--- ./base/fapi_ft.c	2020-09-25 20:31:10.000000000 +0800
+++ ./base/fapi_ft.c	2021-04-29 20:48:03.877882468 +0800
@@ -125,7 +125,7 @@
 delete_inc_int_info(gs_fapi_server * a_server,
                     FT_IncrementalRec * a_inc_int_info);
 
-FT_CALLBACK_DEF(void *)
+static void *
 FF_alloc(FT_Memory memory, long size)
 {
     gs_memory_t *mem = (gs_memory_t *) memory->user;
@@ -133,7 +133,7 @@
     return (gs_malloc(mem, size, 1, "FF_alloc"));
 }
 
-FT_CALLBACK_DEF(void *)
+static void *
     FF_realloc(FT_Memory memory, long cur_size, long new_size, void *block)
 {
     gs_memory_t *mem = (gs_memory_t *) memory->user;
@@ -153,7 +153,7 @@
     return (tmp);
 }
 
-FT_CALLBACK_DEF(void)
+static void
     FF_free(FT_Memory memory, void *block)
 {
     gs_memory_t *mem = (gs_memory_t *) memory->user;