The following sample program, foo.c, directly illustrates the effect of the LP64 data model in contrast to the ILP32 data models. The same program can be compiled as either a 32–bit program or a 64–bit program.
#include <stdio.h> int main(int argc, char *argv[]) { (void) printf("char is \t\t%lu bytes\n", sizeof (char)); (void) printf("short is \t%lu bytes\n", sizeof (short)); (void) printf("int is \t\t%lu bytes\n", sizeof (int)); (void) printf("long is \t\t%lu bytes\n", sizeof (long)); (void) printf("long long is \t\t%lu bytes\n", sizeof (long long)); (void) printf("pointer is \t%lu bytes\n", sizeof (void *)); return (0); }
The result of 32–bit compilation is:
% cc -O -o foo32 foo.c % foo32 char is 1 bytes short is 2 bytes int is 4 bytes long is 4 bytes long long is 8 bytes pointer is 4 bytes |
The result of 64–bit compilation is:
% cc -xarch=generic64 -O -o foo64 foo.c % foo64 char is 1 bytes short is 2 bytes int is 4 bytes long is 8 bytes long long is 8 bytes pointer is 8 bytes |
The default compilation environment is designed to maximize portability, that is, to create 32–bit applications.