anchor.diff:  make
   
   # use latest available `apt-cache search gcc-` or `clang-`
  +# wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key|sudo apt-key add -
  +# sudo add-apt-repository 'deb http://apt.llvm.org/jammy/ llvm-toolchain-jammy-15 main'
  +# sudo apt-get install clang-15
  +
   cd ~/build/R-devel-strict-clang
  -./configure --without-recommended-packages --disable-byte-compiled-packages --enable-strict-barrier --disable-long-double CC="clang-11 -fsanitize=undefined,address -fno-sanitize=float-divide-by-zero -fno-omit-frame-pointer"
  +./configure --without-recommended-packages --disable-byte-compiled-packages --enable-strict-barrier --disable-long-double CC="clang-15 -fsanitize=undefined,address -fno-sanitize=float-divide-by-zero -fno-sanitize=alignment -fno-omit-frame-pointer" CFLAGS="-g -O3 -Wall -pedantic"
   make
   
   cd ~/build/R-devel-strict-gcc
  
positive.code: alias Rdevel-strict-clang='~/build/R-devel-strict-clang/bin/R --vanilla'
  
  cd ~/GitHub/data.table
  Rdevel-strict-gcc CMD INSTALL data.table_1.14.1.tar.gz
  Rdevel-strict-clang CMD INSTALL data.table_1.14.1.tar.gz
  # Check UBSAN and ASAN flags appear in compiler output above. Rdevel was compiled with them so should be passed through to here
  Rdevel-strict-gcc
  Rdevel-strict-clang  # repeat below with clang and gcc
  isTRUE(.Machine$sizeof.longdouble==0)  # check noLD is being tested
  options(repos = "http://cloud.r-project.org")
  install.packages(c("bit64","xts","nanotime","R.utils","yaml")) # minimum packages needed to not skip any tests in test.data.table()
  # install.packages(c("curl","knitr"))                          # for `R CMD check` when not strict. Too slow to install when strict
  require(data.table)
  test.data.table(script="*.Rraw") # 7 mins (vs 1min normally) under UBSAN, ASAN and --strict-barrier
                                   # without the fix in PR#3515, the --disable-long-double lumped into this build does now work and correctly reproduces the noLD problem
  
negative.code: wget -N https://stat.ethz.ch/R/daily/R-devel.tar.gz
  rm -rf R-devel
  rm -rf R-devel-strict-*
  tar xf R-devel.tar.gz
  mv R-devel R-devel-strict-gcc
  tar xf R-devel.tar.gz
  mv R-devel R-devel-strict-clang
  tar xf R-devel.tar.gz
  
  sudo apt-get -y build-dep r-base
  cd R-devel  # may be used for revdep testing: .dev/revdep.R.
  