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LIBUNWIND-SETJMP(3libunwind) Programming Library  LIBUNWIND-SETJMP(3libunwind)

NAME
       libunwind-setjmp	-- libunwind-based non-local gotos

SYNOPSIS
       #include	<setjmp.h>

       int setjmp(jmp_buf env);
       void longjmp(jmp_buf env, int val);
       int _setjmp(jmp_buf env);
       void _longjmp(jmp_buf env, int val);
       int sigsetjmp(sigjmp_buf	env, int savemask);
       void siglongjmp(sigjmp_buf env, int val);

DESCRIPTION
       The  unwind-setjmp  library  offers a libunwind-based implementation of
       non-local gotos.	This implementation is intended	to be  a  drop-in  re-
       placement  for  the  normal, system-provided routines of	the same name.
       The main	advantage of using the unwind-setjmp library is	 that  setting
       up a non-local goto via one of the setjmp() routines is very fast. Typ-
       ically, just 2 or 3 words need to be saved in the jump-buffer (plus one
       call  to	sigprocmask(2),	in the case of sigsetjmp).  On the other hand,
       executing a non-local goto by calling one  of  the  longjmp()  routines
       tends  to  be  much  slower  than with the system-provided routines. In
       fact, the time spent on a longjmp() will	be proportional	to the	number
       of  call	 frames	 that  exist  between  the  points  where setjmp() and
       longjmp() were called. For this reason, the  unwind-setjmp  library  is
       beneficial  primarily in	applications that frequently call setjmp() but
       only rarely call	longjmp().

CAVEATS
       *      The correct operation of this library depends on the presence of
	      correct unwind information. On newer platforms, this  is	rarely
	      an  issue.  On older platforms, care needs to be taken to	ensure
	      that each	of the functions whose stack frames may	have to	be un-
	      wound during a longjmp() have  correct  unwind  information  (on
	      those  platforms,	 there	is  usually a compiler-switch, such as
	      -funwind-tables, to request the generation  of  unwind  informa-
	      tion).

       *      The  contents  of	 jmp_buf  and  sigjmp_buf as setup and used by
	      these routines is	completely different from the ones used	by the
	      system-provided routines.	Thus, a	jump-buffer created by the li-
	      bunwind-based setjmp()/_setjmp may only be used in a call	to the
	      libunwind-based longjmp()/_longjmp().  The analogous applies for
	      sigjmp_buf with sigsetjmp() and siglongjmp().

FILES
       -lunwind-setjmp
	       The library an application should be linked against  to	ensure
	      it uses the libunwind-based non-local goto routines.

SEE ALSO
       libunwind(3libunwind),  setjmp(3), longjmp(3), _setjmp(3), _longjmp(3),
       sigsetjmp(3), siglongjmp(3)

AUTHOR
       David Mosberger-Tang
       Email: dmosberger@gmail.com
       WWW: http://www.nongnu.org/libunwind/.

Programming Library		29 August 2023	  LIBUNWIND-SETJMP(3libunwind)

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