diff -aur src.orig/clanlib-1.0~svn3827/Sources/API/Core/System/cl_assert.h src/clanlib-1.0~svn3827/Sources/API/Core/System/cl_assert.h
--- src.orig/clanlib-1.0~svn3827/Sources/API/Core/System/cl_assert.h	2021-06-06 15:17:41.575014216 +0200
+++ src/clanlib-1.0~svn3827/Sources/API/Core/System/cl_assert.h	2021-06-06 15:17:53.545055365 +0200
@@ -29,6 +29,8 @@
 
 //! clanCore="System"
 //! header=core.h
+//
+#include <cstddef>
 
 #ifndef header_cl_assert
 #define header_cl_assert