commit af3bb68add1c40d19d0dee382009e21b0870a38f
from: NRK <nrk@disroot.org>
via: Hiltjo Posthuma <hiltjo@codemadness.org>
date: Fri Mar 18 11:11:27 2022 UTC

avoid potential UB when using isprint()

all the ctype.h functions' argument must be representable as an unsigned
char or as EOF, otherwise the behavior is undefined.

commit - 2aefa348baf4b702fdce98eb105bcba175d8283f
commit + af3bb68add1c40d19d0dee382009e21b0870a38f
blob - c71fa0677ee40d7ba71b5b67fbb70b4386500be8
blob + 1307fdf4ab3afee8d16af827b1a04a99152cf1ec
--- st.c
+++ st.c
@@ -367,7 +367,7 @@ static const char base64_digits[] = {
 char
 base64dec_getc(const char **src)
 {
-	while (**src && !isprint(**src))
+	while (**src && !isprint((unsigned char)**src))
 		(*src)++;
 	return **src ? *((*src)++) : '=';  /* emulate padding if string ends */
 }