[hackers] [ii] fix undefined behaviour of use of isalpha, isdigit and tolower || Hiltjo Posthuma

[git]

commit 1411224b169b5a2d134111b068e17f3020753ca9
Author:     Hiltjo Posthuma <hil...@codemadness.org>
AuthorDate: Mon Dec 16 18:26:01 2019 +0100
Commit:     Hiltjo Posthuma <hil...@codemadness.org>
CommitDate: Mon Dec 16 18:26:01 2019 +0100

    fix undefined behaviour of use of isalpha, isdigit and tolower
    
    "The argument c must be EOF or representable as an unsigned char;
     otherwise, the result is undefined."

diff --git a/ii.c b/ii.c
index 55d5f52..94da8ab 100644
--- a/ii.c
+++ b/ii.c
@@ -140,9 +140,9 @@ static void
 channel_normalize_path(char *s)
 {
        for (; *s; s++) {
-               if (isalpha(*s))
-                       *s = tolower(*s);
-               else if (!isdigit(*s) && !strchr(".#&+!-", *s))
+               if (isalpha((unsigned char)*s))
+                       *s = tolower((unsigned char)*s);
+               else if (!isdigit((unsigned char)*s) && !strchr(".#&+!-", *s))
                        *s = '_';
        }
 }