[Rcpp-devel] Interrupts in compiled code.

How about just using R_CheckUserInterrupt()?

Davor


On 2010-12-08, at 1:02 PM, Dirk Eddelbuettel wrote:

On 8 December 2010 at 13:41, Andrew Redd wrote:
| I have an MCMC chain that runs entirely in c++ with Rcpp.  It sometimes

runs

| for a vary long time and I want to interrupt it.  Is there an efficient

easy

| way to include catching an interupt signal and either aborting or

returning

| results to that point?  This might be understood well, if so I

apologize.

Great question.

Here is a simple example that uses a standard C interrupt handler to set

a

standard C++ exception to abort:

----------------------------------------------------------------

#include <csignal>
#include <Rcpp.h>

void intHandler(int dummy=0) {
 std::cerr << "In intHandler" << std::endl;
 throw std::runtime_error("Interception caught");
}

RcppExport SEXP foo(void) {

 try {

   signal(SIGINT, intHandler);
   signal(SIGKILL, intHandler);

   while (true) {
     sleep(1);                        // not doing much
   }
   return R_NilValue;

 } catch(std::exception &ex) {
   std::cerr << "In catch of std::exeception" << std::endl;
   // here you insert some clenup
   forward_exception_to_r(ex);

 } catch(...) {
   ::Rf_error("c++ exception (unknown reason)");
 }

 return R_NilValue;
}

----------------------------------------------------------------

which I then quickly turned into a shared object, load and ran at the
command-line [1]

edd at max:/tmp/andrew$ PKG_CPPFLAGS=`r -e'Rcpp:::CxxFlags()'` PKG_LIBS=`r

-e'Rcpp:::LdFlags()'` R CMD SHLIB int2throw.cpp

ccache g++ -I/usr/share/R/include

-I/usr/local/lib/R/site-library/Rcpp/include     -fpic  -g -O3 -Wall -pipe
-pedantic -Wno-variadic-macros -c int2throw.cpp -o int2throw.o

g++ -shared -o int2throw.so int2throw.o

-L/usr/local/lib/R/site-library/Rcpp/lib -lRcpp
-Wl,-rpath,/usr/local/lib/R/site-library/Rcpp/lib -L/usr/lib64/R/lib -lR

edd at max:/tmp/andrew$ r -e'dyn.load("int2throw.so"); .Call("foo")'
^CIn intHandler
In catch of std::exeception
Error in cpp_exception(message = "Interception caught", class =

"std::runtime_error") :

 Interception caught
Execution halted
edd at max:/tmp/andrew$
edd at max:/tmp/andrew$


After lauching it from the one-line littler (r) expression, I pressed

Ctrl-C

which then got us into the interrupt which threw the exception which lead

to

the end.

In Rscript it looks a little more orderly on the unwind:

edd at max:/tmp/andrew$ Rscript -e 'dyn.load("int2throw.so"); .Call("foo")'
 C-c C-cIn intHandler
In catch of std::exeception
Error in cpp_exception(message = "Interception caught", class =

"std::runtime_error") :

 Interception caught
Calls: .Call -> cpp_exception
Execution halted
edd at max:/tmp/andrew$


Hope this helps,  Dirk


[1] Not sure why I didn't use inline today...


--
Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com