BUG: cannot compile r-cpp11 when using MSVC's STL as C++ stdlib

[h-vetinari]

In conda-forge we're building under some different constraints than for CRAN, which leads us to use different compilers etc.

As it turns out a change in r-cpp11 v0.4.4 ended up breaking the R-bindings for arrow, only that we weren't able to root-cause the issue at the time, and so we haven't had windows builds for r-arrow since about 8 month.

After some digging together with the arrow folks, it seems to be a combination of two things

• the change to std::transform in 28538e5
• the fact that cpp11::writable::r_vector<double>::iterator has no copy assignment operator (implicitly deleted by the compiler)

It seems that the STL stumbles over this combination in its implementation of std::transform:

In file included from altrep.cpp:18:
In file included from .\./arrow_types.h:22:
In file included from .\.\./arrow_cpp11.h:20:
In file included from C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\memory:14:
In file included from C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\xmemory:15:
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\xutility:1408:13: error: object of type 'cpp11::writable::r_vector<double>::iterator' cannot be assigned because its copy assignment operator is implicitly deleted
 1408 |         _It = _STD forward<_UIter>(_UIt);
      |             ^
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.40.33807\include\algorithm:3556:10: note: in instantiation of function template specialization 'std::_Seek_wrapped<cpp11::writable::r_vector<double>::iterator, cpp11::writable::r_vector<double>::iterator &>' requested here
 3556 |     _STD _Seek_wrapped(_Dest, _UDest);
      |          ^
D:/bld/r-arrow_1721706669778/_h_env/lib/R/library/cpp11/include\cpp11/doubles.hpp:149:10: note: in instantiation of function template specialization 'std::transform<cpp11::r_vector<int>::const_iterator, cpp11::writable::r_vector<double>::iterator, (lambda at D:\bld\r-arrow_1721706669778\_h_env\lib\R\library\cpp11\include\cpp11\doubles.hpp:149:55)>' requested here
  149 |     std::transform(xn.begin(), xn.end(), ret.begin(), [](int value) {
      |          ^
D:/bld/r-arrow_1721706669778/_h_env/lib/R/library/cpp11/include\cpp11/r_vector.hpp:263:21: note: copy assignment operator of 'iterator' is implicitly deleted because field 'data_' is of reference type 'const r_vector<double> &'
  263 |     const r_vector& data_;
      |                     ^

whereas libc++ and libstdc++ don't?

I'm not 100% certain that this is the right analysis, but at least I've checked that our windows builds (despite all the infra updates, new R versions & new compilers) builds with 0.4.3, so it would be great if this could somehow be fixed (as indefinitely staying on an old version is bound to lead to other problems).

[DavisVaughan]

Thanks for digging in. I'm planning a patch release in the next 2-3 weeks, I'll try and get a patch for this in too. I'll probably need you or someone else to verify the PR works once I make it!

[h-vetinari]

Happy to help with testing if there's a new version!