--- a/debugger/mcs51/sdcdb.h	2024-02-05 02:33:46.000000000 +0800
+++ b/debugger/mcs51/sdcdb.h	2025-05-12 14:33:25.897757364 +0800
@@ -60,7 +60,13 @@
 #define TRUE 1
 #define FALSE !TRUE
 
+#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
+/* C99 + <stdbool.h> is guaranteed to exist */
+#include <stdbool.h>
+#else
+/* very old compilers: fall back to DIY typedef */
 typedef short bool;
+#endif
 
 #ifndef max
 #define max(a,b) (a > b ? a : b)