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setcontext(2) [netbsd man page]

GETCONTEXT(2)						      BSD 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 Release 4 UNIX. BSD
April 28, 2010 BSD

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getcontext(2)							   System Calls 						     getcontext(2)

NAME
getcontext, setcontext - get and set current user context SYNOPSIS
#include <ucontext.h> int getcontext(ucontext_t *ucp); int setcontext(const ucontext_t *ucp); DESCRIPTION
The getcontext() function initializes the structure pointed to by ucp to the current user context of the calling process. The ucontext_t type that ucp points to defines the user context and includes the contents of the calling process' machine registers, the signal mask, and the current execution stack. The setcontext() function restores the user context pointed to by ucp. A successful call to setcontext() does not return; program execu- tion 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 by being passed as an argument to a signal handler. If the ucp argument was created with getcontext(), program execu- tion continues as if the corresponding call of getcontext() had just returned. If the ucp argument was created with makecontext(3C), pro- gram execution continues with the function passed to makecontext(3C). When that function returns, the process continues as if after a call to setcontext() with the ucp argument that was input to makecontext(3C). If the ucp argument was passed to a signal handler, program execu- tion continues with the program instruction following the instruction interrupted by the signal. 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 process will exit when this context returns. The effects of passing a ucp argument obtained from any other source are unspecified. RETURN VALUES
On successful completion, setcontext() does not return and getcontext() returns 0. Otherwise, -1 is returned. ERRORS
No errors are defined. USAGE
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(3UCB), then it is unspecified whether the context at the time of the corresponding setjmp(3UCB) call is restored and thus whether future calls to getcontext() will provide an accurate representation of the current context, since the context restored by longjmp(3UCB) may not contain all the information that setcontext() requires. Signal handlers should use siglongjmp(3C) instead. Portable applications should not modify or access the uc_mcontext member of ucontext_t. A portable 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. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ SEE ALSO
sigaction(2), sigaltstack(2), sigprocmask(2), bsd_signal(3C), makecontext(3C), setjmp(3UCB), sigsetjmp(3C), ucontext.h(3HEAD), attributes(5), standards(5) SunOS 5.10 5 Feb 2001 getcontext(2)
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