SETJMP(3-BSD)       RISC/os Reference Manual        SETJMP(3-BSD)



NAME
     setjmp, longjmp - non-local goto

SYNOPSIS
     #include <setjmp.h>

     setjmp(env)
     jmpbuf env;

     longjmp(env, val)
     jmpbuf env;

     setjmp(env)
     jmpbuf env;

     longjmp(env, val)
     jmpbuf env;

DESCRIPTION
     These routines are useful for dealing with errors and inter-
     rupts encountered in a low-level subroutine of a program.

     setjmp saves its stack environment in env for later use by
     longjmp.  It returns value 0.

     longjmp restores the environment saved by the last call of
     setjmp.  It then returns in such a way that execution con-
     tinues as if the call of setjmp had just returned the value
     val to the function that invoked setjmp, which must not
     itself have returned in the interim.  All accessible data
     have values as of the time longjmp was called.

     setjmp and longjmp save and restore the signal mask sigset-
     mask(2), while setjmp and longjmp manipulate only the C
     stack and registers.

ERRORS
     If the contents of the jmp_buf are corrupted, or correspond
     to an environment that has already returned, longjmp calls
     the routine longjmperror.  If longjmperror returns the pro-
     gram is aborted.  The default version of longjmperror prints
     the message ``longjmp botch'' to standard error and returns.
     User programs wishing to exit more gracefully can write
     their own versions of longjmperror.

SEE ALSO
     sigvec(2), sigstack(2), signal(3)

BUGS
     The System V version of longjmp() will turn a return value
     of 0 into a 1, whereas the BSD version always returns the
     value requested.  A number of programs in BSD systems rely



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SETJMP(3-BSD)       RISC/os Reference Manual        SETJMP(3-BSD)



     on the current behavior.






















































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