common/util: Add casts

When compiling against the standard library, clang complains:

common/util.c:66:6: error: array subscript is of type 'char'
[-Werror,-Wchar-subscripts]
            tolower(*s) == 'f' || tolower(*s) == 'n') {
            ^~~~~~~~~~~

According to POSIX:

The tolower() and tolower_l() functions have as a domain a type int, the
value of which is representable as an unsigned char or the value of EOF.
If the argument has any other value, the behavior is undefined.

https://pubs.opengroup.org/onlinepubs/9699919799/functions/tolower.html

BRANCH=none
BUG=b:234181908
TEST=make utils-str

Signed-off-by: Tom Hughes <tomhughes@chromium.org>
Change-Id: I84f4bfb647f29b24b1c3bd7f5d222275354c4698
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3765458
Reviewed-by: Paul Fagerburg <pfagerburg@chromium.org>

2 files changed, 63 insertions, 2 deletions

diff --git a/common/util.c b/common/util.c
index c911a83ce9..c89770f161 100644
--- a/common/util.c
+++ b/common/util.c
@@ -63,14 +63,16 @@ int parse_bool(const char *s, int *dest)
 {
 	/* off, disable, false, no */
 	if (!strcasecmp(s, "off") || !strncasecmp(s, "dis", 3) ||
-	    tolower(*s) == 'f' || tolower(*s) == 'n') {
+	    tolower((unsigned char)*s) == 'f' ||
+	    tolower((unsigned char)*s) == 'n') {
 		*dest = 0;
 		return 1;
 	}
 
 	/* on, enable, true, yes */
 	if (!strcasecmp(s, "on") || !strncasecmp(s, "ena", 3) ||
-	    tolower(*s) == 't' || tolower(*s) == 'y') {
+	    tolower((unsigned char)*s) == 't' ||
+	    tolower((unsigned char)*s) == 'y') {
 		*dest = 1;
 		return 1;
 	}
diff --git a/test/utils.c b/test/utils.c
index bc78ce8beb..042e3a1ac0 100644
--- a/test/utils.c
+++ b/test/utils.c
@@ -321,6 +321,64 @@ test_static int test_binary_first_base3_from_bits(void)
 	return EC_SUCCESS;
 }
 
+test_static int test_parse_bool(void)
+{
+	int bool_val;
+	int rv;
+
+	/* False cases. */
+
+	bool_val = 1;
+	rv = parse_bool("off", &bool_val);
+	TEST_EQ(rv, 1, "%d");
+	TEST_EQ(bool_val, 0, "%d");
+
+	bool_val = 1;
+	rv = parse_bool("dis", &bool_val);
+	TEST_EQ(rv, 1, "%d");
+	TEST_EQ(bool_val, 0, "%d");
+
+	bool_val = 1;
+	rv = parse_bool("f", &bool_val);
+	TEST_EQ(rv, 1, "%d");
+	TEST_EQ(bool_val, 0, "%d");
+
+	bool_val = 1;
+	rv = parse_bool("n", &bool_val);
+	TEST_EQ(rv, 1, "%d");
+	TEST_EQ(bool_val, 0, "%d");
+
+	/* True cases. */
+
+	bool_val = 0;
+	rv = parse_bool("on", &bool_val);
+	TEST_EQ(rv, 1, "%d");
+	TEST_EQ(bool_val, 1, "%d");
+
+	bool_val = 0;
+	rv = parse_bool("ena", &bool_val);
+	TEST_EQ(rv, 1, "%d");
+	TEST_EQ(bool_val, 1, "%d");
+
+	bool_val = 0;
+	rv = parse_bool("t", &bool_val);
+	TEST_EQ(rv, 1, "%d");
+	TEST_EQ(bool_val, 1, "%d");
+
+	bool_val = 0;
+	rv = parse_bool("y", &bool_val);
+	TEST_EQ(rv, 1, "%d");
+	TEST_EQ(bool_val, 1, "%d");
+
+	/* Error case. */
+	bool_val = -1;
+	rv = parse_bool("a", &bool_val);
+	TEST_EQ(rv, 0, "%d");
+	TEST_EQ(bool_val, -1, "%d");
+
+	return EC_SUCCESS;
+}
+
 void run_test(int argc, char **argv)
 {
 	test_reset();
@@ -339,6 +397,7 @@ void run_test(int argc, char **argv)
 	RUN_TEST(test_safe_memcmp);
 	RUN_TEST(test_alignment_log2);
 	RUN_TEST(test_binary_first_base3_from_bits);
+	RUN_TEST(test_parse_bool);
 
 	test_print_result();
 }