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swapcontext(3)

NAME

     makecontext, swapcontext -- modify and exchange user thread contexts

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <ucontext.h>

     void
     makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...);

     int
     swapcontext(ucontext_t *oucp, const ucontext_t *ucp);

DESCRIPTION

     The makecontext() function modifies the user thread context pointed to by
     ucp, which must have previously been initialized by a call to
     getcontext(3) and had a stack allocated for it.  The context is modified
     so that it will continue execution by invoking func() with the arguments
     provided.	The argc argument must be equal to the number of additional
     arguments provided to makecontext() and also equal to the number of argu-
     ments to func(), or else the behavior is undefined.

     The ucp->uc_link argument must be initialized before calling
     makecontext() and determines the action to take when func() returns: if
     equal to NULL, the process exits; otherwise, setcontext(ucp->uc_link) is
     implicitly invoked.

     The swapcontext() function saves the current thread context in *oucp and
     makes *ucp the currently active context.

RETURN VALUES

     If successful, swapcontext() returns zero; otherwise -1 is returned and
     the global variable errno is set appropriately.

ERRORS

     The swapcontext() function will fail if:

     [ENOMEM]		There is not enough stack space in ucp to complete the
			operation.

SEE ALSO

     setcontext(3), ucontext(3)

FreeBSD 5.4		      September 10, 2002		   FreeBSD 5.4

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