From luke at stat.uiowa.edu  Fri May 16 13:54:23 2008
From: luke at stat.uiowa.edu (Luke Tierney)
Date: Fri, 16 May 2008 06:54:23 -0500 (CDT)
Subject: [Rd] interrupting native code
In-Reply-To: <A213708A-3BA2-4109-B24E-F862DCED9BBF@epfl.ch>
References: <B2675BBE-97A5-4012-A855-6955F6EE8246@epfl.ch>
	<alpine.LFD.1.10.0805151533180.22788@gannet.stats.ox.ac.uk>
	<80A6B7A3-7979-4A70-8FBF-3EBA753E093E@epfl.ch>
	<alpine.LFD.1.10.0805161142330.27836@gannet.stats.ox.ac.uk>
	<A213708A-3BA2-4109-B24E-F862DCED9BBF@epfl.ch>
Message-ID: <Pine.LNX.4.64.0805160635510.10050@itasca2.wildberry.org>

I'm not sure you can make this work as some of the things needed
either are or should be private to the core implementation and not
available to package code.  In any case I would not recommend this
approach for two reasons.  First, details of what happens in interrupt
checking are subject to change and your code would miss those changes
unless you track them carefully.  More importantly, several things
here could generate an error that results in a longjmp and leaves your
code in an unstable state.

What is needed for this is a mechanism for detecting an interrupt but
not doing the longjmp, just returning a flag that a longjmp is needed
and enough information to allow it to be made after cleanup code has
been run.  This has been on my to do list for a while but getting the
semantics right is tricky and so it hasn't happened yet.  Hopefully it
will be in 2.8.0.  In the interim you can cobble something together
using R_ToplevelExec, interpreting all FALSE return values as user
interrupts.

Another option, also under consideration but not available yet, is a C
mechanism for registering cleanup operations if a longjmp occurs.  A
quick and dirty version of that could be provided fairly easily but a
better version, which would be preferable in the long run, requires a
rewrite of the code that implements jumps and cleanup/on.exit actions.
This may take a bit longer to implement.

Best,

luke

On Fri, 16 May 2008, Kjell Konis wrote:

> You mean something like this (I return 1 instead of calling onintr())? Will 
> HAVE_AQUA and Win32 be appropriately defined when building my package (I 
> can't see how to check with R CMD config)?
>
> int My_CheckUserInterrupt(void)
> {
>   R_CheckStack();
>
> #if  ( defined(HAVE_AQUA) )
>
> /* R_ProcessEvents() from unix/aqua.c*/
>
> if (ptr_R_ProcessEvents)
>   ptr_R_ProcessEvents();
> if (R_interrupts_pending)
>   return(1);
>
> #elseif ( defined(Win32) )
>
> /* R_ProcessEvents() from gnuwin32/system.c */
>
>   while (peekevent()) doevent();
>   if (UserBreak) {
> 	UserBreak = FALSE;
> 	return(1);
>   }
>   R_CallBackHook();
>   if(R_tcldo) R_tcldo();
>
> #else
>
>   R_PolledEvents();
>   if (R_interrupts_pending)
> 	return(1);
>
> #endif
>
> return(0);
> }
>
>
>
>
> On 16 mai 08, at 12:43, Prof Brian Ripley wrote:
>
>> On Fri, 16 May 2008, Kjell Konis wrote:
>> 
>>> The problem is that my package uses an external pointer to keep track of a 
>>> structure created by the lp_solve library. If I use R_CheckUserInterrupt 
>>> in the lp_solve abort function it leaves the structure in a messed-up 
>>> state after an interrupt occurs. I am not even able to free the memory 
>>> allocated in the structure. I need to be able to tell the lp_solve 
>>> functions to interrupt themselves if I am going to support interrupts at 
>>> all.
>>> 
>>> I took a longer look at errors.c and it seems my solution should work as 
>>> long as neither HAVE_AQUA nor Win32 are defined. Under the circumstances, 
>>> I think that's the best I can do.
>>> 
>>> Any suggestions for a UI independent way to check for interrupts would be 
>>> appreciated.
>> 
>> Why not use the same code as R_CheckUserInterrupt but instead of calling 
>> onintr, call your own interrupt routine?
>> 
>>> 
>>> Thanks,
>>> Kjell
>>> 
>>> On 15 mai 08, at 16:41, Prof Brian Ripley wrote:
>>> 
>>>> How is R_interrupts_pending going to be set?
>>>> It is set in the interrupt handler for SIGINT, but that is not the only 
>>>> way to indicate an interrupt, and it is not necessarily available to 
>>>> users of GUIs and embedded R.
>>>> Without servicing the GUIs all interaction will be dead, including 
>>>> sending an interrrupt from menus/buttons/keyboard.  See the comment in 
>>>> the code for R_CheckUserInterrupt.
>>>> On Thu, 15 May 2008, Kjell Konis wrote:
>>>>> Hello,
>>>>> I have some native code that I would like to allow users to interrupt. 
>>>>> However, I would like to do it more gracefully than with 
>>>>> R_CheckUserInterrupt(). The solution I came up with is to call the 
>>>>> following abort function periodically - if it returns 1 then I clean up 
>>>>> and return.
>>>>> int __WINAPI RlpSolveAbortFunction(lprec *lp, void *userhandle)
>>>>> {
>>>>> if(R_interrupts_pending)
>>>>> return(1);
>>>>> return(0);
>>>>> }
>>>>> This seems to work fine on Mac (sans Aqua) and Linux. Is this going to 
>>>>> be portable?  Also, is there anything else I need to do?  For instance 
>>>>> set R_interrupts_pending to 0 after I respond to it?
>>>>> Thanks.
>>>>> Kjell
>>>>> ______________________________________________
>>>>> R-devel at r-project.org mailing list
>>>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>>> -- 
>>>> Brian D. Ripley,                  ripley at stats.ox.ac.uk
>>>> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
>>>> University of Oxford,             Tel:  +44 1865 272861 (self)
>>>> 1 South Parks Road,                     +44 1865 272866 (PA)
>>>> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
>>> 
>>> ______________________________________________
>>> R-devel at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>> 
>> -- 
>> Brian D. Ripley,                  ripley at stats.ox.ac.uk
>> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
>> University of Oxford,             Tel:  +44 1865 272861 (self)
>> 1 South Parks Road,                     +44 1865 272866 (PA)
>> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel

-- 
Luke Tierney
Chair, Statistics and Actuarial Science
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
    Actuarial Science
241 Schaeffer Hall                  email:      luke at stat.uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu



[Rd] interrupting native code
Luke Tierney