A C++ utility for safe function execution with comprehensive exception handling. Supports both sync and async execution and cross platform compatible

SafeExec.hpp

#pragma once
#include <any>
#include <functional>
#include <optional>
#include <type_traits>
#include <utility>
#include <thread>
#include <future>
#include <iostream>
#include <array>
#include <string>
#if defined(_WIN32)
#include <Windows.h>
#endif

namespace SafeExecutor
{
	static constexpr auto EXCEPTION_CPP_MAGIC = 0xE06D7363;

	template <typename T, size_t N>
	static constexpr auto StackString(const T(&str)[N])
	{
		std::array <T, N> ret{};
		std::copy(std::begin(str), std::end(str), ret.begin());
		return ret;
	}

	// Enum class for possible error codes
	enum class ResultCode : uint8_t
	{
		Success,
		DivisionByZero,
		InvalidArgument,
		OutOfRange,
		LogicError,
		SystemError,
		RuntimeError,
		BadAlloc,
		CppException,
		UnknownException,
		SEHException,
		UnknownResult,
		FutureError
	};
	// Convert result to string
	constexpr const char* ResultCodeToString(ResultCode code)
	{
		switch (code)
		{
		case ResultCode::Success:
			return "Success";
		case ResultCode::DivisionByZero:
			return "DivisionByZero";
		case ResultCode::InvalidArgument:
			return "InvalidArgument";
		case ResultCode::OutOfRange:
			return "OutOfRange";
		case ResultCode::LogicError:
			return "LogicError";
		case ResultCode::SystemError:
			return "SystemError";
		case ResultCode::RuntimeError:
			return "RuntimeError";
		case ResultCode::BadAlloc:
			return "BadAlloc";
		case ResultCode::CppException:
			return "CppException";
		case ResultCode::UnknownException:
			return "UnknownException";
		case ResultCode::SEHException:
			return "SEHException";
		case ResultCode::UnknownResult:
			return "UnknownResult";
		default:
			return "Unknown";
		}
	}

	// Helper type trait to check if a type is void
	template <typename T>
	struct is_void_type : std::is_void<std::remove_cv_t<T>> {};

	// Specialization of TResultOf for void return type
	template <typename Fn, typename... Args>
	using TResultOf = std::conditional_t<
		is_void_type<std::invoke_result_t<Fn, Args...>>::value,
		std::monostate,
		std::invoke_result_t<Fn, Args...>
	>;

	// Handler type of a function
	using TExceptionHandler = std::function<void(uint32_t, const char*)>;
	
	// Execute function as C++ exception protected code inside SEH handler function(execute_seh_safe)
	template <typename Fn, typename... Args>
	std::optional <TResultOf <Fn, Args...>> ExecuteCPPExceptionSafe(const TExceptionHandler& handler, Fn&& fn, Args&&... args) noexcept
	{
		using ResultType = TResultOf <Fn, Args...>;
		try
		{
			if constexpr (std::is_same_v <ResultType, void> || std::is_same_v <ResultType, std::monostate>)
			{
				std::invoke(std::forward<Fn>(fn), std::forward<Args>(args)...);
				return std::nullopt;
			}
			else
			{
				return std::make_optional(std::invoke(std::forward<Fn>(fn), std::forward<Args>(args)...));
			}
		}
		catch (const std::invalid_argument& e)
		{
			handler(static_cast<uint32_t>(ResultCode::InvalidArgument), e.what());
			return std::nullopt;
		}
		catch (const std::out_of_range& e)
		{
			handler(static_cast<uint32_t>(ResultCode::OutOfRange), e.what());
			return std::nullopt;
		}
		catch (const std::logic_error& e)
		{
			handler(static_cast<uint32_t>(ResultCode::LogicError), e.what());
			return std::nullopt;
		}
		catch (const std::system_error& e)
		{
			handler(static_cast<uint32_t>(ResultCode::SystemError), e.what());
			return std::nullopt;
		}
		catch (const std::runtime_error& e)
		{
			handler(static_cast<uint32_t>(ResultCode::RuntimeError), e.what());
			return std::nullopt;
		}
		catch (const std::bad_alloc& e)
		{
			handler(static_cast<uint32_t>(ResultCode::BadAlloc), e.what());
			return std::nullopt;
		}
		catch (const std::exception& e)
		{
			handler(static_cast<uint32_t>(ResultCode::CppException), e.what());
			return std::nullopt;
		}
		catch (...)
		{
			handler(static_cast<uint32_t>(ResultCode::UnknownException), StackString("Unhandled Exception").data());
			return std::nullopt;
		}
		return std::nullopt;
	}

	inline uint32_t SEHExceptionParser(const uint32_t code, const EXCEPTION_POINTERS* pEP)
	{
		// TODO: Give more information about the exception
		return code == EXCEPTION_CPP_MAGIC ? EXCEPTION_CONTINUE_SEARCH : EXCEPTION_EXECUTE_HANDLER;
	}
	
	// Executes the given function and returns the result or an exception
	template <typename Fn, typename... Args>
	inline auto ExecuteSafeEx(TExceptionHandler handler, Fn&& fn, Args&&... args) -> std::pair <std::optional <TResultOf <Fn, Args...>>, ResultCode>
	{
		using ResultType = TResultOf <Fn, Args...>;
		std::pair <std::optional <ResultType>, ResultCode> result;
		
		std::optional <ResultType> optResult;
		auto ExecuteSafeWorkerImpl = [&]() -> void {
			optResult = ExecuteCPPExceptionSafe(handler, std::forward<Fn>(fn), std::forward<Args>(args)...);
		};
		
#ifdef _WIN32
		// HACK: Bypass for 'Cannot use __try in functions that require object unwinding'. 
		auto ExecuteSafeImpl = [&]() {
			__try
			{
				ExecuteSafeWorkerImpl();
				if constexpr (std::is_same_v <ResultType, void> || std::is_same_v <ResultType, std::monostate>)
					result = std::make_pair(optResult, ResultCode::Success);
				else
				{
					if (!optResult)
						result = std::make_pair(std::nullopt, ResultCode::UnknownResult);
					else
						result = std::make_pair(optResult, ResultCode::Success);
				}
			}
			__except (SEHExceptionParser(GetExceptionCode(), GetExceptionInformation()))
			{
				handler(GetExceptionCode(), StackString("SEH Exception").data());
				result = std::make_pair(std::nullopt, ResultCode::SEHException);
			}
		};
		ExecuteSafeImpl();
#else
		ExecuteSafeWorkerImpl();
#endif

		return result;
	}
	template <typename Fn, typename... Args>
	inline auto ExecuteSafe(Fn&& fn, Args&&... args) -> std::pair <std::optional <TResultOf <Fn, Args...>>, ResultCode>
	{
		return ExecuteSafeEx([](uint32_t code, const char* name) -> void {
			std::cout << StackString("Error").data() << name << '(' << code << ')' << std::endl;
		}, std::forward<Fn>(fn), std::forward<Args>(args)...);
	}

	template <typename Fn, typename... Args>
	inline auto ExecuteSafeAsyncEx(TExceptionHandler handler, Fn&& fn, Args&&... args) -> std::future <std::pair <std::optional <TResultOf <Fn, Args...>>, ResultCode>>
	{
		try
		{
			return std::async(std::launch::async, [&]() {
				return ExecuteSafeEx(handler, std::forward<Fn>(fn), std::forward<Args>(args)...);
			});
		}
		catch (const std::future_error&)
		{
			return std::async(std::launch::async, []() -> std::pair <std::optional <TResultOf <Fn, Args...>>, ResultCode> {
				return std::make_pair(std::nullopt, ResultCode::FutureError);
			});
		}
	}
	template <typename Fn, typename... Args>
	inline auto ExecuteSafeAsync(Fn&& fn, Args&&... args) -> std::future <std::pair <std::optional <TResultOf <Fn, Args...>>, ResultCode>>
	{
		return ExecuteSafeAsyncEx([](uint32_t code, const char* name) -> void {
			std::cout << StackString("Future Error").data() << name << '(' << code << ')' << std::endl;
		}, std::forward<Fn>(fn), std::forward<Args>(args)...);
	}
}