Cast a char argument to isspace() to unsigned char.

diff --git a/src/xz/args.c b/src/xz/args.c
index 57f3482..97b2244 100644 (file)
--- a/src/xz/args.c
+++ b/src/xz/args.c
@@ -374,7 +374,14 @@ parse_environment(args_info *args, char *argv0)
        int argc = 1;
        bool prev_was_space = true;
        for (size_t i = 0; env[i] != '\0'; ++i) {
-               if (isspace(env[i])) {
+               // NOTE: Cast to unsigned char is needed so that correct
+               // value gets passed to isspace(), which expects
+               // unsigned char cast to int. Casting to int is done
+               // automatically due to integer promotion, but we need to
+               // force char to unsigned char manually. Otherwise 8-bit
+               // characters would get promoted to wrong value if
+               // char is signed.
+               if (isspace((unsigned char)env[i])) {
                        prev_was_space = true;
                } else if (prev_was_space) {
                        prev_was_space = false;
@@ -399,7 +406,7 @@ parse_environment(args_info *args, char *argv0)
        argc = 1;
        prev_was_space = true;
        for (size_t i = 0; env[i] != '\0'; ++i) {
-               if (isspace(env[i])) {
+               if (isspace((unsigned char)env[i])) {
                        prev_was_space = true;
                        env[i] = '\0';
                } else if (prev_was_space) {