ext/pgsql: Fix warning not being emittedd when failure to cancel a query

Author: Girgias

NEWS

@@ -12,6 +12,10 @@ PHP                                                                        NEWS
   . Add missing filter cleanups on phar failure. (nielsdos)
   . Fixed bug GH-18642 (Signed integer overflow in ext/phar fseek). (nielsdos)
 
+- PGSQL:
+  . Fix warning not being emitted when failure to cancel a query with
+    pg_cancel_query(). (Girgias)
+
 - Readline:
   . Fix memory leak when calloc() fails in php_readline_completion_cb().
     (nielsdos)

ext/pgsql/pgsql.c

@@ -3576,8 +3576,14 @@ static void php_pgsql_do_async(INTERNAL_FUNCTION_PARAMETERS, int entry_type)
 			int rc;
 
 			c = PQgetCancel(pgsql);
+			/* PQcancel
+			 * The return value of PQcancel is 1 if the cancel request was successfully dispatched and 0 if not.
+			 * If not, errbuf is filled with an explanatory error message.
+			 * errbuf must be a char array of size errbufsize (the recommended size is 256 bytes).
+			 * https://www.postgresql.org/docs/current/libpq-cancel.html#LIBPQ-PQCANCEL
+			 */
 			RETVAL_LONG((rc = PQcancel(c, err, sizeof(err))));
-			if (rc < 0) {
+			if (rc == 0) {
 				zend_error(E_WARNING, "cannot cancel the query: %s", err);
 			}
 			while ((pgsql_result = PQgetResult(pgsql))) {