compileAttributes() w/ std::vector<> default value function argument

[RyanHope]

compileAttributes() seems to break when called on a function that includes C++11 style initializer lists as defaults. Here is an example:

cppFunction("std::vector<int> test(std::vector<int> out = {0}) {
  return out;
}")

Error in cppFunction("std::vector test(std::vector out = {0}) {\n return out;\n}") :
No function definition found
In addition: Warning messages:
1: No function found for Rcpp::export attribute at fileee5f1d363260.cpp:5
2: In sourceCpp(code = code, env = env, rebuild = rebuild, showOutput = showOutput, :
No Rcpp::export attributes or RCPP_MODULE declarations found in source

[eddelbuettel]

I briefly tried to construct a standalone C++ program with a one-line main and one such function. It builds, but dies at run-time. Do you have a working self-contained example?

[romainfrancois]

#include <Rcpp.h>
using namespace  Rcpp ;

// [[Rcpp::plugins(cpp11)]]

// [[Rcpp::export]]
std::vector<int> test(std::vector<int> out = {0} ) {
  return out;
}

/*** R
    test()
*/

gives me:

$ RcppScript -v /tmp/test.cpp

Generated extern "C" functions
--------------------------------------------------------


#include <Rcpp.h>

Generated R functions
-------------------------------------------------------

`.sourceCpp_26443_DLLInfo` <- dyn.load('/var/folders/k8/gmp11jks4hl_nwcnk82fbr8m0000gn/T//RtmpyDasm9/sourcecpp_48774fdf7bf/sourceCpp_48020.so')


rm(`.sourceCpp_26443_DLLInfo`)

Building shared library
--------------------------------------------------------

DIR: /var/folders/k8/gmp11jks4hl_nwcnk82fbr8m0000gn/T//RtmpyDasm9/sourcecpp_48774fdf7bf

/Library/Frameworks/R.framework/Resources/bin/R CMD SHLIB -o 'sourceCpp_48020.so' 'test.cpp'
clang++ -std=c++11 -I/Library/Frameworks/R.framework/Resources/include -DNDEBUG  -I/usr/local/include -I/usr/local/include/freetype2 -I/opt/X11/include  -I"/Library/Frameworks/R.framework/Versions/3.1/Resources/library/Rcpp/include"    -fPIC  -std=c++11 -O3 -g -c test.cpp -o test.o
clang++ -std=c++11 -dynamiclib -Wl,-headerpad_max_install_names -undefined dynamic_lookup -single_module -multiply_defined suppress -L/usr/local/lib -o sourceCpp_48020.so test.o -F/Library/Frameworks/R.framework/.. -framework R -Wl,-framework -Wl,CoreFoundation

> test()
Error in eval(expr, envir, enclos) : could not find function "test"
Calls: sourceCpp -> source -> withVisible -> eval -> eval
In addition: Warning messages:
1: No function found for Rcpp::export attribute at test.cpp:6
2: In sourceCpp(tail(args, 1), verbose = "-v" %in% args) :
  No Rcpp::export attributes or RCPP_MODULE declarations found in source
Execution halted

Works fine without the default, so this is something to do with the default arg.

[RyanHope]

Yes it works fine with out the default... the whole point of this post is to figure out how to set a default for this function (in the C++ code, not the R code).

[eddelbuettel]

Well as I mentioned it doesn't even work without Rcpp:

edd@max:/tmp$ cat ryan.cpp 

#include <vector>

std::vector<int> test(std::vector<int> out = {0} ) {
  return out;
}

int main(void) {
  std::vector<int> v = test();
}
edd@max:/tmp$ g++ -std=c++11 ryan.cpp -o ryan
edd@max:/tmp$ ./ryan 
*** Error in `./ryan': double free or corruption (fasttop): 0x0000000001349010 ***
Aborted (core dumped)
edd@max:/tmp

[jjallaire]

I would back away from trying to use C++11 uniform initialization syntax.
Note that the C++ parser inside Rcpp is nowhere near complete but generally
works in 99% of real-world use cases. This case isn't handled yet and it
might be a lot of work for us to make it so.

On Thu, Oct 9, 2014 at 8:00 AM, Dirk Eddelbuettel notifications@github.com
wrote:

Well as I mentioned it doesn't even work without Rcpp:

edd@max:/tmp$ cat ryan.cpp
#include

std::vector test(std::vector out = {0} ) {
return out;}

int main(void) {
std::vector v = test();}
edd@max:/tmp$ g++ -std=c++11 ryan.cpp -o ryan
edd@max:/tmp$ ./ryan
*** Error in `./ryan': double free or corruption (fasttop): 0x0000000001349010 ***
Aborted (core dumped)
edd@max:/tmp

—
Reply to this email directly or view it on GitHub
#190 (comment).

[eddelbuettel]

Agreed. Shall we add a short paragraph to the Rcpp Attributes vignette?

[RyanHope]

I actually don't care if the solution is C++11, that just seemed like the path of least resistance when I was trying things out. I just need a way to set a default vector.

[RyanHope]

Also, this works...

#include <vector>

std::vector<int> test(std::vector<int> out = std::vector<int>({0})) {
  return out;
}

int main(void) {
  std::vector<int> v = test();
}

But not within Rcpp...

> cppFunction("std::vector<int> test(std::vector<int> out = std::vector<int>({0})) {
+   return out;
+ }")
Error in cppFunction("std::vector<int> test(std::vector<int> out = std::vector<int>({0})) {\n  return out;\n}") : 
  No function definition found
In addition: Warning message:
In sourceCpp(code = code, env = env, rebuild = rebuild, showOutput = showOutput,  :
  No Rcpp::export attributes or RCPP_MODULE declarations found in source

[jjallaire]

This would also work:

// [[Rcpp::export]]
IntegerVector makeVector(IntegerVector vec = IntegerVector::create(0)) {
return vec;
}

On Thu, Oct 9, 2014 at 8:31 AM, Ryan Hope notifications@github.com wrote:

Also, this works...

#include
std::vector test(std::vector out = std::vector({0})) {
return out;}
int main(void) {
std::vector v = test();}

—
Reply to this email directly or view it on GitHub
#190 (comment).

[jjallaire]

Yes, we could definitely flesh out that section (and in fact the whole
vignette!). Let me try to do that for the next release.

On Thu, Oct 9, 2014 at 8:13 AM, Dirk Eddelbuettel notifications@github.com
wrote:

Agreed. Shall we add a short paragraph to the Rcpp Attributes vignette?

—
Reply to this email directly or view it on GitHub
#190 (comment).

[romainfrancois]

As default arguments are handled by converting to default argument to the R function, you could sort of do it after the fact, i.e. with:

#include <Rcpp.h>
using namespace  Rcpp ;

// [[Rcpp::plugins(cpp11)]]

// [[Rcpp::export]]
std::vector<int> test(std::vector<int> out ) {
  return out;
}

/*** 
formals(test) <- alist(out=0L)
test()
*/

[RyanHope]

Using Rcpp type vector instead of std::vector is an acceptable work around / solution so I am going to close this but it would be nice if the defaults could be std::vector to avoid unnecessary conversions to and from Rcpp types.