Silence negative array index warning with toupper

Cast to (unsigned char).

(cherry picked from commit d3f790340e8590ad5da1472c99d25acbc9818496)

diff --git a/lib/isccfg/duration.c b/lib/isccfg/duration.c
index 27dddca1cc2342560be5034486443a475378971f..305047e1af13edc85662732a99ab8413474da1d3 100644 (file)
--- a/lib/isccfg/duration.c
+++ b/lib/isccfg/duration.c
@@ -63,7 +63,7 @@ isccfg_duration_fromtext(isc_textregion_t *source,
        duration->unlimited = false;
 
        /* Every duration starts with 'P' */
-       if (toupper(str[0]) != 'P') {
+       if (toupper((unsigned char)str[0]) != 'P') {
                return (ISC_R_BADNUMBER);
        }
        P = str;