[Bug fortran/91442] Wrong "may be used uninitialized" warning with allocation on assignment

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91442

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2019-08-14
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
test ()
{
  integer(kind=8) .string;
  character(kind=1)[1:.string] * string;

  string = 0B;
  {
    integer(kind=8) D.3904;
    integer(kind=8) D.3905;

    if (string != 0B) goto L.1;
    string = (character(kind=1)[1:.string] *) __builtin_malloc (12);
    goto L.2;
    L.1:;
    if (.string == 12) goto L.2;
    string = (character(kind=1)[1:.string] *) __builtin_realloc ((void *)
string, 12);
    L.2:;
    .string = 12;


see how we run into L.1 testing .string which was not set?  At -O0 we
didn't figure we never execute this path.  I suggest to initialize .string to
zero?

The early warning pass sees (conditionally executed)

  <bb 4> :
  if (.string_11(D) == 12)
    goto <bb 6>; [INV]
  else
    goto <bb 5>; [INV]

thus the "may" warning.  Alternatively just elide this check.