Error: expression must be a pointer to a complete object type (?)

Question

This is the function in C that I need to modify. I am trying to have PREVIOUS 4 bytes of address starting from \"box\" to compare with a returned U32 value from rt_tsk

Answer 1

You're trying to dereference a void *. That won't work. Try this instead:

if (*(((uint32_t *)box)-1) != rt_tsk_self()) {