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 replacement  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. Typically, 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 unwound  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 information).

       *      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 libunwind-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(3), 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/.