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 \documentclass{article} \usepackage[fancyhdr,pdf]{latex2man} \input{common.tex} \begin{document} \begin{Name}{3}{libunwind-setjmp}{David Mosberger-Tang}{Programming Library}{libunwind-based non-local gotos}libunwind-setjmp -- libunwind-based non-local gotos \end{Name} \section{Synopsis} \File{\#include $<$setjmp.h$>$}\\ \noindent \Type{int} \Func{setjmp}(\Type{jmp\_buf}~\Var{env});\\ \Type{void} \Func{longjmp}(\Type{jmp\_buf}~\Var{env}, \Type{int}~\Var{val});\\ \Type{int} \Func{\_setjmp}(\Type{jmp\_buf}~\Var{env});\\ \Type{void} \Func{\_longjmp}(\Type{jmp\_buf}~\Var{env}, \Type{int}~\Var{val});\\ \Type{int} \Func{sigsetjmp}(\Type{sigjmp\_buf}~\Var{env}, \Type{int}~\Var{savemask});\\ \Type{void} \Func{siglongjmp}(\Type{sigjmp\_buf}~\Var{env}, \Type{int}~\Var{val});\\ \section{Description} The \Prog{unwind-setjmp} library offers a \Prog{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 \Prog{unwind-setjmp} library is that setting up a non-local goto via one of the \Func{setjmp}() routines is very fast. Typically, just 2 or 3 words need to be saved in the jump-buffer (plus one call to \Func{sigprocmask}(2), in the case of \Func{sigsetjmp}). On the other hand, executing a non-local goto by calling one of the \Func{longjmp}() routines tends to be much slower than with the system-provided routines. In fact, the time spent on a \Func{longjmp}() will be proportional to the number of call frames that exist between the points where \Func{setjmp}() and \Func{longjmp}() were called. For this reason, the \Prog{unwind-setjmp} library is beneficial primarily in applications that frequently call \Func{setjmp}() but only rarely call \Func{longjmp}(). \section{Caveats} \begin{itemize} \item 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 \Func{longjmp}() have correct unwind information (on those platforms, there is usually a compiler-switch, such as \Opt{-funwind-tables}, to request the generation of unwind information). \item The contents of \Type{jmp\_buf} and \Type{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 \Func{setjmp}()/\Func{\_setjmp} may only be used in a call to the libunwind-based \Func{longjmp}()/\Func{\_longjmp}(). The analogous applies for \Type{sigjmp\_buf} with \Func{sigsetjmp}() and \Func{siglongjmp}(). \end{itemize} \section{Files} \begin{Description} \item[\Opt{-l}\File{unwind-setjmp}] The library an application should be linked against to ensure it uses the libunwind-based non-local goto routines. \end{Description} \section{See Also} \SeeAlso{libunwind(3)}, setjmp(3), longjmp(3), \_setjmp(3), \_longjmp(3), sigsetjmp(3), siglongjmp(3) \section{Author} \noindent David Mosberger-Tang\\ Email: \Email{dmosberger@gmail.com}\\ WWW: \URL{http://www.nongnu.org/libunwind/}. \LatexManEnd \end{document}