This is in part due to the fact that the bind(c) attribute is part of the Fortran 2003 standard and the snippet is not valid Fortran 2003. The function must be in a module that uses the iso_c_binding module. A valid minimum failing example would be:

module mfe
    use iso_c_binding
    implicit none
contains
    function wat(x, y) result(z) bind(c, name='wat')
        integer(c_int), intent(in) :: x, y
        integer(c_int) :: z
    
        z = x + 7
    end function wat
end module mfe

This compiles happily with gfortran on macOS 10.12.6 However, this still throw an assertion error with NumPy 1.13.3

AssertionError: (1, "x, y@)@ result@(@z@)@ bind@(@c, name='wat'", "x@,@ y@)@ result@(@z@)@ bind@(@c, name='wat'", ')')

I get the same error in both Python 3.6 and 2.7 installed from MacPorts. I cloned the repo and managed to build tags v1.6.0 and v1.7.0 against the native Python (2.7), but I still get the error.

So, is this a user error trying to parse the source using f2py.crackfortran.crackfortran or a parer error as referenced in the closed issue? Are there any other tags where this was to have been fixed?

Update: Fixed the attributes to properly declare the types of the arguments.