Fixed an aliasing bug in the set_subm(), set_rowm(), and set_colm()

functions.  It was possible that you could get incorrect results
if you used these functions to copy one part of a matrix to another
part of the same matrix if the two areas overlapped.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402305

dlib/matrix/matrix_utilities.h

@@ -1531,6 +1531,8 @@ namespace dlib
                 << "\n\trect.height() (target matrix):  " << rect.height()
                 );
 
+            if (exp.destructively_aliases(m) == false)
+            {
                 long r_exp = 0;
                 for (long r = rect.top(); r <= rect.bottom(); ++r)
                 {
@@ -1542,6 +1544,13 @@ namespace dlib
                     }
                     ++r_exp;
                 }
+            }
+            else
+            {
+                // make a temporary copy of the matrix we are going to assign to m to 
+                // avoid aliasing issues during the copy
+                this->operator=(tmp(exp));
+            }
 
             return *this;
         }
@@ -1638,10 +1647,19 @@ namespace dlib
                 << "\n\tm.nr() (target matrix):   " << m.nr()
                 );
 
+            if (exp.destructively_aliases(m) == false)
+            {
                 for (long i = 0; i < m.nr(); ++i)
                 {
                     m(i,col) = exp(i);
                 }
+            }
+            else
+            {
+                // make a temporary copy of the matrix we are going to assign to m to 
+                // avoid aliasing issues during the copy
+                this->operator=(tmp(exp));
+            }
 
             return *this;
         }
@@ -1708,10 +1726,19 @@ namespace dlib
                 << "\n\tm.nc() (target matrix):   " << m.nc()
                 );
 
+            if (exp.destructively_aliases(m) == false)
+            {
                 for (long i = 0; i < m.nc(); ++i)
                 {
                     m(row,i) = exp(i);
                 }
+            }
+            else
+            {
+                // make a temporary copy of the matrix we are going to assign to m to 
+                // avoid aliasing issues during the copy
+                this->operator=(tmp(exp));
+            }
 
             return *this;
         }

dlib/test/matrix.cpp

@@ -1206,6 +1206,24 @@ namespace
 
             DLIB_CASSERT(m1 == res, "m1: \n" << m1 << "\nres: \n" << res);
 
+            set_subm(m1,0,0,5,5) = m1*m1;
+            DLIB_CASSERT(m1 == res*res, "m1: \n" << m1 << "\nres*res: \n" << res*res);
+
+            m1 = res;
+            set_subm(m1,1,1,2,2) = subm(m1,0,0,2,2);
+
+            long res_vals2[] = {
+                9, 9, 9, 9, 9,
+                0, 9, 9, 0, 0,
+                0, 0, 1, 0, 2,
+                0, 0, 2, 2, 2,
+                0, 0, 2, 2, 0
+            };
+
+            res = res_vals2;
+            DLIB_CASSERT(m1 == res, "m1: \n" << m1 << "\nres: \n" << res);
+
+
         }
 
         {