py/qstr: Special case qstr_find_strn for empty string.
This handles the case where an empty bytes/bytearray/str could pass in
NULL as the str argument (with length zero). This would result in UB in
strncmp. Even though our bare-metal implementation of strncmp handles
this, best to avoid it for when we're using system strncmp.
This work was funded through GitHub Sponsors.
Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
diff --git a/py/qstr.c b/py/qstr.c
index 0ae0835..dc89013 100644
--- a/py/qstr.c
+++ b/py/qstr.c
@@ -233,6 +233,11 @@
}
qstr qstr_find_strn(const char *str, size_t str_len) {
+ if (str_len == 0) {
+ // strncmp behaviour is undefined for str==NULL.
+ return MP_QSTR_;
+ }
+
// work out hash of str
size_t str_hash = qstr_compute_hash((const byte *)str, str_len);