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longjmp(3) [linux man page]

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

NAME
longjmp, siglongjmp - nonlocal jump to a saved stack context SYNOPSIS
#include <setjmp.h> void longjmp(jmp_buf env, int val); void siglongjmp(sigjmp_buf env, int val); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): siglongjmp(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_C_SOURCE DESCRIPTION
longjmp() and setjmp(3) are useful for dealing with errors and interrupts encountered in a low-level subroutine of a program. longjmp() restores the environment saved by the last call of setjmp(3) with the corresponding env argument. After longjmp() is completed, program execution continues as if the corresponding call of setjmp(3) had just returned the value val. longjmp() cannot cause 0 to be returned. If longjmp() is invoked with a second argument of 0, 1 will be returned instead. siglongjmp() is similar to longjmp() except for the type of its env argument. If, and only if, the sigsetjmp(3) call that set this env used a nonzero savesigs flag, siglongjmp() also restores the signal mask that was saved by sigsetjmp(3). RETURN VALUE
These functions never return. CONFORMING TO
C89, C99, and POSIX.1-2001 specify longjmp(). POSIX.1-2001 specifies siglongjmp(). NOTES
POSIX does not specify whether longjmp() will restore the signal context (see setjmp(3) for some more details). If you want to portably save and restore signal masks, use sigsetjmp() and siglongjmp(). The values of automatic variables are unspecified after a call to longjmp() if they meet all the following criteria: o they are local to the function that made the corresponding setjmp(3) call; o their values are changed between the calls to setjmp(3) and longjmp(); and o they are not declared as volatile. Analogous remarks apply for siglongjmp(). longjmp() and siglongjmp() make programs hard to understand and maintain. If possible an alternative should be used. SEE ALSO
setjmp(3), sigsetjmp(3) COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. 2009-01-13 LONGJMP(3)

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

NAME
setjmp, sigsetjmp - save stack context for nonlocal goto SYNOPSIS
#include <setjmp.h> int setjmp(jmp_buf env); int sigsetjmp(sigjmp_buf env, int savesigs); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): setjmp(): see NOTES. sigsetjmp(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_C_SOURCE DESCRIPTION
setjmp() and longjmp(3) are useful for dealing with errors and interrupts encountered in a low-level subroutine of a program. setjmp() saves the stack context/environment in env for later use by longjmp(3). The stack context will be invalidated if the function which called setjmp() returns. sigsetjmp() is similar to setjmp(). If, and only if, savesigs is nonzero, the process's current signal mask is saved in env and will be restored if a siglongjmp(3) is later performed with this env. RETURN VALUE
setjmp() and sigsetjmp() return 0 if returning directly, and nonzero when returning from longjmp(3) or siglongjmp(3) using the saved con- text. CONFORMING TO
C89, C99, and POSIX.1-2001 specify setjmp(). POSIX.1-2001 specifies sigsetjmp(). NOTES
POSIX does not specify whether setjmp() will save the signal mask. In System V it will not. In 4.3BSD it will, and there is a function _setjmp that will not. By default, Linux/glibc follows the System V behavior, but the BSD behavior is provided if the _BSD_SOURCE feature test macro is defined and none of _POSIX_SOURCE, _POSIX_C_SOURCE, _XOPEN_SOURCE, _XOPEN_SOURCE_EXTENDED, _GNU_SOURCE, or _SVID_SOURCE is defined. If you want to portably save and restore signal masks, use sigsetjmp() and siglongjmp(). setjmp() and sigsetjmp() make programs hard to understand and maintain. If possible an alternative should be used. SEE ALSO
longjmp(3), siglongjmp(3) COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. 2009-06-26 SETJMP(3)

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