typedef pointer const weirdness

Question

please consider the following code:

typedef struct Person* PersonRef; struct Person {   int age; };  const PersonRef person = NULL;  void changePerson(PersonRef newPerson) {   person = newPerson; } 

For some reason, the compiler is complaining about read-only value not assignable. But the const keyword should not make the pointer const. Any ideas?

Answer 1

Note that

typedef int* intptr; const intptr x; 

is not the same as:

const int* x; 

intptr is pointer to int. const intptr is constant pointer to int, not pointer to constant int.

so, after a typedef pointer, i can't make it const to the content anymore?

There are some ugly ways, such as gcc's typeof macro:

typedef int* intptr; intptr dummy; const typeof(*dummy) *x; 

but, as you see, it's pointless if you know the type behind intptr.

Answer 2

const PersonRef person = NULL; 

is

struct Person*const person= NULL; 

so you are consting the pointer and not the object.