Mark `check_al_error()` as `static`
@@ -21,7 +21,7 @@ static unsigned buffer_pos = 0;
// Check if the previous OpenAL call returned an error.
// If an error occurred a message will be logged to stderr.
-bool check_al_error(const char *user_msg, const char *line) {
+static bool check_al_error(const char *user_msg, const char *line) {
ALCenum error = alGetError();
char *description;
