Explicitly call abs as a function in DataFrame.h

[xhochy]

When building with clang (in this case on Windows), the call to abs is expanded to the vectorised form although we call it with a scalar value. Explicitly requesting std::abs prohibits this expansion.

For reference, the original error:

/C/Users/Administrator/miniconda3/conda-bld/r-arrow_1586848759312/_h_env/Library/bin/clang++.exe  -std=gnu++14 -I"C:/Users/Administrator/miniconda3/conda-bld/r-arrow_1586848759312/_h_env/lib/R/include" -D
NDEBUG -DNDEBUG -I"%BUILD_PREFIX%\Library/include" -I"%BUILD_PREFIX%/include" -O2 -D_CRT_SECURE_NO_WARNINGS -DARROW_R_WITH_ARROW -fuse-ld=lld -I"C:/Users/Administrator/miniconda3/conda-bld/r-arrow_1586848
759312/_h_env/Lib/R/library/Rcpp/include"   -I"C:/Users/Administrator/miniconda3/conda-bld/r-arrow_1586848759312/_h_env/lib/R/../../Library/mingw-w64/include"     -O2 -Wall -gdwarf-2 -march=x86-64 -mtune=
generic -c recordbatch.cpp -o recordbatch.o
In file included from recordbatch.cpp:18:
In file included from ././arrow_types.h:145:
In file included from C:/Users/Administrator/miniconda3/conda-bld/r-arrow_1586848759312/_h_env/Lib/R/library/Rcpp/include\Rcpp.h:57:
C:/Users/Administrator/miniconda3/conda-bld/r-arrow_1586848759312/_h_env/Lib/R/library/Rcpp/include\Rcpp/DataFrame.h:82:24: error: no matching function for call to 'abs'
                return abs(INTEGER(rn)[1]);
                       ^~~
recordbatch.cpp:100:47: note: in instantiation of member function 'Rcpp::DataFrame_Impl<PreserveStorage>::nrow' requested here
  return arrow::RecordBatch::Make(schema, tbl.nrow(), std::move(arrays));
                                              ^
C:/Users/Administrator/miniconda3/conda-bld/r-arrow_1586848759312/_h_env/Lib/R/library/Rcpp/include\Rcpp/sugar/functions/math.h:42:19: note: candidate function not viable: no known conversion from 'int'
      to 'SEXP' (aka 'SEXPREC *') for 1st argument
VECTORIZED_MATH_1(abs,::fabs)
                  ^
C:/Users/Administrator/miniconda3/conda-bld/r-arrow_1586848759312/_h_env/Lib/R/library/Rcpp/include\Rcpp/sugar/block/Vectorized_Math.h:91:9: note: expanded from macro 'VECTORIZED_MATH_1'
        __NAME__( SEXP x){ return __NAME__( NumericVector( x ) ) ; }             \
        ^
C:/Users/Administrator/miniconda3/conda-bld/r-arrow_1586848759312/_h_env/Lib/R/library/Rcpp/include\Rcpp/sugar/functions/math.h:42:19: note: candidate template ignored: could not match
      'VectorBase<14, NA, type-parameter-0-1>' against 'int'
C:/Users/Administrator/miniconda3/conda-bld/r-arrow_1586848759312/_h_env/Lib/R/library/Rcpp/include\Rcpp/sugar/functions/math.h:42:19: note: candidate template ignored: could not match
      'VectorBase<13, NA, type-parameter-0-1>' against 'int'
1 error generated.
make: *** [recordbatch.o] Error 1C:/Users/Administrator/miniconda3/conda-bld/r-arrow_1586848759312/_h_env/lib/R/etc/x64/Makeconf:215: recipe for target 'recordbatch.o' failed

Checklist

• Code compiles correctly
• R CMD check still passes all tests
• Prefereably, new tests were added which fail without the change
• Document the changes by file in ChangeLog

[eddelbuettel]

Thanks, that looks a valid catch. We generally tried to be explicit but in a large enough code base...

[eddelbuettel]

Out of curiousity where/why/how would you build with clang on Windoze, and how is the cooperation with Rtools going?

[xhochy]

Out of curiousity where/why/how would you build with clang on Windoze, and how is the cooperation with Rtools going?

I'm trying to the Apache Arrow libraries on Windows for R and Python with using the same Arrow C++ arrow.dll. This has been quite adventurous as they use different toolchains (MSVC for the Python world and MinGW in the RTools setting). By building the C++ part of the R Arrow package with clang, I was able to link (using lld) against the MSVC-based arrow.dll and the MinGW-based R world. Tests run smoothly for now. I'll try to write a blog post if this really works stable.

[eddelbuettel]

I tried / had to try similar gymnastics in the past when shepherding projects at workplaces relying on vendor-supplied DLLs. It is generally ... a nightmare and I am quite content to not work on Windows that much anymore. And Python/R interop always was a huge challenge there for the reason you nailed down: two different toolchains. If you were to reliably bridge that it would be a huge deal.

The official Rcpp statement on this is in the Rcpp FAQ and could be shortened to don't bother ... But keep us posted.

[eddelbuettel]

BTW @xhochy the old (Emacs et al standard) ChangeLog format has two spaces around the name:

modified   ChangeLog
@@ -1,4 +1,4 @@
-2020-04-15 Uwe Korn <mail@uwekorn.com>
+2020-04-15  Uwe Korn  <mail@uwekorn.com>
 
 	* inst/include/Rcpp/DataFrame.h: Explicit call to scalar std::abs

Just in case you ever feel compelled to send another PR with a ChangeLog entry. Appreciate you put one in. Greetings from an ex-Karlsruher...