[Bug libfortran/31286] New: cshift uses uninitialized variables

[burnus at gcc dot gnu dot org]

As found by Salvatore Filippone using valgrind.

-----------------------
program testcshft

integer :: alist(4)

!!$alist = (/1,2,3,4/)
alist =cshift(alist,-1)
write(*,*) alist
end program testcshft
------------------------- 

==6801== Conditional jump or move depends on uninitialised value(s)
> ==6801==    at 0x1B98AF30: cshift0 (cshift0.c:193)
> ==6801==    by 0x8048673: MAIN__


Analysis by me:

alist = cshift(alist,-1)

This calls  cshift0(ret, array, shift, which, size)
where size = GFC_DESCRIPTOR_RANK (array)
and "which" is the dimension (not given -> 1)
Thus: which == size == 1.

In cshift0 one finds:
  which = which - 1;
  for (dim = 0; dim < GFC_DESCRIPTOR_RANK (array); dim++)
    {
      if (dim == which) { ... }
      else
        { sstride[n] = ... }
    }

  if (sstride[0] == 0)

That is: If which == rank of the array, sstride gets never initialized.

Index: libgfortran/intrinsics/cshift0.c
===================================================================
*** libgfortran/intrinsics/cshift0.c    (revision 123083)
--- libgfortran/intrinsics/cshift0.c    (working copy)
*************** cshift0 (gfc_array_char * ret, const gfc
*** 103,108 ****
--- 103,110 ----
      runtime_error ("Argument 'DIM' is out of range in call to 'CSHIFT'");

    which = which - 1;
+   sstride[0] = 0;
+   rstride[0] = 0;

    extent[0] = 1;
    count[0] = 0;


-- 
           Summary: cshift uses uninitialized variables
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: wrong-code, patch
          Severity: normal
          Priority: P3
         Component: libfortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: burnus at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31286