lib: Fix sbi_strchr to correctly handle null terminator search

The original sbi_strchr implementation did not conform to the C standard
behavior. According to the C standard and POSIX specification, strchr(s, 0)
should return a pointer to the null terminator at the end of string s.

The previous implementation used a while loop that would terminate when
either reaching the end of string or finding the character, but it would
return NULL when searching for the null terminator instead of returning
a pointer to the null terminator itself.

The fixed implementation uses a do-while loop that ensures even when
searching for the null terminator, the function correctly returns a
pointer to the null terminator position rather than NULL.

This fix ensures sbi_strchr behavior aligns with standard library
function semantics, making it more predictable and safe for users
expecting standard C library behavior.

Signed-off-by: Chen Pei <cp0613@linux.alibaba.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20260306094425.1918-3-cp0613@linux.alibaba.com
Signed-off-by: Anup Patel <anup@brainfault.org>

1 files changed, 5 insertions, 6 deletions

diff --git a/lib/sbi/sbi_string.c b/lib/sbi/sbi_string.c
index f4f13942..3a10c254 100644
--- a/lib/sbi/sbi_string.c
+++ b/lib/sbi/sbi_string.c
@@ -88,13 +88,12 @@ char *sbi_strncpy(char *dest, const char *src, size_t count)
 
 char *sbi_strchr(const char *s, int c)
 {
-	while (*s != '\0' && *s != (char)c)
-		s++;
+	do {
+		if (*s == (char)c)
+			return (char *)s;
+	} while (*s++ != '\0');
 
-	if (*s == '\0')
-		return NULL;
-	else
-		return (char *)s;
+	return NULL;
 }
 
 char *sbi_strrchr(const char *s, int c)