setcontext(2) - NetBSD Manual Pages

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GETCONTEXT(2)             NetBSD 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.4 UNIX.

NetBSD 10.1                     April 28, 2010                     NetBSD 10.1