MT#59962 xmlrpc2di: check XmlRpcSource existence before using

Don't appeal to the XmlRpcSource's members (e.g. `_ssl`)
if this has been freed via `this`.

To check this out see controllable delete behavior
via introduced getter `getsDeletedOnClose()`.

Should fix:

     freed_arg: close frees this.

     CID 542402: (#1 of 1): Read from pointer after free (USE_AFTER_FREE)
     use_after_free: Using freed pointer this.

Change-Id: I8f23564957c57491db8cf051e7296671bf2a698a

apps/xmlrpc2di/xmlrpc++/src/XmlRpcClient.cpp

@@ -143,8 +143,12 @@ XmlRpcClient::close()
     SSL_shutdown(_ssl_ssl);
     XmlRpcUtil::log(4, "XmlRpcClient::close: after SSL_shutdown");
   }
-  XmlRpcSource::close();
-  if (_ssl) {
+
+  bool source_deleted = XmlRpcSource::getsDeletedOnClose();
+
+  XmlRpcSource::close(); /* potentially removes the owner of _ssl via `this` */
+
+  if (!source_deleted && _ssl) {
     // Post-socket shutdown
     XmlRpcUtil::log(4, "XmlRpcClient::close: before SSL_free(_ssl_ssl)");
     SSL_free(_ssl_ssl);

apps/xmlrpc2di/xmlrpc++/src/XmlRpcSource.cpp

@@ -34,7 +34,7 @@ namespace XmlRpc {
     if (_deleteOnClose) {
       XmlRpcUtil::log(2,"XmlRpcSource::close: deleting this");
       _deleteOnClose = false;
-      delete this;
+      delete this; /* the one who is the last turns off the light */
     }
   }
 

apps/xmlrpc2di/xmlrpc++/src/XmlRpcSource.h

@@ -41,6 +41,8 @@ namespace XmlRpc {
     //! Close the owned fd. If deleteOnClose was specified at construction, the object is deleted.
     virtual void close();
 
+    bool getsDeletedOnClose() { return _deleteOnClose; }
+
     //! Return true to continue monitoring this source
     virtual unsigned handleEvent(unsigned eventType) = 0;