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4.7 Sample 64-Bit From 32-Bit Program
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 -m32 -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 -m64 -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
Note - The default compilation mode depends on the compiler being used. To determine whether your compiler produces 64-bit or 32-bit code by default, refer to the compiler documentation.