#include <setjmp.h>

jmp_buf ctxt[2];
int cur_ctxt = 0;

void next_context();

main()
{
	context(0);
	context(1);

	next_context();
}


void
next_context()
{
	cur_ctxt = (cur_ctxt + 1) % 2;	
	longjmp(ctxt[cur_ctxt], 1);
}


context(int c)
{
	if (setjmp(ctxt[c]) == 0)
		return;

	while (1) {
		printf("in context %d\n", c);
		next_context();
	}
		
}