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 execu

tion 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 context specified by ucp, which must have been previously ini

tialized 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 con

tinues as if
the original getcontext() call had just returned (again).

If ucp was initialized by makecontext(3), execution contin

ues with the
invocation of the function specified to makecontext(3).

When that function 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 han

dler, 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)

BSD September 10, 2002

BSD