add error policy to check return

git-svn-id: svn://svn.code.sf.net/p/loki-lib/code/trunk@908 7ec92016-0320-0410-acc4-a06ded1c099a

include/loki/CheckReturn.h

@@ -17,6 +17,8 @@
 
 
 #include <assert.h>
+#include <stdio.h>
+
 
 namespace Loki
 {
@@ -42,7 +44,26 @@ namespace Loki
 ///  can work with other types that have cheap copy operations.
 ////////////////////////////////////////////////////////////////////////////////
 
-template < class Value >
+
+struct TriggerAssert
+{
+	static void run()
+	{
+        assert( 0 );
+	}
+};
+
+
+struct FprintfStderr
+{
+	static void run()
+	{
+		fprintf(stderr, "CheckReturn: return value was not checked\n");
+	}
+};
+
+
+template < class Value , typename OnError = TriggerAssert>
 class CheckReturn
 {
 public:
@@ -61,9 +82,10 @@ public:
     /// Destructor checks if return value was used.
     inline ~CheckReturn( void )
     {
-        // If this assertion fails, then a function failed to check the
+		// If m_checked is false, then a function failed to check the
         // return value from a function call.
-        assert( m_checked );
+		if (!m_checked)
+			OnError::run();
     }
 
     /// Conversion operator changes CheckReturn back to Value type.

test/CheckReturn/main.cpp

@@ -26,6 +26,8 @@ typedef ::Loki::CheckReturn< bool > BoolReturn;
 
 typedef ::Loki::CheckReturn< string > StringReturn;
 
+typedef ::Loki::CheckReturn< bool , ::Loki::FprintfStderr > BoolReturnStderr;
+
 
 // ----------------------------------------------------------------------------
 
@@ -41,6 +43,14 @@ BoolReturn CheckRequired( void )
     return BoolReturn( true );
 }
 
+// ----------------------------------------------------------------------------
+
+BoolReturnStderr CheckRequiredStderr( void )
+{
+    return BoolReturnStderr( true );
+}
+
+
 // ----------------------------------------------------------------------------
 
 BoolReturn CheckRequired( bool value )
@@ -143,6 +153,11 @@ int main( unsigned int argc, const char * argv[] )
         cout << "Made a nested call to CheckRequired." << endl;
     }
 
+	{
+		BoolReturnStderr check = CheckRequiredStderr();
+	}
+	cout << "There should be a error message: \nCheckReturn: return value was not checked" << endl;
+
     // This should assert since caller does not check return value.
     CheckRequired();
     cout << "Should assert before this line!  How did we get here?" << endl;