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89 lines
3.3 KiB
TeX
89 lines
3.3 KiB
TeX
\documentclass{article}
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\usepackage[fancyhdr,pdf]{latex2man}
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\input{common.tex}
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\begin{document}
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\begin{Name}{3}{libunwind-setjmp}{David Mosberger-Tang}{Programming Library}{libunwind-based non-local gotos}libunwind-setjmp -- libunwind-based non-local gotos
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\end{Name}
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\section{Synopsis}
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\File{\#include $<$setjmp.h$>$}\\
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\noindent
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\Type{int} \Func{setjmp}(\Type{jmp\_buf}~\Var{env});\\
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\Type{void} \Func{longjmp}(\Type{jmp\_buf}~\Var{env}, \Type{int}~\Var{val});\\
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\Type{int} \Func{\_setjmp}(\Type{jmp\_buf}~\Var{env});\\
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\Type{void} \Func{\_longjmp}(\Type{jmp\_buf}~\Var{env}, \Type{int}~\Var{val});\\
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\Type{int} \Func{setjmp}(\Type{sigjmp\_buf}~\Var{env}, \Type{int}~\Var{savemask});\\
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\Type{void} \Func{siglongjmp}(\Type{sigjmp\_buf}~\Var{env}, \Type{int}~\Var{val});\\
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\section{Description}
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The \Prog{unwind-setjmp} library offers a \Prog{libunwind}-based
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implementation of non-local gotos. This implementation is intended to
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be a drop-in replacement for the normal, system-provided routines of
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the same name. The main advantage of using the \Prog{unwind-setjmp}
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library is that setting up a non-local goto via one of the
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\Func{setjmp}() routines is very fast. Typically, just 2 or 3 words
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need to be saved in the jump-buffer (plus one call to
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\Func{sigprocmask}(2), in the case of \Func{sigsetjmp}). On the
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other hand, executing a non-local goto by calling one of the
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\Func{longjmp}() routines tends to be much slower than with the
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system-provided routines. In fact, the time spent on a
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\Func{longjmp}() will be proportional to the number of call frames
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that exist between the points where \Func{setjmp}() and
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\Func{longjmp}() were called. For this reason, the
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\Prog{unwind-setjmp} library is beneficial primarily in applications
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that frequently call \Func{setjmp}() but only rarely call
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\Func{longjmp}().
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\section{Caveats}
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\begin{itemize}
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\item The correct operation of this library depends on the presence of
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correct unwind information. On newer platforms, this is rarely an
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issue. On older platforms, care needs to be taken to
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ensure that each of the functions whose stack frames may have to be
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unwound during a \Func{longjmp}() have correct unwind information
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(on those platforms, there is usually a compiler-switch, such as
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\Opt{-funwind-tables}, to request the generation of unwind
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information).
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\item The contents of \Type{jmp\_buf} and \Type{sigjmp\_buf} as setup
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and used by these routines is completely different from the ones
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used by the system-provided routines. Thus, a jump-buffer created
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by the libunwind-based \Func{setjmp}()/\Func{\_setjmp} may only be
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used in a call to the libunwind-based
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\Func{longjmp}()/\Func{\_longjmp}(). The analogous applies for
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\Type{sigjmp\_buf} with \Func{sigsetjmp}() and \Func{siglongjmp}().
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\end{itemize}
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\section{Files}
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\begin{Description}
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\item[\Opt{-l}\File{unwind-setjmp}] The library an application should
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be linked against to ensure it uses the libunwind-based non-local
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goto routines.
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\end{Description}
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\section{See Also}
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\SeeAlso{libunwind(3)},
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setjmp(3), longjmp(3),
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\_setjmp(3), \_longjmp(3),
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sigsetjmp(3), siglongjmp(3)
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\section{Author}
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\noindent
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David Mosberger-Tang\\
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Hewlett-Packard Labs\\
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Palo-Alto, CA 94304\\
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Email: \Email{davidm@hpl.hp.com}\\
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WWW: \URL{http://www.hpl.hp.com/research/linux/libunwind/}.
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\LatexManEnd
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\end{document}
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