[Bug middle-end/81962] -Wmaybe-uninitialized refers to wrong line (and only works with -O3) (Fortran)

[Bug middle-end/81962] -Wmaybe-uninitialized refers to wrong line (and only works with -O3) (Fortran)

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81962

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|https://gcc.gnu.org/bugzill |
                   |a/show_bug.cgi?id=63943     |
                 CC|                            |msebor at gcc dot gnu.org
             Status|NEW                         |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #5 from Martin Sebor <msebor at gcc dot gnu.org> ---
This is, in fact, a duplicate of pr63943.

A C test case that reproduces the same effect is below.  I doubt this will ever
be perfect.

$ cat a.c && gcc -O2 -S -Wall -fdump-tree-uninit-lineno=/dev/stdout a.c
int z;

void f (int i)
{
  z = i + 1;
}

void g (int a, int b, int c)
{
  int x;
  if (a && b)
    x = a + b;

  if (b && c) 
    f (x + 1);
}

;; Function f (f, funcdef_no=0, decl_uid=1944, cgraph_uid=1, symbol_order=1)

void f (int i)
{
  int _1;

  <bb 2> [local count: 1073741824]:
  [a.c:5:9] _1 = i_2(D) + 1;
  [a.c:5:5] z = _1;
  [a.c:6:1] return;

}



;; Function g (g, funcdef_no=1, decl_uid=1949, cgraph_uid=2, symbol_order=2)

...

a.c: In function ‘g’:
a.c:5:9: warning: ‘x’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
    5 |   z = i + 1;
      |       ~~^~~
a.c:10:7: note: ‘x’ was declared here
   10 |   int x;
      |       ^
void g (int a, int b, int c)
{
  int x;
  _Bool _1;
  _Bool _2;
  _Bool _3;
  _Bool _4;
  _Bool _5;
  int _14;

  <bb 2> [local count: 1073741824]:
  [a.c:11:7] _1 = a_8(D) != 0;
  [a.c:11:9] _2 = b_9(D) != 0;
  [a.c:11:9] _3 = _1 & _2;
  [a.c:11:6] if (_3 != 0)
    goto <bb 3>; [50.00%]
  else
    goto <bb 7>; [50.00%]

  <bb 7> [local count: 536870912]:
  goto <bb 4>; [100.00%]

  <bb 3> [local count: 536870913]:
  [a.c:12:7] x_11 = a_8(D) + b_9(D);

  <bb 4> [local count: 1073741824]:
  # x_6 = PHI <x_10(D)(7), [a.c:12:7] x_11(3)>
  [a.c:14:9] _4 = c_12(D) != 0;
  [a.c:14:9] _5 = _2 & _4;
  [a.c:14:6] if (_5 != 0)
    goto <bb 5>; [50.00%]
  else
    goto <bb 8>; [50.00%]

  <bb 8> [local count: 536870912]:
  goto <bb 6>; [100.00%]

  <bb 5> [local count: 536870913]:
  [a.c:5:9] _14 = x_6 + 2;
  [a.c:5:5] z = _14;

  <bb 6> [local count: 1073741824]:
  [a.c:16:1] return;

}

*** This bug has been marked as a duplicate of bug 63943 ***