Are there any known issues regarding memory corruption caused by lists created
inside of Rcpp? I started noticing some inconsistencies in the data returned by
my app, and was able to reduce the issue to the following reproducible example.
It seems to suggest that lists created in Rcpp and returned to R can cause
sporadic memory corruption. See code below for a demonstration:
require(inline)require(Rcpp)
testFun <- local( {
fun <- cxxfunction( signature(), ' return
Rcpp::List::create(Rcpp::Named( "testVar" ) = wrap(10)); ', plugin =
"Rcpp" )
function(){ fun() }} )
# generate the result set -- you would expect a numeric vector that consists of
repetition of the value 10testOutcome = mapply( function(i) { fTouch
= testFun() return(fTouch$testVar) }, 1:5612062)
# The result ends up being something other than what you'd
expecttypeof(testOutcome) for (i in 1:length(testOutcome)) { if
(testOutcome[[i]] != 10) { cat(i, "\n") }}
You'll notice two things here. First, mapply fails to coerce the returned
results to a vector (since in some cases the return from testFun seems to have
more than 1 element) and second, not all return values are equal to 10, as you
would expect. The actual position in the vector of the corrupted data is
sporadic. If you keep running this over and over again, you'll see the wrong
value in different places. Sometimes you can even get R to crash after multiple
runs. On rare occasions there will be no errors at all. For some reason you
tend to see the most errors on the first run, especially if you open a new
instance of R.
If you replace the line "fTouch = testFun()" with a native call to R "fTouch =
list(testVar = 10)" then everything works fine. Also returning a NumericVector
instead of a list also works fine -- the issue seems to appear after
encapsulating the return value in a list inside of Rcpp.
I am using R 2.14.2 on Win32 & Win64. Rcpp version 0.9.10.
Thanks,Ilya
_______________________________________________
Rcpp-devel mailing list
Rcpp-devel@lists.r-forge.r-project.org
https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
