GETCONTEXT(P) POSIX Programmer's Manual GETCONTEXT(P)
getcontext, setcontext - get and set current user context
int getcontext(ucontext_t *ucp);
int setcontext(const ucontext_t *ucp);
The getcontext() function shall initialize the structure pointed to by ucp to the current
user context of the calling thread. The ucontext_t type that ucp points to defines the
user context and includes the contents of the calling thread's machine registers, the sig-
nal mask, and the current execution stack.
The setcontext() function shall restore the user context pointed to by ucp. A successful
call to setcontext() shall not return; program execution 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 makecontext(), or by being passed as an argument to a signal
handler. If the ucp argument was created with getcontext(), program execution continues as
if the corresponding call of getcontext() had just returned. If the ucp argument was cre-
ated with makecontext(), program execution continues with the function passed to makecon-
text(). When that function returns, the thread shall continue as if after a call to set-
context() with the ucp argument that was input to makecontext(). 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 thread shall exit when this context returns. The effects of
passing a ucp argument obtained from any other source are unspecified.
Upon successful completion, setcontext() shall not return and getcontext() shall return 0;
otherwise, a value of -1 shall be returned.
No errors are defined.
The following sections are informative.
Refer to makecontext() .
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(), then it is unspecified
whether the context at the time of the corresponding setjmp() call is restored and thus
whether future calls to getcontext() provide an accurate representation of the current
context, since the context restored by longjmp() does not necessarily contain all the
information that setcontext() requires. Signal handlers should use siglongjmp() or setcon-
Conforming applications should not modify or access the uc_mcontext member of ucontext_t.
A conforming 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.
Use of contexts to create alternate stacks is not defined by this volume of
IEEE Std 1003.1-2001.
bsd_signal() , makecontext() , setcontext() , setjmp() , sigaction() , sigaltstack() ,
siglongjmp() , sigprocmask() , sigsetjmp() , the Base Definitions volume of
IEEE Std 1003.1-2001, <ucontext.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 GETCONTEXT(P)