Split up pgfdw_report_error so that we can mark it pg_noreturn.

pgfdw_report_error has the same design fault as elog/ereport
do, namely that it might or might not return depending on elevel.
While those functions are too widely used to redesign, there are
only about 30 call sites for pgfdw_report_error, and it's not
exposed for extension use.  So let's rethink it.  Split it into
pgfdw_report_error() which hard-wires ERROR elevel and is marked
pg_noreturn, and pgfdw_report() which allows only elevels less
than ERROR.  (Thanks to Álvaro Herrera for suggesting this naming.)

The motivation for doing this now is that in the wake of commit
80aa9848b, which removed a bunch of PG_TRYs from postgres_fdw,
we're seeing more thorough flow analysis there from C compilers
and Coverity.  Marking pgfdw_report_error as noreturn where
appropriate should help prevent false-positive complaints.

We could alternatively have invented a macro wrapper similar
to what we use for elog/ereport, but that code is sufficiently
fragile that I didn't find it appetizing to make another copy.
Since 80aa9848b already changed pgfdw_report_error's signature,
this won't make back-patching any harder than it was already.

Author: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/420221.1753714491@sss.pgh.pa.us

1 files changed, 29 insertions, 10 deletions

diff --git a/contrib/postgres_fdw/connection.c b/contrib/postgres_fdw/connection.c
index a33843fcf85..e8148f2c5a2 100644
--- a/contrib/postgres_fdw/connection.c
+++ b/contrib/postgres_fdw/connection.c
@@ -142,6 +142,8 @@ static void do_sql_command_begin(PGconn *conn, const char *sql);
 static void do_sql_command_end(PGconn *conn, const char *sql,
 							   bool consume_input);
 static void begin_remote_xact(ConnCacheEntry *entry);
+static void pgfdw_report_internal(int elevel, PGresult *res, PGconn *conn,
+								  const char *sql);
 static void pgfdw_xact_callback(XactEvent event, void *arg);
 static void pgfdw_subxact_callback(SubXactEvent event,
 								   SubTransactionId mySubid,
@@ -815,7 +817,7 @@ static void
 do_sql_command_begin(PGconn *conn, const char *sql)
 {
 	if (!PQsendQuery(conn, sql))
-		pgfdw_report_error(ERROR, NULL, conn, sql);
+		pgfdw_report_error(NULL, conn, sql);
 }
 
 static void
@@ -830,10 +832,10 @@ do_sql_command_end(PGconn *conn, const char *sql, bool consume_input)
 	 * would be large compared to the overhead of PQconsumeInput.)
 	 */
 	if (consume_input && !PQconsumeInput(conn))
-		pgfdw_report_error(ERROR, NULL, conn, sql);
+		pgfdw_report_error(NULL, conn, sql);
 	res = pgfdw_get_result(conn);
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
-		pgfdw_report_error(ERROR, res, conn, sql);
+		pgfdw_report_error(res, conn, sql);
 	PQclear(res);
 }
 
@@ -966,7 +968,10 @@ pgfdw_get_result(PGconn *conn)
 /*
  * Report an error we got from the remote server.
  *
- * elevel: error level to use (typically ERROR, but might be less)
+ * Callers should use pgfdw_report_error() to throw an error, or use
+ * pgfdw_report() for lesser message levels.  (We make this distinction
+ * so that pgfdw_report_error() can be marked noreturn.)
+ *
  * res: PGresult containing the error (might be NULL)
  * conn: connection we did the query on
  * sql: NULL, or text of remote command we tried to execute
@@ -979,8 +984,22 @@ pgfdw_get_result(PGconn *conn)
  * marked with have_error = true.
  */
 void
-pgfdw_report_error(int elevel, PGresult *res, PGconn *conn,
-				   const char *sql)
+pgfdw_report_error(PGresult *res, PGconn *conn, const char *sql)
+{
+	pgfdw_report_internal(ERROR, res, conn, sql);
+	pg_unreachable();
+}
+
+void
+pgfdw_report(int elevel, PGresult *res, PGconn *conn, const char *sql)
+{
+	Assert(elevel < ERROR);		/* use pgfdw_report_error for that */
+	pgfdw_report_internal(elevel, res, conn, sql);
+}
+
+static void
+pgfdw_report_internal(int elevel, PGresult *res, PGconn *conn,
+					  const char *sql)
 {
 	char	   *diag_sqlstate = PQresultErrorField(res, PG_DIAG_SQLSTATE);
 	char	   *message_primary = PQresultErrorField(res, PG_DIAG_MESSAGE_PRIMARY);
@@ -1538,7 +1557,7 @@ pgfdw_exec_cleanup_query_begin(PGconn *conn, const char *query)
 	 */
 	if (!PQsendQuery(conn, query))
 	{
-		pgfdw_report_error(WARNING, NULL, conn, query);
+		pgfdw_report(WARNING, NULL, conn, query);
 		return false;
 	}
 
@@ -1563,7 +1582,7 @@ pgfdw_exec_cleanup_query_end(PGconn *conn, const char *query,
 	 */
 	if (consume_input && !PQconsumeInput(conn))
 	{
-		pgfdw_report_error(WARNING, NULL, conn, query);
+		pgfdw_report(WARNING, NULL, conn, query);
 		return false;
 	}
 
@@ -1575,7 +1594,7 @@ pgfdw_exec_cleanup_query_end(PGconn *conn, const char *query,
 					(errmsg("could not get query result due to timeout"),
 					 errcontext("remote SQL command: %s", query)));
 		else
-			pgfdw_report_error(WARNING, NULL, conn, query);
+			pgfdw_report(WARNING, NULL, conn, query);
 
 		return false;
 	}
@@ -1583,7 +1602,7 @@ pgfdw_exec_cleanup_query_end(PGconn *conn, const char *query,
 	/* Issue a warning if not successful. */
 	if (PQresultStatus(result) != PGRES_COMMAND_OK)
 	{
-		pgfdw_report_error(WARNING, result, conn, query);
+		pgfdw_report(WARNING, result, conn, query);
 		return ignore_errors;
 	}
 	PQclear(result);