getcontext(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(2)							   System Calls 						     getcontext(2)

NAME

       getcontext, setcontext - get and set current user context

SYNOPSIS

       #include <ucontext.h>

       int getcontext(ucontext_t *ucp);

       int setcontext(const ucontext_t *ucp);

DESCRIPTION

       The  getcontext()  function initializes the structure pointed to by ucp to the current user context of the calling process.  The ucontext_t
       type that ucp points to defines the user context and includes the contents of the calling process' machine registers, the signal mask,  and
       the current execution stack.

       The  setcontext()  function restores the user context pointed to by ucp.  A successful call to setcontext() does not return; program execu-
       tion resumes at the point specified by the ucp argument passed to setcontext(). The ucp argument should be created either by a  prior  call
       to  getcontext(),  or by being passed as an argument to a signal handler. If the ucp argument was created with getcontext(), program execu-
       tion continues as if the corresponding call of getcontext() had just returned.  If the ucp argument was created with makecontext(3C),  pro-
       gram  execution continues with the function passed to makecontext(3C). When that function returns, the process continues as if after a call
       to setcontext() with the ucp argument that was input to makecontext(3C). If the ucp argument was passed to a signal handler, program execu-
       tion  continues	with the program instruction following the instruction interrupted by the signal.  If the uc_link member of the ucontext_t
       structure pointed to by the ucp argument is equal to 0, then this context is the main context, and the process will exit when this  context
       returns.  The effects of passing a ucp argument obtained from any other source are unspecified.

RETURN VALUES

       On successful completion, setcontext() does not return and getcontext() returns 0. Otherwise, -1 is returned.

ERRORS

       No errors are defined.

USAGE

       When a signal handler is executed, the current user context is saved and a new context is created.  If the thread leaves the signal handler
       via longjmp(3UCB), then it is unspecified whether the context at the time of the corresponding  setjmp(3UCB)  call  is  restored  and  thus
       whether	future	calls  to  getcontext()  will  provide	an  accurate  representation of the current context, since the context restored by
       longjmp(3UCB) may not contain all the information that setcontext() requires.  Signal handlers should use siglongjmp(3C) instead.

       Portable applications should not modify or access the uc_mcontext member of ucontext_t.	A portable application cannot assume that  context
       includes  any  process-wide  static data, possibly including errno. Users manipulating contexts should take care to handle these explicitly
       when required.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       sigaction(2),  sigaltstack(2),	sigprocmask(2),   bsd_signal(3C),   makecontext(3C),   setjmp(3UCB),   sigsetjmp(3C),	ucontext.h(3HEAD),
       attributes(5), standards(5)

SunOS 5.11							    5 Feb 2001							     getcontext(2)