Error in string WindowsTcpSocketClient::GetErrorMessage(const int &e)

[VersusQ]

We face to problem with your library.

We builded it with Visual Studio compiler and with definition UNICODE.
The library was builded successfully.

But late we noticed invalid error messages in our log.
Their cause is function WindowsTcpSocketClient::GetErrorMessage().
The function call FormatMessage() and return its result as std::string.
But in our situation FormatMessage() returns utf-16 string and your code casts it to char*.

I suggest you 2 correct cases.
First case returns ANSI string.
Second case returns UTF8 string.
Choose more appropriate case.

// ANSI
std::string WindowsTcpSocketClient::GetErrorMessage(const int &e)
{
	std::string message = "Unknown error";

	const char* lpMsgBuf;
	DWORD dwResult = FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
		FORMAT_MESSAGE_IGNORE_INSERTS,
		NULL, e, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
		(char*)&lpMsgBuf, 0, NULL);

	// if not error
	if (dwResult != 0)
	{
		message = lpMsgBuf;
		LocalFree((HLOCAL)lpMsgBuf);
	}

	return message;
}

// UTF-8
std::string WindowsTcpSocketClient::GetErrorMessage(const int &e)
{
	std::string message = "Unknown error";

	const WCHAR* lpMsgBuf;
	DWORD dwResult = FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
		FORMAT_MESSAGE_IGNORE_INSERTS,
		NULL, e, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
		(WCHAR*)&lpMsgBuf, 0, NULL);

	// if not error
	if (dwResult != 0)
	{
		// convert to utf8
		std::wstring wstr = lpMsgBuf;
		LocalFree((HLOCAL)lpMsgBuf);

		if (!wstr.empty())
		{
			int size_needed = WideCharToMultiByte(CP_UTF8, 0, &wstr[0], (int)wstr.size(), NULL, 0, NULL, NULL);
			std::string u8str(size_needed, 0);
			WideCharToMultiByte(CP_UTF8, 0, &wstr[0], (int)wstr.size(), &u8str[0], size_needed, NULL, NULL);
			message = u8str;
		}
	}

	return message;
}