cosider different size of size_t type on 32bits and 64bits arches

src/window.h

@@ -32,6 +32,12 @@
 #include <vector>
 #include <string>
 
+# if defined(__WORDSIZE) && __WORDSIZE == 64
+# define SIZE_T_FORMAT "%lu"
+#else
+# define SIZE_T_FORMAT "%u"
+#endif
+
 #if defined(__GNUC__) && __GNUC__ >= 3
 # define GNUC_UNUSED __attribute__((unused))
 # define GNUC_PRINTF(a, b) __attribute__((format(printf, a, b)))