setjmp/longjmp if the states were not on the stack. (of course nobody would be so crazy to actually use longjmp, just properly save the stack state: env and con

setjmp/longjmp if the states were not on the stack. (of course nobody would be so crazy to actually use longjmp, just properly save the stack state: env and control) if jumping back into inner states (i.e. out of control stacks), the stack frame needs to be preserved also. as in call/cc later.