Pre-asserts to clarify buffer usage
diff --git a/tinyxml2.cpp b/tinyxml2.cpp
index dd8e3fd..ca6c566 100755
--- a/tinyxml2.cpp
+++ b/tinyxml2.cpp
@@ -1997,6 +1997,7 @@
         // Close out and re-start the va-args

         va_end( va );

         va_start( va, format );

+        TIXMLASSERT( _buffer.Size() > 0 && _buffer[_buffer.Size() - 1] == 0 );

         char* p = _buffer.PushArr( len ) - 1;	// back up over the null terminator.

 #if defined(_MSC_VER) && (_MSC_VER >= 1400 )

 		#if defined(WINCE)

diff --git a/tinyxml2.h b/tinyxml2.h
index 1f6c833..d0017b6 100755
--- a/tinyxml2.h
+++ b/tinyxml2.h
@@ -276,6 +276,7 @@
     }

 

     int Size() const					{

+        TIXMLASSERT( _size >= 0 );

         return _size;

     }