setcontext(2) [netbsd man page]

GETCONTEXT(2)						      BSD System Calls Manual						     GETCONTEXT(2)

NAME

     getcontext, setcontext -- get and set current user 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 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.

BSD
								  April 28, 2010							       BSD

GETCONTEXT(3)						   BSD Library Functions Manual 					     GETCONTEXT(3)

NAME

     getcontext, getcontextx, setcontext -- get and set user thread context

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <ucontext.h>

     int
     getcontext(ucontext_t *ucp);

     ucontext_t *
     getcontextx(void);

     int
     setcontext(const ucontext_t *ucp);

DESCRIPTION

     The getcontext() 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.

SEE ALSO

     sigaction(2), sigaltstack(2), makecontext(3), ucontext(3)

BSD
								  March 13, 2013							       BSD