NAME
getcontext,
getcontextx, setcontext
— get and set user thread
context
LIBRARY
library “libc”
SYNOPSIS
#include
<ucontext.h>
int
getcontext(ucontext_t
*ucp);
ucontext_t *
getcontextx(void);
int
setcontext(const
ucontext_t *ucp);
DESCRIPTION
Thegetcontext()
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
getcontextx()
function saves the current execution context in the newly allocated
structure ucontext_t, which is returned on success. If
architecture defines additional CPU states that can be stored in extended
blocks referenced from the ucontext_t, the memory for
them may be allocated and their context also stored. Memory returned by
getcontextx() function shall be freed using
free(3).
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 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 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 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. The getcontextx() returns pointer to the
allocated and initialized context on success, and NULL
on failure.
ERRORS
No errors are defined for getcontext() or
setcontext(). The
getcontextx() may return the following errors in
errno:
- [
ENOMEM] - No memory was available to allocate for the context or some extended state.