MDEV-16478: mysql_real_connect() from libmariadbd.so always crash

Returned accidentally removed undefinition of MYSQL_SERVER in net_serv.cc inside embedded server
(embedded server uses real_net_read/write only as a client)

Prevented attempt to clean up embedded server if it was not initialized

5 files changed, 118 insertions, 4 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 76b0817f8c7..d1595aa77b4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -398,6 +398,7 @@ IF(NOT WITHOUT_SERVER)
   IF(WITH_EMBEDDED_SERVER) 
    ADD_SUBDIRECTORY(libmysqld)
    ADD_SUBDIRECTORY(libmysqld/examples)
+   ADD_SUBDIRECTORY(unittest/embedded)
   ENDIF(WITH_EMBEDDED_SERVER)
 
   IF(WITH_WSREP)
diff --git a/libmysqld/lib_sql.cc b/libmysqld/lib_sql.cc
index d32a96255b9..dd111d1b224 100644
--- a/libmysqld/lib_sql.cc
+++ b/libmysqld/lib_sql.cc
@@ -55,6 +55,9 @@ extern "C" void unireg_clear(int exit_code)
   DBUG_VOID_RETURN;
 }
 
+
+static my_bool mysql_embedded_init= 0;
+
 /*
   Wrapper error handler for embedded server to call client/server error 
   handler based on whether thread is in client/server context
@@ -518,6 +521,8 @@ int init_embedded_server(int argc, char **argv, char **groups)
   const char *fake_groups[] = { "server", "embedded", 0 };
   my_bool acl_error;
 
+  DBUG_ASSERT(mysql_embedded_init == 0);
+
   if (my_thread_init())
     return 1;
 
@@ -637,15 +642,19 @@ int init_embedded_server(int argc, char **argv, char **groups)
   }
 
   execute_ddl_log_recovery();
+  mysql_embedded_init= 1;
   return 0;
 }
 
 void end_embedded_server()
 {
-  my_free(copy_arguments_ptr);
-  copy_arguments_ptr=0;
-  clean_up(0);
-  clean_up_mutexes();
+  if (mysql_embedded_init)
+  {
+    my_free(copy_arguments_ptr);
+    copy_arguments_ptr=0;
+    clean_up(0);
+    clean_up_mutexes();
+  }
 }
 
 
diff --git a/sql/net_serv.cc b/sql/net_serv.cc
index 0d3aa12465d..576ef5009b5 100644
--- a/sql/net_serv.cc
+++ b/sql/net_serv.cc
@@ -47,6 +47,12 @@
 #include "probes_mysql.h"
 #include "proxy_protocol.h"
 
+#ifdef EMBEDDED_LIBRARY
+#undef MYSQL_SERVER
+#undef MYSQL_CLIENT
+#define MYSQL_CLIENT
+#endif /*EMBEDDED_LIBRARY */
+
 /*
   to reduce the number of ifdef's in the code
 */
diff --git a/unittest/embedded/CMakeLists.txt b/unittest/embedded/CMakeLists.txt
new file mode 100644
index 00000000000..cf48550c377
--- /dev/null
+++ b/unittest/embedded/CMakeLists.txt
@@ -0,0 +1,20 @@
+
+INCLUDE_DIRECTORIES(${CMAKE_SOURCE_DIR}/include
+                    ${CMAKE_SOURCE_DIR}/libmysqld/include
+                    ${PCRE_INCLUDES}
+                    ${CMAKE_SOURCE_DIR}/sql
+                    ${MY_READLINE_INCLUDE_DIR}
+                    )
+
+
+ADD_DEFINITIONS(-DEMBEDDED_LIBRARY -UMYSQL_CLIENT)
+
+
+MYSQL_ADD_EXECUTABLE(test-connect-t test-connect.cc
+               COMPONENT Test)
+TARGET_LINK_LIBRARIES(test-connect-t mysqlserver )
+MY_ADD_TEST(test-connect)
+
+IF(UNIX)
+SET_TARGET_PROPERTIES(test-connect-t PROPERTIES ENABLE_EXPORTS TRUE)
+ENDIF()
diff --git a/unittest/embedded/test-connect.cc b/unittest/embedded/test-connect.cc
new file mode 100644
index 00000000000..cd122286130
--- /dev/null
+++ b/unittest/embedded/test-connect.cc
@@ -0,0 +1,78 @@
+#include <mysql.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+int get_evar(char **hostname, char **port, char** username, char ** password)
+{
+
+  if (!((*hostname)= getenv("MYSQL_TEST_HOST")))
+    (*hostname)= (char *)"127.0.0.1";
+
+  if (!((*port)= getenv("MASTER_MYPORT")))
+  {
+    if (!((*port)= getenv("MYSQL_TEST_PORT")))
+      return 1;
+  }
+
+  if (!((*username)= getenv("MYSQL_TEST_USER")))
+    (*username)= (char *)"root";
+
+  if (!((*password)= getenv("MYSQL_TEST_PASSWD")))
+    (*password)= (char *)"";
+
+  return 0;
+}
+
+int main(int argc, char *argv[])
+{
+  MYSQL *mysql;
+  char *host;
+  char *user;
+  char *passwd;
+  char *porta;
+  unsigned int port;
+
+  if (get_evar(&host, &porta, &user, &passwd))
+  {
+    printf("set environment variable MASTER_MYPORT\n");
+    return 1;
+  }
+
+  port = atoi(porta);
+
+  mysql_thread_init();
+
+  if (mysql_server_init(-1, NULL, NULL) != 0) {
+    printf("mysql_library_init failed");
+    return 1;
+  }
+
+
+  mysql = mysql_init(NULL);
+
+  if (!mysql) {
+    printf("mysql_init failed");
+    return 1;
+  }
+
+  if (mysql_options(mysql, MYSQL_OPT_USE_REMOTE_CONNECTION, NULL) != 0) {
+    printf("mysql_options MYSQL_OPT_USE_REMOTE_CONNECTION failed: %s\n", mysql_error(mysql));
+    return 1;
+  }
+
+  if (mysql_options(mysql, MYSQL_SET_CHARSET_NAME, "utf8mb4") != 0) {
+    printf("mysql_options MYSQL_SET_CHARSET_NAME utf8mb4 failed: %s\n", mysql_error(mysql));
+    return 1;
+  }
+
+  if (!mysql_real_connect(mysql, host, user, passwd, NULL, port, NULL, CLIENT_FOUND_ROWS | CLIENT_MULTI_RESULTS | CLIENT_REMEMBER_OPTIONS)) {
+    printf("mysql_real_connect failed: %s\n", mysql_error(mysql));
+    return 1;
+  }
+  mysql_close(mysql);
+  mysql_thread_end();
+  mysql_library_end();
+
+  return 0;
+
+}