You can call system();
in any C++ application. On OSX, you can use the open command to launch things as if they were clicked on.
From the documentation for open:
The open command opens a file (or a directory or URL), just as if you had double-clicked the file’s icon. If no application name is specified, the default application as determined via LaunchServices is used to open the specified files.
All together, it would look like:
string command = "open " + filePath;
system(command.c_str());