ANSI-compatible routines for non-local jumps
| void longjmp (void *j_buf, short ret_val); |
Performs nonlocal goto.
A call to longjmp restores the task state captured by the last call to
setjmp with the argument j_buf. It then
returns in such a way that setjmp appears to have
returned with the value ret_val. j_buf is usually a
buffer of type JMP_BUF. See
setjmp for more info.
Note: longjmp should not be called with a value 0 as ret_val.
| short setjmp (void *j_buf); |
Sets up for nonlocal goto.
setjmp captures the complete task state in j_buf and returns 0.
j_buf is usually a buffer of type JMP_BUF.
A later call to longjmp with j_buf restores
the captured task state and returns in such a way that setjmp appears to have
returned with the value val. A task state consists of address registers A2-A7,
data registers D2-D7, and the program counter.
setjmp must be called before longjmp. The routine that
calls setjmp and sets up j_buf must still be active and cannot have
returned before the longjmp is
called. If it has returned, the results are unpredictable (and usually results
with a crash). setjmp is useful for dealing with errors and exceptions
encountered in a low-level subroutine of a program. setjmp returns 0 when it
is initially called. If the return is from a call to longjmp,
setjmp returns a nonzero value.
Note: The saved task state is not complete enough that setjmp can be used to
implement coroutines (i.e. multitasking). Namely, registers A0, A1, D0, D1 and SR
are not included into the task state.
typedef struct {
|
A type for capturing a task state.
JMP_BUF is a type designed for capturing a task state needed for the setjmp and longjmp commands.