You can make a DLL that exports any functions you need, such as _popen and its brethren.

That said, I wouldn't use _popen(). I'd write a DLL that uses Boost Process to launch a child process and Boost Asio to communicate with its stdin & stdout - or perhaps with a pipe.

Or just do the file method. That's the five-minute solution.

EDIT - Honorable mention goes to the Windows API. Some of this stuff is actually included in Zorro's windows.h header.