all: Fix usage of ctype functions

ctype functions take int as an argument and expect either unsigned char
(values 0-255) or EOF (-1). So explicitly cast signed and not-specified
char type variables to unsigned char.

libudffs/misc.c

@@ -98,7 +98,7 @@ uint32_t strtou32(const char *str, int base, int *failed)
 	errno = 0;
 	ret = strtoll(str, &endptr, base);
 	/* strto* skips leading whitespaces, so detect them via isspace */
-	*failed = (!*str || isspace(*str) || *endptr || errno || ret < 0 || ret > UINT32_MAX) ? 1 : 0;
+	*failed = (!*str || isspace((unsigned char)*str) || *endptr || errno || ret < 0 || ret > UINT32_MAX) ? 1 : 0;
 	return ret;
 }
 

mkudffs/options.c

@@ -385,7 +385,7 @@ void parse_args(int argc, char *argv[], struct udf_disc *disc, char **device, in
 				}
 				for (i = 0; i < 16; ++i)
 				{
-					if (!isxdigit(optarg[i]) || (!isdigit(optarg[i]) && !islower(optarg[i])))
+					if (!isxdigit((unsigned char)optarg[i]) || (!isdigit((unsigned char)optarg[i]) && !islower((unsigned char)optarg[i])))
 					{
 						fprintf(stderr, "%s: Error: Option --uuid is not in lowercase hexadecimal digit format\n", appname);
 						exit(1);

udflabel/options.c

@@ -130,7 +130,7 @@ static void process_uuid_arg(const char *arg, char *new_uuid)
 
 	for (i = 0; i < 16; ++i)
 	{
-		if (!isxdigit(arg[i]) || (!isdigit(arg[i]) && !islower(arg[i])))
+		if (!isxdigit((unsigned char)arg[i]) || (!isdigit((unsigned char)arg[i]) && !islower((unsigned char)arg[i])))
 		{
 			fprintf(stderr, "%s: Error: Option --uuid is not in lowercase hexadecimal digit format\n", appname);
 			exit(1);