segment_open and segment_close were mentioned with incorrect names.
Discussion: https://postgr.es/m/
20200525234944.GA1573@paquier.xyz
* XLogReadRecord or XLogFindNextRecord; it can be passed in as NULL
* otherwise. The WALRead function can be used as a helper to write
* page_read callbacks, but it is not mandatory; callers that use it,
- * must supply open_segment callbacks. The close_segment callback
+ * must supply segment_open callbacks. The segment_close callback
* must always be supplied.
*
* After reading a record with XLogReadRecord(), it's decomposed into