Cast 32 bit int to 64 void * pointer without warning

Question

I have a "generic" linked link in C that takes void * data to store the data in a Node.

insertNode(linkedList * list, void *data);

//Storing/retrieving a string works fine;
char *str="test"; 
insertNode(list, str);
char *getback=(char *)node->data;

//Storing/retrieving an Int results a cast warning
int num=1;
insertNode(list,(void *)num);
int getback=(int)node->data;

This is because int is 32 bit, but void * is 64 bit on x64 machine. What is the best practice to get rid of this error?

Answer 1

Use intptr_t or uintptr_t. They are integers of the same size as a pointer:

#include <stdint.h>
...
intptr_t num = 1;
insertNode(list, (void *) num);
intptr_t getback = (intptr_t) node->data;

Of course, the maximum value that you can store depends on the system, but you can examine it at compile time via INTPTR_MIN and INTPTR_MAX.