnu.org
  Target Milestone: ---

Hi,
GCC trunk gives wrong -Wmaybe-uninitialized warning message on below switch
statement:


int fun1 (int, int);
int fun2 (int, int);
int fun3 (int, int);
void swap (int *, int *);
void abort (void);
void bar (void);
void foo (int code, int x, int a, int b)
{
  int (*fp) (int, int);

  switch (code)
    {
    case 1:
      if (x == 1)
        {
          fp = fun3;
          break;
        }
    case 2:
      swap (&a, &b);
    case 3:
    case 4:
      fp = fun1;
      break;
    case 11:
      if (x == 1)
        {
          fp = fun3;
          break;
        }
    case 12:
      swap (&a, &b);
    case 13:
    case 14:
      fp = fun2;
      break;
    case 5:
    case 6:
    case 7:
    case 8:
      break;
    default:
      abort ();
    }

  switch (code)
    {
    case 1:
    case 3:
    case 11:
    case 13:
      fp (a, b);
      bar ();
      break;
    case 2:
    case 4:
    case 12:
    case 14:
      fp (a, b);
      break;
    case 5:
    case 6:
    case 7:
    case 8:
      bar ();
      break;
    default:
      abort ();
    }
  return;
}

Compiled with:
$ ./gcc -O2 -S x.c -o x.S -Wmaybe-uninitialized
produces:
x.c: In function ‘foo’:
x.c:53:7: warning: ‘fp’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
       fp (a, b);
       ^~~~~~~~~

GCC is configured as:
../gcc/configure --prefix=... --disable-bootstrap --disable-libssp
--disable-libgomp --disable-libsanitizer --disable-libitm --disable-atomic
CXXFLAGS='-g -O0' --enable-languages=c,c++