use safe_islower to avoid UB

1 files changed, 8 insertions, 0 deletions

diff --git a/common.h b/common.h
index abef5af..ed4b05e 100644
--- a/common.h
+++ b/common.h
@@ -7,6 +7,7 @@
 
 #include <limits.h>
 #include <stddef.h>
+#include <ctype.h>
 
 #include "pack.h"
 
@@ -39,6 +40,13 @@
 	T(LLONG,  signed,   long long, long long) \
 	T(ULLONG, unsigned, long long, long long)
 
+// safe_islower: islower but no domain errors
+static inline int safe_islower(int c)
+{
+	if (c < 0 || c > UCHAR_MAX) return 0;
+	return islower(c);
+}
+
 size_t getsize(enum pack_type t);
 
 #endif // !PACK_COMMON_H