(Apologies for sending this twice -- the formatting on the first email got
completely mangled)
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 ensd 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 _______________________________________________
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