[Bug fortran/42112] overloaded function with allocatable result problem

["sgk at troutmask dot apl dot washington dot edu" <gcc-bugzilla@gcc.gnu.org>]

------- Comment #2 from sgk at troutmask dot apl dot washington dot edu  2009-11-20 00:20 -------
Subject: Re:  overloaded function with allocatable result problem

If the code is compiled with -fdump-tree-original one
immediately see the cause of the runtime error.  Eliminating
the common code in the dumps, I find this code

  pure function f() result(i)
    integer :: i
    integer, allocatable :: loc_ar(:)
    allocate(loc_ar(1))
    loc_ar = gen_g() ! does not work
    deallocate(loc_ar)
    i = 1
  end function f

generates

  f ()
  {
    g (&loc_ar);
  }

loc_ar has been allocated and the pointer to it is passed
to g() where is becomes associated with the result variable j.
You then try to allocate j, which is already allocated.


When you call g() directly in 

   pure function f() result(i)
    integer :: i
    integer, allocatable :: loc_ar(:)
    allocate(loc_ar(1))
    loc_ar = g() ! no problem here
    deallocate(loc_ar)
    i = 1
   end function f

the dump shows

  f ()
  {
    {
      integer(kind=8) D.1398;
      struct array1_integer(kind=4) atmp.1;
      integer(kind=8) D.1393;
      integer(kind=8) D.1392;
      integer(kind=8) D.1391;
      integer(kind=4)[0:] * restrict D.1390;

      D.1390 = (integer(kind=4)[0:] * restrict) loc_ar.data;
      D.1391 = loc_ar.offset;
      D.1392 = loc_ar.dim[0].lbound;
      D.1393 = loc_ar.dim[0].ubound;
      atmp.1.dtype = 265;
      atmp.1.data = 0B;
      atmp.1.offset = 0;
      g (&atmp.1);

g() is called with a unallocated temporary variable, so
your allocation in g() works.  The next several lines
copy atmp into loc_ar.

      D.1398 = NON_LVALUE_EXPR <D.1392>;
      {
      integer(kind=8) S.2;

      S.2 = 0;
      while (1)
        {
          if (atmp.1.dim[0].ubound - atmp.1.dim[0].lbound < S.2) goto L.2;
          (*D.1390)[(S.2 + D.1398) + D.1391]
                   = (*(integer(kind=4)[0:] * restrict) atmp.1.data)[S.2];
          S.2 = S.2 + 1;
        }
      L.2:;
    }

Here, the temporary variable is destroyed.

    {
      void * D.1397;

      D.1397 = (void *) atmp.1.data;
      if (D.1397 != 0B)
        {
          __builtin_free (D.1397);
        }
    }
  }
}

I need to go read the Fortran standard to determine the
semantics of a function returning an allocatable entity.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42112