--- src/doodle/tree.c	2021-04-09 04:27:38.000000000 +0800
+++ src/doodle/tree.c	2025-03-30 02:25:49.000000000 +0800
@@ -147,6 +147,11 @@
 #define DEBUG_READ 0
 #define DEBUG_WRITE 0
 
+/* The symbol exists but not exposed in headers. */
+#ifdef __APPLE__
+extern int fdatasync(int);
+#endif
+
 typedef char * pchar;