PBCKP-2705: Adjust signal handling and compatibility for PostgreSQL 18

    This patch adds compatibility changes for PostgreSQL 18:

    - Updated signal handler initialization in pgut.c to use sigaction()
      instead of pqsignal(), as pqsignal() now returns void.
    - Updated process_block_change() in backup.c to handle the new
      RelPathStr structure returned by relpathperm() in v18.
    - Updated CreateReplicationSlot_compat() in stream.c to support the
      new CreateReplicationSlot() signature introduced in v18.

    These changes ensure successful build and runtime behavior with
    PostgreSQL 18 while preserving backward compatibility with earlier
    versions.

Author: dlepikhova

src/backup.c

@@ -2518,11 +2518,16 @@ process_block_change(ForkNumber forknum, RelFileNode rnode, BlockNumber blkno)
 	int			segno;
 	pgFile	  **file_item;
 	pgFile		f;
+#if PG_VERSION_NUM >= 180000
+		RelPathStr rel_path_str = relpathperm(rnode, forknum);
+		rel_path = rel_path_str.str;
+#else
+		rel_path = relpathperm(rnode, forknum);
+#endif
 
 	segno = blkno / RELSEG_SIZE;
 	blkno_inseg = blkno % RELSEG_SIZE;
 
-	rel_path = relpathperm(rnode, forknum);
 	if (segno > 0)
 		f.rel_path = psprintf("%s.%u", rel_path, segno);
 	else
@@ -2554,7 +2559,9 @@ process_block_change(ForkNumber forknum, RelFileNode rnode, BlockNumber blkno)
 
 	if (segno > 0)
 		pg_free(f.rel_path);
+#if PG_VERSION_NUM < 180000
 	pg_free(rel_path);
+#endif
 
 }
 

src/stream.c

@@ -188,7 +188,11 @@ CreateReplicationSlot_compat(PGconn *conn, const char *slot_name, const char *pl
                                           bool is_temporary, bool is_physical,
                                           bool slot_exists_ok)
 {
-#if PG_VERSION_NUM >= 150000
+#if PG_VERSION_NUM >= 180000
+       return CreateReplicationSlot(conn, slot_name, plugin, is_temporary, is_physical,
+               /* reserve_wal = */ true, slot_exists_ok, /* two_phase = */ false, /* failover = */ false);
+#elif PG_VERSION_NUM >= 150000
+
 	return CreateReplicationSlot(conn, slot_name, plugin, is_temporary, is_physical,
 		/* reserve_wal = */ true, slot_exists_ok, /* two_phase = */ false);
 #elif PG_VERSION_NUM >= 110000

src/utils/pgut.c

@@ -1062,7 +1062,23 @@ handle_interrupt(SIGNAL_ARGS)
 static void
 init_cancel_handler(void)
 {
+#if PG_VERSION_NUM < 180000
 	oldhandler = pqsignal(SIGINT, handle_interrupt);
+#else
+	{
+		struct sigaction act, oldact;
+
+		act.sa_handler = handle_interrupt;
+		sigemptyset(&act.sa_mask);
+		act.sa_flags = SA_RESTART;
+
+		/* Get the previous handler and set the new one */
+		if (sigaction(SIGINT, &act, &oldact) < 0)
+		elog(ERROR, "sigaction(SIGINT) failed: %m");
+
+		oldhandler = oldact.sa_handler;
+	}
+#endif
 	pqsignal(SIGQUIT, handle_interrupt);
 	pqsignal(SIGTERM, handle_interrupt);
 	pqsignal(SIGPIPE, handle_interrupt);