Using IA32/AMD64 Alignment Check-bit to error on unaligned access

unalignsignal.c

/*
  Code not originally by me.
  OS must allow changing the status bit (linux does so far)
*/
#include <stdlib.h>

int main(int argc, char **argv)
{
	int *iptr;
	char *cptr;

#if 1
#if defined(__GNUC__)
# if defined(__i386__)
	/* Enable Alignment Checking on x86 */
	__asm__("pushf\norl $0x40000,(%esp)\npopf");
# elif defined(__x86_64__) 
	/* Enable Alignment Checking on x86_64 */
	__asm__("pushf\norl $0x40000,(%rsp)\npopf");
# endif
#endif
#endif

	/* malloc() always provides aligned memory */
	cptr = malloc(sizeof(int) + 1);
	/* Increment the pointer by one, making it misaligned */
	iptr = (int *) ++cptr;
	/* Dereference it as an int pointer, causing an unaligned access */
	*iptr = 42;

	return 0;
}

Would be nicer if you could make that into a function inside a .h file...