C++: How can I return a negative value in main.cpp

Question

As an assignment in school, we have to write a C++ program and returns different error codes in the main.

The problem is that we have to return -2

Answer 1

From C++11 standard 18.5/8:

If status is zero or EXIT_SUCCESS, an implementation-defined form of the status successful termination is returned. If status is EXIT_FAILURE, an implementation-defined form of the status unsuccessful termination is returned. Otherwise the status returned is implementation-defined.

Thus is it completely compliant that you get different results for different platforms, and/or compilers.