[Bug fortran/52151] New: Segfault with realloc on assignment and RESHAPE to unallocated LHS

["burnus at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52151

             Bug #: 52151
           Summary: Segfault with realloc on assignment and RESHAPE to
                    unallocated LHS
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: burnus@gcc.gnu.org
                CC: pault@gcc.gnu.org


Follow up to PR 52012 and 52117.

* B is allocated with the shape (n1,n2,n3):
  -> Works since the patch for PR 52012
  (Before, it had the wrong result for the last two elements)

* B is not allocated
  -> Segfault since the patch for PR 52012
  -> Before: no segfault but wrong result in for the last two elements

* B allocated with shape (1,1,1)
  -> Since patch for PR 52012: No crash, but wrong result ("2.0" and 3.0 appear
     multiple times, 5., 6., 7., 8. are missing and 4. is at the wrong
position)
  -> Before: no segfault but wrong result in for the last two elements

The test case has been taken from PR 52117 with adaption to show this bug.
chapter08/puppeteer_f2003 of Damian's/Xia's/Xu's book is also affected.


I think there might be an ordering issue with regards to the zero condition and
the bounds condition. Something like the following might work (completely
untested; note also the "ORIF"):

--- trans-expr.c        (revision 183971)
+++ trans-expr.c        (working copy)
@@ -6296 +6296 @@ fcncall_realloc_result (gfc_se *se, int
-  tree zero_cond;
+  tree zero_cond, cond;
@@ -6324,0 +6325 @@ fcncall_realloc_result (gfc_se *se, int
+  cond = boolean_true_node;
@@ -6344 +6345 @@ fcncall_realloc_result (gfc_se *se, int
-                                  zero_cond);
+                                  cond);
@@ -6345,0 +6347,4 @@ fcncall_realloc_result (gfc_se *se, int
+
+   zero_cond = fold_build2_loc (input_location, TRUTH_ORIF_EXPR,
+                               boolean_type_node, zero_cond,
+                               cond);



! Based on the example of PR 52117 by Steven Hirshman
      PROGRAM RESHAPEIT
      INTEGER, PARAMETER :: n1=2, n2=2, n3=2
      INTEGER            :: m1, m2, m3, lc
      REAL, ALLOCATABLE  :: A(:,:), B(:,:,:)
      REAL               :: val

      ALLOCATE (A(n1,n2*n3))
! <<< No allocation: Segfault
!      ALLOCATE (B(1,1,1))    ! << Does not segfault, but result is wrong
!      ALLOCATE (B(n1,n2,n3)) ! << WORKS

      val = 0
      lc = 0
      DO m3=1,n3
         DO m2=1,n2
            lc = lc+1
            DO m1=1,n1
               val = val+1
               A(m1, lc) = val
            END DO
         END DO
      END DO

      B = RESHAPE(A, [n1,n2,n3])

      lc = 0
      DO m3=1,n3
         DO m2=1,n2
            lc = lc+1
            DO m1=1,n1
               PRINT *,'A(',m1,',',lc,') = ',A(m1,lc),' B = ',B(m1,m2,m3)
               if (A(m1,lc) /= B(m1,m2,m3)) call abort ()
            END DO
         END DO
      END DO
      DEALLOCATE(A, B)
      END PROGRAM RESHAPEIT