--- src/zimg/colorspace/matrix3.cpp_old	2021-08-02 16:27:28.737949184 +0800
+++ src/zimg/colorspace/matrix3.cpp	2021-08-02 16:27:48.394167745 +0800
@@ -1,3 +1,4 @@
+#include <cstddef>
 #include "matrix3.h"
 
 namespace zimg {