Question

Is len correctly initialized and safe in set_array call?

void object_copy (Object* self, Object* obj) {
    int len;
    object_set_array (self, object_get_array (obj, &len), len);
}

If not, what would you recommend?

Answer 1

No – there’s no defined order of evaluation for arguments to a function call.

Even though the call to object_get_array() has to occur before the call to object_set_array(), the value that the compiler calculates and passes to object_set_array() for the len parameter can be done before the compiler makes the call to object_get_array().

I’m not sure what the 2nd parameter to the object_set_array() call is intended to be – maybe you wanted to use the comma operator:

void object_foo (Object* self, Object* obj) {
    int len;

    object_set_array (self, (object_get_array (obj, &len), len));
}

Which would work, but is confusing and something I wouldn’t recommend.

I think what you want is:

void object_foo (Object* self, Object* obj) {
    int len;

    object_get_array (obj, &len);  // get the length from obj

    object_set_array (self, len)); // set the len for self
}