Properly handle NULL values for oldOSHandler

omrsig_set_single_async_signal_handler and omrsig_register_os_handler
have been updated to properly handle NULL values for oldOSHandler.
Function description has been updated for both of them. A trace point
was accessing oldOSHandler without a NULL check. A NULL check has been
added before the trace point accesses oldOSHandler.

Signed-off-by: Babneet Singh <sbabneet@ca.ibm.com>

port/common/omrsignal.c

@@ -180,8 +180,12 @@ omrsig_set_async_signal_handler(struct OMRPortLibrary *portLibrary, omrsig_handl
  * entry corresponding to omrsig_handler_fn is removed, and related resources are freed. portlibSignalFlag can only
  * have one signal flag set; otherwise, OMRPORT_SIG_ERROR is returned. One omrsig_handler_fn handler is registered
  * with a signal at any time instead of multiple handlers. When associating a new omrsig_handler_fn with a signal,
- * prior omrsig_handler_fn(s) are dissociated from the signal. The address of the old signal handler function is
- * stored in oldOSHandler. This function supports all signals listed in OMRPORT_SIG_FLAG_SIGALLASYNC.
+ * prior omrsig_handler_fn(s) are dissociated from the signal. This function supports all signals listed in
+ * OMRPORT_SIG_FLAG_SIGALLASYNC.
+ *
+ * The address of the old signal handler function is stored in *oldOSHandler. In case of error, *oldOSHandler will
+ * not be updated. If NULL is provided for oldOSHandler, then *oldOSHandler will not be updated to reflect the old
+ * signal handler function.
  *
  * @param[in] portLibrary The port library
  * @param[in] handler the function to call if an asynchronous signal arrives
@@ -228,8 +232,11 @@ omrsig_map_portlib_signal_to_os_signal(struct OMRPortLibrary *portLibrary, uint3
 /**
  * @brief Register a handler with the OS. For an invalid portlibSignalFlag, an error is returned.
  * portlibSignalFlag is invalid if it is zero or if multiple signal bits are specified. If
- * OS fails to register newOSHandler for the specified signal, then an error is returned. In
- * error cases, oldOSHandler won't be updated.
+ * OS fails to register newOSHandler for the specified signal, then an error is returned.
+ *
+ * The address of the old signal handler function is stored in *oldOSHandler. In case of error,
+ * *oldOSHandler will not be updated. If NULL is provided for oldOSHandler, then *oldOSHandler
+ * will not be updated to reflect the old signal handler function.
  *
  * This function may override a master handler which was previously set by omrsig_protect or
  * omrsig_set_*_async_signal_handler variant. The records associated with the master handler

port/unix/omrsignal.c

@@ -575,7 +575,12 @@ omrsig_set_single_async_signal_handler(struct OMRPortLibrary *portLibrary, omrsi
 
 	omrthread_monitor_exit(asyncMonitor);
 
-	Trc_PRT_signal_omrsig_set_single_async_signal_handler_exiting(rc, handler, handler_arg, portlibSignalFlag, *oldOSHandler);
+	if (NULL != oldOSHandler) {
+		Trc_PRT_signal_omrsig_set_single_async_signal_handler_exiting(rc, handler, handler_arg, portlibSignalFlag, *oldOSHandler);
+	} else {
+		Trc_PRT_signal_omrsig_set_single_async_signal_handler_exiting(rc, handler, handler_arg, portlibSignalFlag, NULL);
+	}
+
 	return rc;
 }
 
@@ -626,7 +631,11 @@ omrsig_register_os_handler(struct OMRPortLibrary *portLibrary, uint32_t portlibS
 		omrthread_monitor_exit(registerHandlerMonitor);
 	}
 
-	Trc_PRT_signal_omrsig_register_os_handler_exiting(rc, portlibSignalFlag, newOSHandler, *oldOSHandler);
+	if (NULL != oldOSHandler) {
+		Trc_PRT_signal_omrsig_register_os_handler_exiting(rc, portlibSignalFlag, newOSHandler, *oldOSHandler);
+	} else {
+		Trc_PRT_signal_omrsig_register_os_handler_exiting(rc, portlibSignalFlag, newOSHandler, NULL);
+	}
 
 	return rc;
 }