fix more cppcheck warnings

cppcheck now passes, with a few false positives

see https://github.com/jcupitt/libvips/issues/331

TODO

@@ -1,3 +1,9 @@
+- try vips_shrink() in two passes: first, sum horizontal strips, second sum
+  vertical
+
+  we would then only need to demand the source a line at a time, and the
+  intermediate image would be much smaller ... possible cache savings as well
+
 - add bandjoinconst ... append a band (or bands?) from a constant
 
   see https://github.com/jcupitt/libvips/issues/325

libvips/arithmetic/complex.c

@@ -21,6 +21,8 @@
  * 	- redo as a class
  * 21/11/11
  * 	- add vips_complexget()
+ * 29/9/15
+ * 	- return 0 for cross-product where one arg is zero
  */
 
 /*
@@ -411,16 +413,28 @@ G_DEFINE_TYPE( VipsComplex2, vips_complex2, VIPS_TYPE_BINARY );
 #ifdef USE_MODARG_DIV
 
 #define CROSS( Q, X1, Y1, X2, Y2 ) { \
-	double arg = atan2( X2, X1 ) - atan2( Y2, Y1 ); \
-	\
-	Q[0] = cos( arg ); \
-	Q[1] = sin( arg ); \
+	if( ((X1) == 0.0 && (Y1) == 0.0) || \
+		((X2) == 0.0 && (Y2) == 0.0) ) { \
+		Q[0] = 0.0; \
+		Q[1] = 0.0; \
+	} \
+	else { \
+		double arg = atan2( X2, X1 ) - atan2( Y2, Y1 ); \
+		\
+		Q[0] = cos( arg ); \
+		Q[1] = sin( arg ); \
+	} \
 }
 
 #else /* USE_MODARG_DIV */
 
 #define CROSS( Q, X1, Y1, X2, Y2 ) { \
-	if( ABS( Y1 ) > ABS( Y2 ) ) { \
+	if( ((X1) == 0.0 && (Y1) == 0.0) || \
+		((X2) == 0.0 && (Y2) == 0.0) ) { \
+		Q[0] = 0.0; \
+		Q[1] = 0.0; \
+	} \
+	else if( ABS( Y1 ) > ABS( Y2 ) ) { \
 		double a = Y2 / Y1; \
 		double b = Y1 + Y2 * a; \
 		double re = (X1 + X2 * a) / b; \
@@ -455,7 +469,9 @@ vips_complex2_buffer( VipsArithmetic *arithmetic,
 	int x;
 
 	switch( cmplx->cmplx ) {
-	case VIPS_OPERATION_COMPLEX2_CROSS_PHASE:	SWITCH2( CROSS ); break;
+	case VIPS_OPERATION_COMPLEX2_CROSS_PHASE:	
+		SWITCH2( CROSS ); 
+		break;
 
 	default:
 		g_assert( 0 );

libvips/iofuncs/object.c

@@ -759,9 +759,8 @@ vips_object_get_argument( VipsObject *object, const char *name,
 			_( "no vips argument named `%s'" ), name );
 		return( -1 );
 	}
-	if( argument_class &&
-		!(*argument_instance = vips__argument_get_instance( 
-			*argument_class, object )) ) {
+	if( !(*argument_instance = vips__argument_get_instance( 
+		*argument_class, object )) ) {
 		vips_error( class->nickname, 
 			_( "argument `%s' has no instance" ), name );
 		return( -1 );
@@ -1313,12 +1312,6 @@ vips_object_get_property( GObject *gobject,
 	VipsArgumentInstance *argument_instance =
 		vips__argument_get_instance( argument_class, object );
 
-	if( !argument_class ) {
-		G_OBJECT_WARN_INVALID_PROPERTY_ID( gobject,
-			property_id, pspec );
-		return;
-	}
-
 	g_assert( ((VipsArgument *) argument_class)->pspec == pspec );
 
 	if( !argument_instance->assigned ) {