C++ std::string conversion problem on Windows

Question

This is my procedure:

bool Open(std::string filename)
{
    ...
    HANDLE hFile = CreateFile(filename.c_str(), GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, 0, NULL);
    ...
}

Error:'CreateFileW' : cannot convert parameter 1 from 'const char *' to 'LPCWSTR' Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast

Where is the problem?

Answer 1

A std::string consists of an array of char's, and so the c_str function returns a const char*.

A LPCWSTR is a Long Pointer to a Constant Wide String, or in other words, const wchar_t*.

So you have a couple of options. Either get the filename as a wide string (std::wstring), or specify that you want the non-wide version of CreateFile instead. That can be done either by calling CreateFileA or disabling UNICODE in your project settings.

CreateFile is a macro which either resolves to CreateFileA (the char version) or CreateFileW (the wide char version) depending on whether or not unicode is enabled.