Return Code on failure. Positive or negative?

Question

a C-programm can fail to execute under special circumstances in Linux. Example: You allocate some space and the OS denies it.

char *buffer = (char *) malloc         


        

Answer 1

5.1.2.2.3 Program termination

If the return type of the main function is a type compatible with int, a return from the initial call to the main function is equivalent to calling the exit function with the value returned by the main function as its argument; 11) reaching the } that terminates the main function returns a value of 0. If the return type is not compatible with int, the termination status returned to the host environment is unspecified.

7.22.4.4 The exit function:

Finally, control is returned to the host environment. If the value of status is zero or EXIT_SUCCESS, an implementation-defined form of the status successful termination is returned. If the value of status is EXIT_FAILURE, an implementation-defined form of the status unsuccessful termination is returned. Otherwise the status returned is implementation-defined.

I found this to be self-descriptive.