makecontext(3) [osx man page]

MAKECONTEXT(3)						   BSD Library Functions Manual 					    MAKECONTEXT(3)

NAME

     makecontext, swapcontext -- modify and exchange user thread contexts

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <ucontext.h>

     void
     makecontext(ucontext_t *ucp, void (*func)(), int argc, ...);

     int
     swapcontext(ucontext_t *oucp, const ucontext_t *ucp);

DESCRIPTION

     The makecontext() function modifies the user thread context pointed to by ucp, which must have previously been initialized by a call to
     getcontext(3) and had a stack allocated for it.  The context is modified so that it will continue execution by invoking func() with the argu-
     ments (of type int) provided.  The argc argument must be equal to the number of additional arguments provided to makecontext() and also equal
     to the number of arguments to func(), or else the behavior is undefined.

     The ucp->uc_link argument must be initialized before calling makecontext() and determines the action to take when func() returns: if equal to
     NULL, the process exits; otherwise, setcontext(ucp->uc_link) is implicitly invoked.

     The swapcontext() function saves the current thread context in *oucp and makes *ucp the currently active context.

RETURN VALUES

     If successful, swapcontext() returns zero; otherwise -1 is returned and the global variable errno is set appropriately.

ERRORS

     The swapcontext() function will fail if:

     [ENOMEM]		There is not enough stack space in ucp to complete the operation.

SEE ALSO

     setcontext(3), ucontext(3)

BSD
								September 10, 2002							       BSD

MAKECONTEXT(3)						     Linux Programmer's Manual						    MAKECONTEXT(3)

NAME

       makecontext, swapcontext - manipulate user context

SYNOPSIS

       #include <ucontext.h>

       void makecontext(ucontext_t *ucp, void *func(), int argc, ...);
       int swapcontext (ucontext_t *oucp, ucontext_t *ucp);

DESCRIPTION

       In a SysV-like environment, one has the type ucontext_t defined in <ucontext.h> and the four functions getcontext(), setcontext(), makecon-
       text() and swapcontext() that allow user-level context switching between multiple threads of control within a process.

       For the type and the first two functions, see getcontext(2).

       The makecontext() function modifies the context pointed to by ucp (which was obtained from a call to getcontext()).  Before  calling  make-
       context(),  one	should	allocate  a  new  stack for this context, assigning to ucp->uc_stack, and define a successor context, assigning to
       ucp->uc_link.  When this context is later activated (using setcontext() or swapcontext()) then first the function func is called, with  the
       arguments  specified  following argc (where argc must contain the number of these arguments), and when this function returns, the successor
       context is activated. When the successor context pointer is NULL, the thread exits.

       The swapcontext() function saves the current context in the structure pointed to by oucp, and then activates the context pointed to by ucp.

RETURN VALUE

       When successful, makecontext() returns 0 and swapcontext() does not return. (But we may return later, in case oucp is activated,  in  which
       case it looks like swapcontext() returns 0.)  On error, both return -1 and set errno appropriately.

ERRORS

       ENOMEM Insufficient stack space left.

NOTES

       The interpretation of ucp->uc_stack is just as in sigaltstack(2), namely, this struct contains start and length of a memory area to be used
       as stack, regardless of the direction of growth of the stack. So, it is not necessary for the user program to worry about this direction.

CONFORMING TO

       SUSv2, POSIX 1003.1-2001.

SEE ALSO

       getcontext(2), sigaction(2), sigaltstack(2), sigprocmask(2), sigsetjmp(3)

Linux 2.4							    2001-11-15							    MAKECONTEXT(3)