Getting dll path / string issue (C++ beginner)

Question

I have a self registering COM visible dll (C++) installed in a folder in Program Files along with an appref-ms file that points at a click once application. The purpose of this dll is to allow the click once app to be launched from the right click menu in windows explorer.

I am modifying existing code that uses wchar_t* exclusively to hold strings, and I have very limited experience with C++. I am using the following to get the path to the the folder that contains the dll and appref-ms.

std::wstring DllFolder() {
    wchar_t buffer[MAX_PATH];
    GetModuleFileName( (HINSTANCE)&__ImageBase, buffer, MAX_PATH );
    std::wstring::size_type pos = std::wstring( buffer ).find_last_of( L"\\/" );
    return std::wstring( buffer ).substr( 0, pos);
}

...

const wchar_t* folder = DllFolder().c_str();

This almost works, but the drive letter is difference every time. Examples:

{:\Projects\MyAppName\x64\Release e:\Projects\MyAppName\x64\Release O:\Projects\MyAppName\x64\Release

Sometimes there is a new line after the : and no letter.

Another question: I hold the launch string in a class member wchar_t m_Launch[MAX_PATH*10]. Since I don't know how many files the user will select, is there a way to dynamically resize it?

Answer 1

Function DLLFolder() returns temporary object. When you got a pointer to it's data (via folder = DLLFolder().c_str()) you got a pointer to symbol array, that will be destroyed when destructor of wstring will be called (it would be at the next line). The solutions are:

1. Don't get a pointer, but use a copy of wstring:

   std::wstring folder = DLLFolder();

2. Forward pointer to function, that need it, in the same call:

   do_smth_with_dll_folder( DllFolder().c_str() )