Added safety checks to Array::xelem There's no reason to have a method which never checks invariants, ever. Added debugging checks to Array::xelem to help catch and debug out-of-bounds errors and reference overlap * configure.ac: Added configuration option for uniqueness-checking with xelem * jit-typeinfo.cc (octave_jit_paren_scalar): Call const Array::xelem rather than Array::xelem * Array-util.h, Array-util.cc (check_out_of_range): Extract common pattern to method (check_index): Methods to check index is in-bounds (compute_index): Added bool parameter check. does not check bounds when check is false and BOUNDS_CHECKING is off * Array.h, Array.cc (xelem): Use methods from Array-util.h to compute indices (is_unique): Check if this is the only reference to data * CmplxQR.cc, dbleQR.cc, fCmplxQR.cc, floatQR.cc (form): Move second assignment to after the call to xelem * lo-array-gripes.h, lo-array-gripes.cc (gripe_modifying_nonunique): Added error message for when non-const xelem is called on non-unique array

--- a/liboctave/numeric/CmplxQR.cc	Sat Jun 21 13:13:05 2014 -0600
+++ b/liboctave/numeric/CmplxQR.cc	Mon Jul 14 13:07:59 2014 -0600
@@ -159,13 +159,14 @@
         {
           // afact will become q.
           q = afact;
+          const ComplexMatrix& c_afact = afact;
           octave_idx_type k = qr_type == qr_type_economy ? n : m;
           r = ComplexMatrix (k, n);
           for (octave_idx_type j = 0; j < n; j++)
             {
               octave_idx_type i = 0;
               for (; i <= j; i++)
-                r.xelem (i, j) = afact.xelem (i, j);
+                r.xelem (i, j) = c_afact.xelem (i, j);
               for (; i < k; i++)
                 r.xelem (i, j) = 0;
             }