|LONGJMP(3P)||POSIX Programmer's Manual||LONGJMP(3P)|
void longjmp(jmp_buf env, int val);
The longjmp() function shall restore the environment saved by the most recent invocation of setjmp() in the same process, with the corresponding jmp_buf argument. If the most recent invocation of setjmp() with the corresponding jmp_buf occurred in another thread, or if there is no such invocation, or if the function containing the invocation of setjmp() has terminated execution in the interim, or if the invocation of setjmp() was within the scope of an identifier with variably modified type and execution has left that scope in the interim, the behavior is undefined. It is unspecified whether longjmp() restores the signal mask, leaves the signal mask unchanged, or restores it to its value at the time setjmp() was called.
All accessible objects have values, and all other components of the abstract machine have state (for example, floating-point status flags and open files), as of the time longjmp() was called, except that the values of objects of automatic storage duration are unspecified if they meet all the following conditions:
- They are local to the function containing the corresponding setjmp() invocation.
- They do not have volatile-qualified type.
- They are changed between the setjmp() invocation and longjmp() call.
Although longjmp() is an async-signal-safe function, if it is invoked from a signal handler which interrupted a non-async-signal-safe function or equivalent (such as the processing equivalent to exit() performed after a return from the initial call to main()), the behavior of any subsequent call to a non-async-signal-safe function or equivalent is undefined.
The effect of a call to longjmp() where initialization of the jmp_buf structure was not performed in the calling thread is undefined.
The following sections are informative.
It is recommended that applications do not call longjmp() or siglongjmp() from signal handlers. To avoid undefined behavior when calling these functions from a signal handler, the application needs to ensure one of the following two things:
- After the call to longjmp() or siglongjmp() the process only calls async-signal-safe functions and does not return from the initial call to main().
- Any signal whose handler calls longjmp() or siglongjmp() is blocked during every call to a non-async-signal-safe function, and no such calls are made after returning from the initial call to main().
The Base Definitions volume of POSIX.1‐2017, <setjmp.h>
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|2017||IEEE/The Open Group|