[Bug fortran/55789] Needless realloc

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55789

Tobias Burnus <burnus at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-12-22
                 CC|                            |burnus at gcc dot gnu.org
     Ever Confirmed|0                           |1

--- Comment #1 from Tobias Burnus <burnus at gcc dot gnu.org> 2012-12-22 18:24:45 UTC ---
(In reply to comment #0)
> In trying to understand some memory leak reported by mtrace (which turns out, 
> I think, to be a bug in glibc 
> http://sourceware.org/bugzilla/show_bug.cgi?id=14981)

Using GLIBC 2.17, no memleak is reported here for neither the C program nor
this PR's Fortran code.


> I noticed that the following code
> performs both an allocate and a reallocate in cp_1d_i4_sort.


Confirmed. With GCC 4.5, only a simple malloc is done; ltrace shows:
  malloc(4)

but starting from GCC 4.6 both malloc and realloc are invoked; ltrace has:
  malloc(4)
  realloc(0xafbf90, 8)


With 4.8, one has (slightly simplified):

    ubound.0 = (arr->dim[0].ubound - arr->dim[0].lbound) + 1;
    atmp.4.dim[0].lbound = 0;
    atmp.4.dim[0].ubound = ubound.0-1;
    D.1907 = ubound.0 <= 0 ? 0 : ubound.0 * 4;
    atmp.4.data = __builtin_malloc (MAX_EXPR <D.1907, 1>);
...
    D.1919 = MAX_EXPR<(D.1918->dim[0].ubound - D.1918->dim[0].lbound) + 1, 0>;
      shadow_loopvar.7 = 1;
      atmp.4.dim[0].ubound = atmp.4.dim[0].ubound
              + MAX_EXPR <(D.1919 - shadow_loopvar.7) + 1, 0>;
      atmp.4.data = __builtin_realloc (atmp.4.data,
                                       (atmp.4.dim[0].ubound + 1) * 4);
      while (1)
        {
          if (shadow_loopvar.7 > D.1919) goto L.1;
          (*atmp.4.data)[offset.5] = shadow_loopvar.7;
          offset.5 = offset.5 + 1;
          shadow_loopvar.7 = shadow_loopvar.7 + 1;
        }
      L.1:;