func(va_arg_type, va_arg_type) segfault

[Name Surname]

Is there a reason why this segfaults

    va_start_void(alist);
    myfunction(va_arg_uint(alist), va_arg_ptr(alist, void*));
    va_return_void(alist);

but this does not?

    va_start_void(alist);
    unsigned int i = va_arg_uint(alist);
    void *p        = va_arg_ptr(alist, void*);
    myfunction(i, p);
    va_return_void(alist);

Or is the issue somewhere else in my program?