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getcontext(3)

NAME

     getcontext, setcontext -- get and set user thread context

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <ucontext.h>

     int
     getcontext(ucontext_t *ucp);

     int
     setcontext(const ucontext_t *ucp);

DESCRIPTION

     The getcontext() function saves the current thread's execution context in
     the structure pointed to by ucp.  This saved context may then later be
     restored by calling setcontext().

     The setcontext() function makes a previously saved thread context the
     current thread context, i.e., the current context is lost and
     setcontext() does not return.  Instead, execution continues in the con-
     text specified by ucp, which must have been previously initialized by a
     call to getcontext(), makecontext(3), or by being passed as an argument
     to a signal handler (see sigaction(2)).

     If ucp was initialized by getcontext(), then execution continues as if
     the original getcontext() call had just returned (again).

     If ucp was initialized by makecontext(3), execution continues with the
     invocation of the function specified to makecontext(3).  When that func-
     tion returns, ucp->uc_link determines what happens next: if ucp->uc_link
     is NULL, the process exits; otherwise, setcontext(ucp->uc_link) is
     implicitly invoked.

     If ucp was initialized by the invocation of a signal handler, execution
     continues at the point the thread was interrupted by the signal.

RETURN VALUES

     If successful, getcontext() returns zero and setcontext() does not
     return; otherwise -1 is returned.

ERRORS

     No errors are defined for getcontext() or setcontext().

SEE ALSO

     sigaction(2), sigaltstack(2), makecontext(3), ucontext(3)

FreeBSD 5.4		      September 10, 2002		   FreeBSD 5.4

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