Question

Say I have the following c code:

typedef struct _test test;

struct _test {
    test*    just_a_test;
    char*    just_a_char;
};

Would the following implementation work?

class test(Structure):
    _fields_ = [
        ('just_a_test', POINTER(test)),
        ('just_a_char', c_char_p),
    ]

I’m just confused regarding the first pointer in the structure.

Answer 1

Your code will not work because at the time it references test, the class hasn’t been created yet.

This exact problem in described in ctypes documentation under 15.17.1.16. Incomplete Types.

The solution is to set _fields_ after creating the class:

class test(Structure):
    pass
test._fields_ = [
    ('just_a_test', POINTER(test)),
    ('just_a_char', c_char_p),
]