1 files changed, 32 insertions, 1 deletions

diff --git a/sql/my_decimal.h b/sql/my_decimal.h
index e0c47029940..bd03782cb18 100644
--- a/sql/my_decimal.h
+++ b/sql/my_decimal.h
@@ -73,15 +73,30 @@ inline int my_decimal_int_part(uint precision, uint decimals)
 
 class my_decimal :public decimal_t
 {
+  /*
+    Several of the routines in strings/decimal.c have had buffer
+    overrun/underrun problems. These are *not* caught by valgrind.
+    To catch them, we allocate dummy fields around the buffer,
+    and test that their values do not change.
+   */
+#if !defined(DBUG_OFF)
+  int foo1;
+#endif
+
   decimal_digit_t buffer[DECIMAL_BUFF_LENGTH];
 
+#if !defined(DBUG_OFF)
+  int foo2;
+  static const int test_value= 123;
+#endif
+
 public:
 
   my_decimal(const my_decimal &rhs) : decimal_t(rhs)
   {
+    init();
     for (uint i= 0; i < DECIMAL_BUFF_LENGTH; i++)
       buffer[i]= rhs.buffer[i];
-    fix_buffer_pointer();
   }
 
   my_decimal& operator=(const my_decimal &rhs)
@@ -97,14 +112,30 @@ public:
 
   void init()
   {
+#if !defined(DBUG_OFF)
+    foo1= test_value;
+    foo2= test_value;
+#endif
     len= DECIMAL_BUFF_LENGTH;
     buf= buffer;
+    TRASH_ALLOC(buffer, sizeof(buffer));
   }
 
   my_decimal()
   {
     init();
   }
+  ~my_decimal()
+  {
+    sanity_check();
+  }
+
+  void sanity_check()
+  {
+    DBUG_ASSERT(foo1 == test_value);
+    DBUG_ASSERT(foo2 == test_value);
+  }
+
   void fix_buffer_pointer() { buf= buffer; }
 
   bool sign() const { return decimal_t::sign; }