Handle incomplete result set metadata more gracefully

Rather than segfaulting because sname is missing lateron, report
a FAIL here. As this indicates a server bug, the errors is reported
as an out of band warning, rather than a client error.

This fixes the PHP side of bug #80713.

Author: nikic

NEWS

@@ -2,6 +2,9 @@ PHP                                                                        NEWS
 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 ?? ??? 2021, php 7.4.17
 
+- MySQLnd:
+  . Fixed bug #80713 (SegFault when disabling ATTR_EMULATE_PREPARES and
+    MySQL 8.0). (Nikita)
 
 04 Mar 2021, php 7.4.16
 

ext/mysqlnd/mysqlnd_wireprotocol.c

@@ -1216,8 +1216,9 @@ php_mysqlnd_rset_field_read(MYSQLND_CONN_DATA * conn, void * _packet)
 		DBG_RETURN(PASS);
 	} else if (EODATA_MARKER == *p && packet->header.size < 8) {
 		/* Premature EOF. That should be COM_FIELD_LIST. But we don't support COM_FIELD_LIST anymore, thus this should not happen */
-		DBG_INF("Premature EOF. That should be COM_FIELD_LIST");
-		DBG_RETURN(PASS);
+		DBG_ERR("Premature EOF. That should be COM_FIELD_LIST");
+		php_error_docref(NULL, E_WARNING, "Premature EOF in result field metadata");
+		DBG_RETURN(FAIL);
 	}
 
 	meta = packet->metadata;