NAME
getcontext,
setcontext —
get and set current user
context
LIBRARY
library “libc”
SYNOPSIS
#include
<ucontext.h>
int
getcontext(ucontext_t
*ucp);
int
setcontext(const
ucontext_t *ucp);
DESCRIPTION
Thegetcontext()
function initializes the object pointed to by ucp to the
current user context of the calling thread. The user context defines a
thread's execution environment and includes the contents of its machine
registers, its signal mask, and its current execution stack.
The
setcontext()
function restores the user context defined in the object pointed to by
ucp as most recently initialized by a previous call to
either getcontext() or
makecontext(3). If successful, execution of the program
resumes as defined in the ucp argument, and
setcontext() will not return. If
ucp was initialized by the
getcontext() function, program execution continues
as if the corresponding invocation of getcontext()
had just returned (successfully). If ucp was
initialized by the
makecontext(3) function, program execution continues with the
function (and function arguments) passed to
makecontext(3).
RETURN VALUES
On successful completion, getcontext()
returns 0 and setcontext() does not return.
Otherwise a value of -1 is returned and errno is set
to indicate the error.
ERRORS
The getcontext() and
setcontext() functions will fail if:
- [
EFAULT] - The ucp argument points to an invalid address.
The setcontext() function will fail
if:
- [
EINVAL] - The contents of the datum pointed to by ucp are invalid.
SEE ALSO
sigprocmask(2), longjmp(3), makecontext(3), setjmp(3), swapcontext(3)
STANDARDS
The getcontext() and
setcontext() functions conform to
X/Open System Interfaces and Headers Issue 5
(“XSH5”) and IEEE Std 1003.1-2001
(“POSIX.1”). The errno
indications are an extension to the standard.
The IEEE Std 1003.1-2004
(“POSIX.1”) revision marked the functions
getcontext() and
setcontext() as obsolete, citing portability issues
and recommending the use of POSIX threads instead. The IEEE
Std 1003.1-2008 (“POSIX.1”) revision removed the
functions from the specification.
HISTORY
The getcontext() and
setcontext() functions first appeared in
AT&T System V Release 4 UNIX.