In MPI-1.1, it is explicitly stated that an implementation is allowed to require that the arguments argc and argv passed by an application to MPI_INIT in C be the same arguments passed into the application as the arguments to main. In MPI-2 implementations are not allowed to impose this requirement. Conforming implementations of MPI are required to allow applications to pass NULL for both the argc and argv arguments of main. In C++, there is an alternative binding for MPI::Init that does not have these arguments at all.
In some applications, libraries may be making the call to MPI_Init,
and may not have access to argc and argv from main.
It is anticipated that applications requiring special information about
the environment or information supplied by mpiexec can get that
information from environment variables.
( End of rationale.)