Remove redundant null pointer checks before PQclear and PQconninfoFree

These functions already had the free()-like behavior of handling null
pointers as a no-op.  But it wasn't documented, so add it explicitly
to the documentation, too.

Discussion: https://www.postgresql.org/message-id/flat/dac5d2d0-98f5-94d9-8e69-46da2413593d%40enterprisedb.com

contrib/dblink/dblink.c

@@ -157,7 +157,6 @@ dblink_res_internalerror(PGconn *conn, PGresult *res, const char *p2)
 {
 	char	   *msg = pchomp(PQerrorMessage(conn));
 
-	if (res)
 	PQclear(res);
 	elog(ERROR, "%s: %s", p2, msg);
 }
@@ -2756,7 +2755,6 @@ dblink_res_error(PGconn *conn, const char *conname, PGresult *res,
 	 * leaking all the strings too, but those are in palloc'd memory that will
 	 * get cleaned up eventually.
 	 */
-	if (res)
 	PQclear(res);
 
 	/*

contrib/postgres_fdw/postgres_fdw.c

@@ -2790,7 +2790,6 @@ postgresEndDirectModify(ForeignScanState *node)
 		return;
 
 	/* Release PGresult */
-	if (dmstate->result)
 	PQclear(dmstate->result);
 
 	/* Release remote connection */
@@ -3604,7 +3603,6 @@ get_remote_estimate(const char *sql, PGconn *conn,
 	}
 	PG_FINALLY();
 	{
-		if (res)
 		PQclear(res);
 	}
 	PG_END_TRY();
@@ -3853,7 +3851,6 @@ fetch_more_data(ForeignScanState *node)
 	}
 	PG_FINALLY();
 	{
-		if (res)
 		PQclear(res);
 	}
 	PG_END_TRY();
@@ -4338,7 +4335,6 @@ store_returning_result(PgFdwModifyState *fmstate,
 	}
 	PG_CATCH();
 	{
-		if (res)
 		PQclear(res);
 		PG_RE_THROW();
 	}
@@ -4627,7 +4623,6 @@ get_returning_data(ForeignScanState *node)
 		}
 		PG_CATCH();
 		{
-			if (dmstate->result)
 			PQclear(dmstate->result);
 			PG_RE_THROW();
 		}
@@ -4957,7 +4952,6 @@ postgresAnalyzeForeignTable(Relation relation,
 	}
 	PG_FINALLY();
 	{
-		if (res)
 		PQclear(res);
 	}
 	PG_END_TRY();
@@ -5114,7 +5108,6 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel,
 	}
 	PG_CATCH();
 	{
-		if (res)
 		PQclear(res);
 		PG_RE_THROW();
 	}
@@ -5496,7 +5489,6 @@ postgresImportForeignSchema(ImportForeignSchemaStmt *stmt, Oid serverOid)
 	}
 	PG_FINALLY();
 	{
-		if (res)
 		PQclear(res);
 	}
 	PG_END_TRY();

doc/src/sgml/libpq.sgml

@@ -3628,6 +3628,9 @@ char *PQresultErrorField(const PGresult *res, int fieldcode);
 <synopsis>
 void PQclear(PGresult *res);
 </synopsis>
+
+        If the argument is a <symbol>NULL</symbol> pointer, no operation is
+        performed.
        </para>
 
        <para>
@@ -6670,6 +6673,8 @@ void PQfreemem(void *ptr);
 <synopsis>
 void PQconninfoFree(PQconninfoOption *connOptions);
 </synopsis>
+      If the argument is a <symbol>NULL</symbol> pointer, no operation is
+      performed.
      </para>
 
      <para>

src/bin/pg_basebackup/streamutil.c

@@ -197,7 +197,6 @@ GetConnection(void)
 		PQfinish(tmpconn);
 		free(values);
 		free(keywords);
-		if (conn_opts)
 		PQconninfoFree(conn_opts);
 		return NULL;
 	}
@@ -205,7 +204,6 @@ GetConnection(void)
 	/* Connection ok! */
 	free(values);
 	free(keywords);
-	if (conn_opts)
 	PQconninfoFree(conn_opts);
 
 	/*

src/bin/pg_dump/pg_dumpall.c

@@ -1502,7 +1502,6 @@ connectDatabase(const char *dbname, const char *connection_string,
 
 		free(keywords);
 		free(values);
-		if (conn_opts)
 		PQconninfoFree(conn_opts);
 
 		/*

src/bin/psql/command.c

@@ -3476,7 +3476,6 @@ do_connect(enum trivalue reuse_previous_specification,
 
 	/* Release locally allocated data, whether we succeeded or not */
 	pg_free(password);
-	if (cinfo)
 	PQconninfoFree(cinfo);
 
 	if (!success)

src/bin/psql/common.c

@@ -463,7 +463,6 @@ ClearOrSaveResult(PGresult *result)
 		{
 			case PGRES_NONFATAL_ERROR:
 			case PGRES_FATAL_ERROR:
-				if (pset.last_error_result)
 				PQclear(pset.last_error_result);
 				pset.last_error_result = result;
 				break;

src/bin/psql/describe.c

@@ -3492,7 +3492,6 @@ error_return:
 
 	free(view_def);
 
-	if (res)
 	PQclear(res);
 
 	return retval;

src/fe_utils/query_utils.c

@@ -85,7 +85,6 @@ executeMaintenanceCommand(PGconn *conn, const char *query, bool echo)
 
 	r = (res && PQresultStatus(res) == PGRES_COMMAND_OK);
 
-	if (res)
 	PQclear(res);
 
 	return r;

src/interfaces/ecpg/ecpglib/descriptor.c

@@ -923,7 +923,6 @@ ECPGdescribe(int line, int compat, bool input, const char *connection_name, cons
 					if (!ecpg_check_PQresult(res, line, con->connection, compat))
 						break;
 
-					if (desc->result != NULL)
 					PQclear(desc->result);
 
 					desc->result = res;

src/interfaces/ecpg/ecpglib/execute.c

@@ -1714,7 +1714,6 @@ ecpg_process_output(struct statement *stmt, bool clear_result)
 					status = false;
 				else
 				{
-					if (desc->result)
 					PQclear(desc->result);
 					desc->result = stmt->results;
 					clear_result = false;

src/interfaces/libpq/fe-connect.c

@@ -3766,7 +3766,6 @@ keep_going:						/* We will come back to here until there is
 				}
 
 				/* Something went wrong with "SHOW transaction_read_only". */
-				if (res)
 				PQclear(res);
 
 				/* Append error report to conn->errorMessage. */
@@ -3818,7 +3817,6 @@ keep_going:						/* We will come back to here until there is
 				}
 
 				/* Something went wrong with "SELECT pg_is_in_recovery()". */
-				if (res)
 				PQclear(res);
 
 				/* Append error report to conn->errorMessage. */

src/interfaces/libpq/fe-exec.c

@@ -775,11 +775,9 @@ PQclear(PGresult *res)
 void
 pqClearAsyncResult(PGconn *conn)
 {
-	if (conn->result)
 	PQclear(conn->result);
 	conn->result = NULL;
 	conn->error_result = false;
-	if (conn->next_result)
 	PQclear(conn->next_result);
 	conn->next_result = NULL;
 }
@@ -2437,7 +2435,6 @@ PQexecFinish(PGconn *conn)
 	lastResult = NULL;
 	while ((result = PQgetResult(conn)) != NULL)
 	{
-		if (lastResult)
 		PQclear(lastResult);
 		lastResult = result;
 		if (result->resultStatus == PGRES_COPY_IN ||