https://aur.archlinux.org/cgit/aur.git/commit/iscan-2.30.4.2-c99.patch?h=iscan&id=32ff91a61c0d1eb7a0a3a757cfaaa2034dd48dc1

--- a/backend/defines.h	2021-01-04 08:13:48.995137756 -0000
+++ b/backend/defines.h	2021-01-04 08:16:00.524563361 -0000
@@ -31,6 +31,13 @@
 
 
 #ifndef __cplusplus
+
+/*  Use the C99 bool type if available
+ */
+#ifdef HAVE_STDBOOL_H
+#include <stdbool.h>
+#else
+
 /*! A C++ Boolean type and corresponding keywords for our C code.
  */
 typedef enum {
@@ -38,6 +45,7 @@
   true
 } bool;
 #endif
+#endif
 
 
 /*  Run-time contract validation.
