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'\" t
.\" Manual page created with latex2man on Thu Aug 16 09:44:45 MDT 2007
.\" NOTE: This file is generated, DO NOT EDIT.
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.TH "UNW\\_RESUME" "3" "16 August 2007" "Programming Library " "Programming Library "
.SH NAME
unw_resume
\-\- resume execution in a particular stack frame
.PP
.SH SYNOPSIS
.PP
#include <libunwind.h>
.br
.PP
int
unw_resume(unw_cursor_t *cp);
.br
.PP
.SH DESCRIPTION
.PP
The unw_resume()
routine resumes execution at the stack frame
identified by cp\&.
The behavior of this routine differs
slightly for local and remote unwinding.
.PP
For local unwinding, unw_resume()
restores the machine state
and then directly resumes execution in the target stack frame. Thus
unw_resume()
does not return in this case. Restoring the
machine state normally involves restoring the ``preserved\&''
(callee\-saved) registers. However, if execution in any of the stack
frames younger (more deeply nested) than the one identified by
cp
was interrupted by a signal, then unw_resume()
will
restore all registers as well as the signal mask. Attempting to call
unw_resume()
on a cursor which identifies the stack frame of
another thread results in undefined behavior (e.g., the program may
crash).
.PP
For remote unwinding, unw_resume()
installs the machine state
identified by the cursor by calling the access_reg
and
access_fpreg
accessor callbacks as needed. Once that is
accomplished, the resume
accessor callback is invoked. The
unw_resume
routine then returns normally (that is, unlikely
for local unwinding, unw_resume
will always return for remote
unwinding).
.PP
Most platforms reserve some registers to pass arguments to exception
handlers (e.g., IA\-64 uses r15\-r18
for this
purpose). These registers are normally treated like ``scratch\&''
registers. However, if libunwind
is used to set an exception
argument register to a particular value (e.g., via
unw_set_reg()),
then unw_resume()
will install this
value as the contents of the register. In other words, the exception
handling arguments are installed even in cases where normally only the
``preserved\&'' registers are restored.
.PP
Note that unw_resume()
does \fInot\fP
invoke any unwind
handlers (aka, ``personality routines\&''). If a program needs this, it
will have to do so on its own by obtaining the 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).
.PP
.SH RETURN VALUE
.PP
For local unwinding, 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.
.PP
.SH THREAD AND SIGNAL SAFETY
.PP
unw_resume()
is thread\-safe. If cursor cp
is in the
local address\-space, this routine is also safe to use from a signal
handler.
.PP
.SH ERRORS
.PP
.TP
UNW_EUNSPEC
An unspecified error occurred.
.TP
UNW_EBADREG
A register needed by unw_resume()
wasn\&'t
accessible.
.TP
UNW_EINVALIDIP
The instruction pointer identified by
cp
is not valid.
.TP
UNW_BADFRAME
The stack frame identified by
cp
is not valid.
.PP
.SH SEE ALSO
.PP
libunwind(3),
unw_set_reg(3),
sigprocmask(2)
.PP
.SH AUTHOR
.PP
David Mosberger\-Tang
.br
Email: \fBdmosberger@gmail.com\fP
.br
WWW: \fBhttp://www.nongnu.org/libunwind/\fP\&.
.\" NOTE: This file is generated, DO NOT EDIT.
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