Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

makecontext(3) [osx man page]

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

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

Check Out this Related Man Page

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

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)
Man Page