cdef char* cstring = "abcdefg"

cdef void spam(char *target):

    cdef char* s = cstring

    while s[0]:

        target[0] = s[0]

        s += 1

        target += 1

    target[0] = c'\0'

cdef struct Grail:

    char silly[42]

def eggs():

    """

    >>> print(str(eggs()).replace("b'", "'"))

    ('abcdefg', 'abcdefg')

    """

    cdef char[42] silly

    cdef Grail grail

    spam(silly)

    spam(grail.silly)

    return silly, grail.silly