MDEV-7397: SIGSEGV on inserting into a key-less table

When wsrep is enabled, an md5 hash of the entire row is calculated
for tables with no PK. It, however segfaulted as the md5 context
object was not properly constructed.

Fixed by ensuring that the YaSSL's context object gets constructed
explicitly at the specified pre-allocated location (placement)
before its used.

Added a test case.

mysql-test/suite/wsrep/r/basic.result

@@ -27,4 +27,21 @@ c1
 4
 5
 DROP TABLE t1;
+#
+# MDEV-7397: SIGSEGV on inserting into a key-less table
+#
+
+# On node_1
+USE test;
+CREATE TABLE t1(c1 INT) ENGINE=INNODB;
+INSERT INTO t1 VALUES (1);
+SELECT * FROM t1;
+c1
+1
+
+# On node_2
+SELECT * FROM test.t1;
+c1
+1
+DROP TABLE t1;
 # End of test

mysql-test/suite/wsrep/t/basic.test

@@ -22,5 +22,27 @@ SELECT * FROM test.t1;
 # Cleanup
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-7397: SIGSEGV on inserting into a key-less table
+--echo #
+
+--echo
+--echo # On node_1
+--connection node_1
+USE test;
+CREATE TABLE t1(c1 INT) ENGINE=INNODB;
+INSERT INTO t1 VALUES (1);
+SELECT * FROM t1;
+
+--echo
+--echo # On node_2
+--connection node_2
+SELECT * FROM test.t1;
+
+--let $galera_diff_statement = SELECT * FROM t1
+--source include/galera_diff.inc
+# Cleanup
+DROP TABLE t1;
+
 --source include/galera_end.inc
 --echo # End of test

mysys_ssl/my_md5.cc

@@ -34,6 +34,7 @@ typedef TaoCrypt::MD5 MD5_CTX;
 
 static void md5_init(MD5_CTX *context)
 {
+  context= new(context) MD5_CTX;
   context->Init();
 }