Don't discard thrown exception

[xxDark]

Attach pending exception as the cause in throwByName if possible. This change makes it easier to debug errors.

[matthiasblaesing]

Sorry for the late review. In general the idea makes sense. I left an inline comment, that shows how a simpler version could look from my POV.

What is crucially missing is a unittest, that verifies that this works. Please add a demonstrator to validate.

[matthiasblaesing]

I think the cases are to complex and can be simplified to:

Suggested change

	if (cls != NULL) { /* Otherwise an exception has already been thrown */
	if (thrown != NULL) {
	/* Attach thrown exception if possible. */
	/* do_throw_clean is an exit path that will delete 'thrown' if we can't do that. */
	jmethodID init = (*env)->GetMethodID(env, cls, "<init>", "(Ljava/lang/String;)V");
	if (init == NULL) {
	goto do_throw_clean;
	}
	jmethodID initCause = (*env)->GetMethodID(env, cls, "initCause", "(Ljava/lang/Throwable;)Ljava/lang/Throwable;");
	if (initCause == NULL) {
	goto do_throw_clean;
	}
	jobject str = (*env)->NewStringUTF(env, msg);
	if (str == NULL) {
	goto do_throw_clean;
	}
	jthrowable t = (jthrowable) (*env)->NewObject(env, cls, init, str);
	(*env)->DeleteLocalRef(env, str);
	if (t == NULL) {
	goto do_throw_clean;
	}
	jobject ret = (*env)->CallObjectMethod(env, t, initCause, thrown);
	if (ret == NULL) {
	goto do_throw_clean;
	}
	(*env)->DeleteLocalRef(env, ret);
	(*env)->Throw(env, t);
	goto clean_cls;
	} else {
	goto do_throw;
	}
	/* Deletes thrown exception reference and clears the exception. */
	do_throw_clean:
	(*env)->DeleteLocalRef(env, thrown);
	(*env)->ExceptionClear(env);
	do_throw:
	(*env)->ThrowNew(env, cls, msg);
	clean_cls:
	/* It's a good practice to clean up the local references. */
	(*env)->DeleteLocalRef(env, cls);
	} else if (thrown != NULL) {
	(*env)->DeleteLocalRef(env, thrown);
	}
	if (cls != NULL) { /* Otherwise an exception has already been thrown */
	jthrowable t = NULL;
	jmethodID init = (*env)->GetMethodID(env, cls, "<init>", "(Ljava/lang/String;)V");
	jobject str = (*env)->NewStringUTF(env, msg);
	if (init != NULL && str != NULL) {
	t = (jthrowable) (*env)->NewObject(env, cls, init, str);
	}
	if (str != NULL) {
	(*env)->DeleteLocalRef(env, str);
	}
	if (thrown != NULL && t != NULL) {
	jmethodID initCause = (*env)->GetMethodID(env, cls, "initCause", "(Ljava/lang/Throwable;)Ljava/lang/Throwable;");
	/* Attach thrown exception if possible. */
	jobject ret = (*env)->CallObjectMethod(env, t, initCause, thrown);
	(*env)->DeleteLocalRef(env, ret);
	}
	(*env)->Throw(env, t);
	(*env)->DeleteLocalRef(env, cls);
	}
	if (thrown != NULL) {
	(*env)->DeleteLocalRef(env, thrown);
	}