interrupting native code

On May 20, 2008, at 10:58 AM, Kjell Konis wrote:

I would actually prefer a mechanism that simply returns a flag  
indicating that an interrupt has been requested. Then I would be  
able to clean up and return on my own - no longjmp required. Also,  
it would be useful if there was a function similar to  
R_ProcessEvents that only dealt with keeping the GUI responsive.

I don't understand what you mean by the last sentence - that is  
exactly what R_ProcessEvents is for - or am I missing something?

Cheers,

Simon

Cheers,
Kjell


On 16 mai 08, at 13:54, Luke Tierney wrote:

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

-- 
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

-- 
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

-- 
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