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libunwind-eh_elf/doc/unw_resume.tex
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\documentclass{article}
\usepackage[fancyhdr,pdf]{latex2man}
\input{common.tex}
\begin{document}
\begin{Name}{3}{unw\_resume}{David Mosberger-Tang}{Programming Library}{unw\_resume}
unw\_resume -- resume execution in a particular stack frame
\end{Name}
\section{Synopsis}
\File{\#include $<$libunwind.h$>$}\\
\Type{int} \Func{unw\_resume}(\Type{unw\_cursor\_t~*}\Var{cursor});\\
\section{Description}
The \Func{unw\_resume}() routine resumes execution at the stack frame
identified by \Var{cursor}. Normally, this is accomplished by
restoring the ``preserved'' (callee-saved) machine state. However, if
execution in any of the stack frames younger (more deeply nested) than
the one identified by \Var{cursor} was interrupted by a signal, then
\Func{unw\_resume}() will restore the entire machine state, including
the ``preserved'' and ``scratch'' (caller-saved) registers, as well as
the signal mask.
Most platforms reserve some registers to pass arguments to exception
handlers (e.g., IA-64 uses \texttt{r15}-\texttt{r18} for this
purpose). These registers are normally treated like ``scratch''
registers. However, if \Prog{libunwind} is used to define an
exception argument register, e.g., by calling \Func{unw\_set\_reg}(),
then \Func{unw\_resume}() will always install the new value as the
contents of that register. In other words, the exception handling
arguments are installed even in cases where normally only the
``preserved'' registers are restored.
Note that \Func{unw\_resume}() does \emph{not} invoke any unwind
handlers (aka, ``personality routines''). If a program needs this, it
will have to do so on its own by obtaining the \Type{unw\_proc\_info\_t}
of each unwound frame and appropriately processing its unwind handler
and language-specific data area (lsda). These steps are generally
dependent on the target-platform and are regulated by the
processor-specific ABI (application-binary interface).
\section{Return Value}
For local unwinding, \Func{unw\_resume}() does not return on success.
For remote unwinding, it returns 0 on success. On failure, the
negative value of one of the errors below is returned.
\section{Errors}
\begin{Description}
\item[\Const{UNW\_EUNSPEC}] An unspecified error occurred.
\item[\Const{UNW\_EBADREG}] A register needed by \Func{unw\_resume}() wasn't
accessible.
\item[\Const{UNW\_EINVALIDIP}] The instruction pointer identified by
\Var{cursor} is not valid.
\item[\Const{UNW\_BADFRAME}] The stack frame identified by
\Var{cursor} is not valid.
\end{Description}
\section{See Also}
\SeeAlso{libunwind(3)},
\SeeAlso{unw\_set\_reg(3)},
sigprocmask(2)
\section{Author}
\noindent
David Mosberger-Tang\\
Hewlett-Packard Labs\\
Palo-Alto, CA 94304\\
Email: \Email{davidm@hpl.hp.com}\\
WWW: \URL{http://www.hpl.hp.com/research/linux/libunwind/}.
\LatexManEnd
\end{document}