osf1 man page for swapcontext

makecontext(2)							System Calls Manual						    makecontext(2)

NAME
       makecontext, swapcontext - Manipulate user level context switching

SYNOPSIS
       #include  <ucontext.h>

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

STANDARDS
       Interfaces documented on this reference page conform to industry standards as follows:

       makecontext(), swapcontext():  XSH5.0

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

PARAMETERS
       Provides a pointer to a ucontext structure, defined in the <ucontext.h> header file.  The ucontext structure contains the signal mask, exe-
       cution stack, and machine registers. (See ucontext(5) for more information about the format of the ucontext structure.)	Specifies a  func-
       tion  to be called when program execution begins in the new context.  Specifies the number of parameters passed to the func() function. You
       include the parameters themselves following the argc parameter.	Pointer to the ucontext structure that holds the  current  context  struc-
       ture.

DESCRIPTION
       The  makecontext() function modifies the context specified by the ucp parameter.  Before you call the makecontext() function, call the get-
       context() function to initialize the ucp parameter.

       Before you call the makecontext() function, you should allocate a stack for the new context. Also, you should initialize the uc_link member
       of the ucontext structure.  This member determines the context that is resumed when the context modified by makecontext() returns. You ini-
       tialize the uc_link member by calling the getcontext() function.

       To execute the new context, call the setcontext() or swapcontext() function. Program execution begins by calling the function specified	in
       the func parameter.  Any parameters you specify following the argc parameter are passed to the func() function.

       The  swapcontext()  function  switches  between	two  user contexts. The function stores the current context in the oucp parameter. It then
       switches execution to the context described by the ucp parameter.  When the new context finishes execution, control returns to the  context
       described by the oucp parameter.

RETURN VALUES
       The makecontext() function does not return.

       On  success,  the  swapcontext()  function  returns 0 (zero). On failure the swapcontext() function returns a value of -1 and sets errno to
       indicate the error.

ERRORS
       The makecontext() or swapcontext() functions set errno to the specified values for the following conditions: The ucp parameter has too lit-
       tle stack left to complete the operation.

SEE ALSO
       Functions:  exit(2), getcontext(2), sigaction(2), sigprocmask(2)

       Files:  ucontext(5)

       Standards:  standards(5)

																    makecontext(2)