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SETJMP(3)                BSD Library Functions Manual                SETJMP(3)

NAME
     _longjmp, _setjmp, longjmp, longjmperror, setjmp, siglongjmp, sigsetjmp -- non-local jumps

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <setjmp.h>

     void
     _longjmp(jmp_buf env, int val);

     int
     _setjmp(jmp_buf env);

     void
     longjmp(jmp_buf env, int val);

     void
     longjmperror(void);

     int
     setjmp(jmp_buf env);

     void
     siglongjmp(sigjmp_buf env, int val);

     int
     sigsetjmp(sigjmp_buf env, int savemask);

DESCRIPTION
     The sigsetjmp(), setjmp(), and _setjmp() functions save their calling environment in env.  Each of
     these functions returns 0.

     The corresponding longjmp() functions restore the environment saved by their most recent respective
     invocations of the setjmp() function.  They then return, so that program execution continues as if the
     corresponding invocation of the setjmp() call had just returned the value specified by val, instead of
     0.

     Pairs of calls may be intermixed (i.e., both sigsetjmp() and siglongjmp() and setjmp() and longjmp()
     combinations may be used in the same program); however, individual calls may not (e.g. the env argument
     to setjmp() may not be passed to siglongjmp()).

     The longjmp() routines may not be called after the routine which called the setjmp() routines returns.

     All accessible objects have values as of the time longjmp() routine was called, except that the values
     of objects of automatic storage invocation duration that do not have the volatile type and have been
     changed between the setjmp() invocation and longjmp() call are indeterminate.

     The setjmp()/longjmp() pairs save and restore the signal mask while _setjmp()/_longjmp() pairs save and
     restore only the register set and the stack.  (See sigprocmask(2).)

     The sigsetjmp()/siglongjmp() function pairs save and restore the signal mask if the argument savemask
     is non-zero; otherwise, only the register set and the stack are saved.

ERRORS
     If the contents of the env are corrupted, or correspond to an environment that has already returned,
     the longjmp() routine calls the routine longjmperror(3).  If longjmperror() returns, the program is
     aborted (see abort(3)).  The default version of longjmperror() prints the message ``longjmp botch'' to
     standard error and returns.  User programs wishing to exit more gracefully should write their own ver-sions versions
     sions of longjmperror().

SEE ALSO
     sigaction(2), sigaltstack(2), signal(3)

STANDARDS
     The setjmp() and longjmp() functions conform to ISO/IEC 9899:1990 (``ISO C90'').  The sigsetjmp() and
     siglongjmp() functions conform to IEEE Std 1003.1-1988 (``POSIX.1'').

BSD                              June 4, 1993                              BSD