Bug#19006: 4.0 valgrind problems (in test func_str)

On exactly-sized Strings, the String::c_ptr() function peeked beyond the
end of the buffer, possibly into unititialized space to see whether the 
buffer was NUL-terminated.

In a place that did peek improperly, we now use a c_ptr_safe() function, 
which doesn't peek where it shouldn't.


client/sql_string.h:
  Back-port String::c_ptr_safe().
sql/item_func.h:
  Describe side-effect behavior.
sql/item_strfunc.cc:
  Use the "_safe" version of c_ptr to avoid looking for a terminating 
  NUL character outside the initialized memory area.  Valgrind hates it 
  when one does that, and it theoretically could lead to a SEGV.
sql/sql_string.h:
  Back-port String::c_ptr_safe().

1 files changed, 8 insertions, 0 deletions

diff --git a/client/sql_string.h b/client/sql_string.h
index cffe78936a0..13687eef4dc 100644
--- a/client/sql_string.h
+++ b/client/sql_string.h
@@ -67,6 +67,14 @@ public:
       Ptr[str_length]=0;
     return Ptr;
   }
+  inline char *c_ptr_safe()
+  {
+    if (Ptr && str_length < Alloced_length)
+      Ptr[str_length]=0;
+    else
+      (void) realloc(str_length);
+    return Ptr;
+  }
 
   void set(String &str,uint32 offset,uint32 arg_length)
   {