One suspicion in parallel::detail::handle_exception.

[taeguk]

I have one doubt about parallel::detail::handle_exception.

hpx/hpx/parallel/exception_list.hpp

Lines 26 to 74 in 76f7c3b

	template <typename ExPolicy, typename Result = void>
	struct handle_exception_impl
	{
	typedef Result type;
	HPX_ATTRIBUTE_NORETURN static Result call()
	{
	try {
	throw; //-V667
	}
	catch(std::bad_alloc const& e) {
	throw e;
	}
	catch (hpx::exception_list const& el) {
	throw el;
	}
	catch (...) {
	throw hpx::exception_list(std::current_exception());
	}
	}
	static hpx::future<Result> call(hpx::future<Result> f)
	{
	HPX_ASSERT(f.has_exception());
	// Intel complains if this is not explicitly moved
	return std::move(f);
	}
	static hpx::future<Result> call(std::exception_ptr const& e)
	{
	try {
	std::rethrow_exception(e);
	}
	catch (std::bad_alloc const&) {
	// rethrow bad_alloc
	return hpx::make_exceptional_future<Result>(
	std::current_exception());
	}
	catch (hpx::exception_list const& el) {
	// rethrow exception_list
	return hpx::make_exceptional_future<Result>(el);
	}
	catch (...) {
	// package up everything else as an exception_list
	return hpx::make_exceptional_future<Result>(
	exception_list(e));
	}
	}

Above, the first handle_exception_impl<>::call() in Line 31 just throws exception. But, the second and third one return an exceptional future. As I think, this is strange. It seems inconsistent.

I think that the struct of Line 79 is for parallel algorithm called with execution::task. So, in the struct, call() all both should return hpx::future<Result>. (In other words, should return exceptional future.)
But in case of Line 27, it is different case. So, it should just return Result as I think. (In other words, should just throw exception.)

How do you think about this issue?

[hkaiser]

This looks suspicious, yes. I will try to investigate in more detail over the next days as I have no immediate answer to why we have it this way. Since all tests pass I'd suspect that

• we either don't test all possible exceptional cases and the code is incorrect,
• the code in question above is never called,
• or simply the above code is correct

[hkaiser]

@taeguk has this been fixed by now?

[taeguk]

@hkaiser This has been not fixed by now. I thought that this is still suspicious. And I waited your reply until now.
How we go about this? Fixing this suspicious thing as I suggest? Or what should we do?

[hkaiser]

@taeguk I'd appreciate it for you to come up with a fix for this. Thanks!