All rights reserved.
Subject to the following obligations and disclaimer of warranty,
use and redistribution of this software, in source or object code
forms, with or without modifications are expressly permitted by
Packet Design; provided, however, that:
(i) Any and all reproductions of the source or object code
must include the copyright notice above and the following
disclaimer of warranties; and
(ii) No rights are granted, in any manner or form, to use
Packet Design trademarks, including the mark "PACKET DESIGN"
on advertising, endorsements, or otherwise except as such
appears in the above copyright notice or in the software.
THIS SOFTWARE IS BEING PROVIDED BY PACKET DESIGN "AS IS", AND
TO THE MAXIMUM EXTENT PERMITTED BY LAW, PACKET DESIGN MAKES NO
REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING
THIS SOFTWARE, INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
OR NON-INFRINGEMENT. PACKET DESIGN DOES NOT WARRANT, GUARANTEE,
OR MAKE ANY REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS
OF THE USE OF THIS SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY,
RELIABILITY OR OTHERWISE. IN NO EVENT SHALL PACKET DESIGN BE
LIABLE FOR ANY DAMAGES RESULTING FROM OR ARISING OUT OF ANY USE
OF THIS SOFTWARE, INCLUDING WITHOUT LIMITATION, ANY DIRECT,
INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, PUNITIVE, OR CONSEQUENTIAL
DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, LOSS OF
USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
THE USE OF THIS SOFTWARE, EVEN IF PACKET DESIGN IS ADVISED OF
THE POSSIBILITY OF SUCH DAMAGE.
$FreeBSD: head/lib/libc/gen/getcontext.3 248250 2013-03-13 18:18:16Z pluknet $
.Dd March 13, 2013 .Dt GETCONTEXT 3 .Os .Sh NAME .Nm getcontext , getcontextx , setcontext .Nd get and set user thread context .Sh LIBRARY .Lb libc .Sh SYNOPSIS n ucontext.h .Ft int .Fn getcontext "ucontext_t *ucp" .Ft ucontext_t * .Fn getcontextx "void" .Ft int .Fn setcontext "const ucontext_t *ucp" .Sh DESCRIPTION The .Fn getcontext function saves the current thread's execution context in the structure pointed to by .Fa ucp . This saved context may then later be restored by calling .Fn setcontext .
p The .Fn getcontextx function saves the current execution context in the newly allocated structure .Vt ucontext_t , which is returned on success. If architecture defines additional CPU states that can be stored in extended blocks referenced from the .Vt ucontext_t , the memory for them may be allocated and their context also stored. Memory returned by .Fn getcontextx function shall be freed using .Fn free 3 .
p The .Fn setcontext function makes a previously saved thread context the current thread context, i.e., the current context is lost and .Fn setcontext does not return. Instead, execution continues in the context specified by .Fa ucp , which must have been previously initialized by a call to .Fn getcontext , .Xr makecontext 3 , or by being passed as an argument to a signal handler (see .Xr sigaction 2 ) .
p If .Fa ucp was initialized by .Fn getcontext , then execution continues as if the original .Fn getcontext call had just returned (again).
p If .Fa ucp was initialized by .Xr makecontext 3 , execution continues with the invocation of the function specified to .Xr makecontext 3 . When that function returns, .Fa "ucp->uc_link" determines what happens next: if .Fa "ucp->uc_link" is .Dv NULL , the process exits; otherwise, .Fn setcontext "ucp->uc_link" is implicitly invoked.
p If .Fa ucp was initialized by the invocation of a signal handler, execution continues at the point the thread was interrupted by the signal. .Sh RETURN VALUES If successful, .Fn getcontext returns zero and .Fn setcontext does not return; otherwise -1 is returned. The .Fn getcontextx returns pointer to the allocated and initialized context on success, and .Va NULL on failure. .Sh ERRORS No errors are defined for .Fn getcontext or .Fn setcontext . The .Fn getcontextx may return the following errors in .Va errno : l -tag -width Er t Bq Er ENOMEM No memory was available to allocate for the context or some extended state. .El .Sh SEE ALSO .Xr sigaction 2 , .Xr sigaltstack 2 , .Xr makecontext 3 , .Xr ucontext 3