Solaris 64-bit Developer's Guide

Do Not Assume int and Pointers Are the Same Size

Since ints and pointers are the same size in the ILP32 environment, a lot of code relies on this assumption. Pointers are often cast to int or unsigned int for address arithmetic. Instead, pointers could be cast to long because long and pointers are the same size in both ILP32 and LP64 worlds. Rather than explicitly using unsigned long, use uintptr_t because it expresses the intent more closely and makes the code more portable, insulating it against future changes. For example,

char *p;
p = (char *) ((int)p & PAGEOFFSET);

produces the warning:

warning: conversion of pointer loses bits

Using the following code will produce the clean results:

char *p;
p = (char *) ((uintptr_t)p & PAGEOFFSET);