IS* macros may not be given arguments with side effects.

diff --git a/src/pr.c b/src/pr.c
index c49819d8063b78529e2533df48c09b5e0fcac1f8..1abb686bbd97ee57ed051ab145687c59189bf259 100644 (file)
--- a/src/pr.c
+++ b/src/pr.c
@@ -455,7 +455,8 @@ main (argc, argv)
          s = optarg;
          if (*s == '+')
            {
-             if (!ISDIGIT (*++s))
+             ++s;
+             if (!ISDIGIT (*s))
                usage ("`+' requires a numeric argument");
              first_page_number = atoi (s);
            }