Report all redo log corruption

Amend commit b853b4f
that was reverted in commit 29150e2.

recv_parse_log_recs(): Do check for corrupted redo log or file
system before checking for len==0, but only read *ptr if
it is not past the end of the buffer (end_ptr).

recv_parse_log_rec(): Report incorrect redo log type
in a consistent way with recv_parse_or_apply_log_rec_body().
This is a follow-up to commit f30c5af.

storage/innobase/log/log0recv.cc

@@ -2253,7 +2253,8 @@ recv_parse_log_rec(
 	case MLOG_MULTI_REC_END | MLOG_SINGLE_REC_FLAG:
 	case MLOG_DUMMY_RECORD | MLOG_SINGLE_REC_FLAG:
 	case MLOG_CHECKPOINT | MLOG_SINGLE_REC_FLAG:
-		ib::error() << "Incorrect log record type:" << *ptr;
+		ib::error() << "Incorrect log record type "
+			<< ib::hex(unsigned(*ptr));
 		recv_sys->found_corrupt_log = true;
 		return(0);
 	}
@@ -2422,10 +2423,6 @@ bool recv_parse_log_recs(lsn_t checkpoint_lsn, store_t store, bool apply)
 		len = recv_parse_log_rec(&type, ptr, end_ptr, &space,
 					 &page_no, apply, &body);
 
-		if (len == 0) {
-			return(false);
-		}
-
 		if (recv_sys->found_corrupt_log) {
 			recv_report_corrupt_log(ptr, type, space, page_no);
 			return(true);
@@ -2435,6 +2432,10 @@ bool recv_parse_log_recs(lsn_t checkpoint_lsn, store_t store, bool apply)
 			return(true);
 		}
 
+		if (len == 0) {
+			return(false);
+		}
+
 		new_recovered_lsn = recv_calc_lsn_on_data_add(old_lsn, len);
 
 		if (new_recovered_lsn > recv_sys->scanned_lsn) {
@@ -2558,13 +2559,10 @@ bool recv_parse_log_recs(lsn_t checkpoint_lsn, store_t store, bool apply)
 				&type, ptr, end_ptr, &space, &page_no,
 				false, &body);
 
-			if (len == 0) {
-				return(false);
-			}
-
 			if (recv_sys->found_corrupt_log
 			    || type == MLOG_CHECKPOINT
-			    || (*ptr & MLOG_SINGLE_REC_FLAG)) {
+			    || (ptr != end_ptr
+				&& (*ptr & MLOG_SINGLE_REC_FLAG))) {
 				recv_sys->found_corrupt_log = true;
 				recv_report_corrupt_log(
 					ptr, type, space, page_no);
@@ -2575,6 +2573,10 @@ bool recv_parse_log_recs(lsn_t checkpoint_lsn, store_t store, bool apply)
 				return(true);
 			}
 
+			if (len == 0) {
+				return(false);
+			}
+
 			recv_previous_parsed_rec_type = type;
 			recv_previous_parsed_rec_offset
 				= recv_sys->recovered_offset + total_len;