getopt: fix null pointer arithmetic ub

When an option that requires an argument is the last character of
argv[argc-1], getopt computes argv[argc] + optpos. While optpos
is always zero in this case, adding it to null pointer is still
undefined.

diff --git a/src/misc/getopt.c b/src/misc/getopt.c
index c3f6699..b02b81c 100644 (file)
--- a/src/misc/getopt.c
+++ b/src/misc/getopt.c
@@ -87,7 +87,8 @@ int getopt(int argc, char * const argv[], const char *optstring)
        if (optstring[i] == ':') {
                optarg = 0;
                if (optstring[i+1] != ':' || optpos) {
-                       optarg = argv[optind++] + optpos;
+                       optarg = argv[optind++];
+                       if (optpos) optarg += optpos;
                        optpos = 0;
                }
                if (optind > argc) {