configure

#!/usr/bin/env sh

# Find R compilers
CC=`${R_HOME}/bin/R CMD config CC`
CFLAGS=`${R_HOME}/bin/R CMD config CFLAGS`
# compiler and flags to 'cc' file
echo "CC=${CC}" > inst/cc
echo "CFLAGS=${CFLAGS}" >> inst/cc

# gcc compiler info to output #3291
case $CC in gcc*)
  GCCV=`${CC} -dumpfullversion -dumpversion`
  echo "$CC $GCCV"
esac

# Let's keep this simple. If pkg-config is available, use it. Otherwise print
# the helpful message to aid user if compilation does fail. Note 25 of R-exts:
# "[pkg-config] is available on the machines used to produce the CRAN binary packages"
# This script should pass `checkbashisms` for portability; e.g. CRAN's Solaris 10,
# and R-exts note 24 now suggests 'checkbashisms' as we proposed.

msg=0
NOZLIB=1 # if pkg-config is not available then zlib will be disabled for higher chance of compilation success
pkg-config --version > config.log 2>&1
if [ $? -ne 0 ]; then
  echo "*** pkg-config is not installed."
  msg=1
else
  pkg-config --exists zlib
  if [ $? -ne 0 ]; then
    echo "*** pkg-config is installed but 'pkg-config --exists zlib' did not return 0."
    msg=1
  else
    NOZLIB=0
    lib=`pkg-config --libs zlib`
    cflag=`pkg-config --cflags zlib`
    echo "$lib" | grep -qE '[-]lz($| )' >> config.log
    if [ $? -ne 0 ]; then
      echo "*** pkg-config is installed and 'pkg-config --exists zlib' succeeds but"
      echo "*** 'pkg-config --libs zlib' returns '${lib}' which does not include the standard -lz."
      msg=1
    fi
  fi
fi

if [ $msg -ne 0 ]; then
  echo "*** Compilation will now be attempted and if it works you can ignore this message. In"
  echo "*** particular, this should be the case on Mac where zlib is built in or pkg-config"
  echo "*** is not installed. However, if compilation fails, try 'locate zlib.h zconf.h' and"
  echo "*** ensure the zlib development library is installed :"
  echo "***   deb: zlib1g-dev (Debian, Ubuntu, ...)"
  echo "***   rpm: zlib-devel (Fedora, EPEL, ...)"
  echo "***   There is a zlib in brew for OSX but the built in zlib should work."
  echo "*** Note that zlib is required to compile R itself so you may find the advice in the R-admin"
  echo "*** guide helpful regarding zlib. On Debian/Ubuntu, zlib1g-dev is a dependency of r-base as"
  echo "*** shown by 'apt-cache showsrc r-base | grep ^Build-Depends | grep zlib', and therefore"
  echo "*** 'sudo apt-get build-dep r-base' should be sufficient too."
  echo "*** To silence this message, please ensure that :"
  echo "***   1) 'pkg-config --exists zlib' succeeds (i.e. \$? -eq 0)"
  echo "***   2) 'pkg-config --libs zlib' contains -lz"
  echo "*** Compilation will now be attempted ..."
else
  version=`pkg-config --modversion zlib`
  echo "zlib ${version} is available ok"
fi

# Test if we have a OPENMP compatible compiler
# Aside: ${SHLIB_OPENMP_CFLAGS} does not appear to be defined at this point according to Matt's testing on
# Linux, and R CMD config SHLIB_OPENMP_CFLAGS also returns 'no information for variable'. That's not
# inconsistent with R-exts$1.2.1.1, though, which states it's 'available for use in Makevars' (so not
# necessarily here in configure).
# printf not echo to pass checkbashisms w.r.t. to the \n
# Specifically use schedule(dynamic) to distinguish incompatibilities in OpenMP runtime on macOS, #7318

cat <<EOF > test-omp.c
#ifdef _OPENMP
#include <omp.h>
#endif
void test_openmp(int * result) {
 int sum = 0;
#ifdef _OPENMP
 #pragma omp parallel for reduction(+:sum) num_threads(2) schedule(dynamic)
 for (int i = 1; i <= 2; ++i) sum += i;
#endif
 *result = sum;
}
EOF

test_openmp_variant () {
  # Observed in GitHub Actions: if test_openmp_variant is too fast to compile the next object file,
  # Make (invoked by R CMD SHLIB) will not consider the previous shared object old enough and won't
  # link it anew. --preclean only removes the object files; remove the target as well.
  "${R_HOME}"/bin/Rscript -e 'unlink(paste0("test-omp", .Platform$dynlib.ext))'

  cflags="${PKG_CFLAGS:+${PKG_CFLAGS} }$1"
  libs="${PKG_LIBS:+${PKG_LIBS} }$2"
  printf "%s" "* checking if OpenMP works with CFLAGS='$cflags' LIBS='$libs'... "
  if ! PKG_CFLAGS="$cflags" PKG_LIBS="$libs" "${R_HOME}"/bin/R CMD SHLIB --preclean --clean test-omp.c >>config.log 2>&1; then
    echo "no"
    return 1
  fi

  if ! "${R_HOME}"/bin/Rscript -e '
dll <- paste0("test-omp", .Platform$dynlib.ext)
dyn.load(dll)
ans <- .C("test_openmp", ans = integer(1))$ans
stopifnot(identical(ans, 3L))
' >> config.log 2>&1; then
    echo "no"
    return 1
  fi

  export PKG_CFLAGS="${PKG_CFLAGS} ${1}"
  export PKG_LIBS="${PKG_LIBS} ${2}"
  export R_OPENMP_ENABLED=1
  echo "yes"
  return 0
}

detect_openmp () {
  # OpenMP flags provided in environment variables or specified when configuring R? Does -fopenmp work?
  test_openmp_variant "" "" \
  || test_openmp_variant '$(SHLIB_OPENMP_CFLAGS)' '$(SHLIB_OPENMP_CFLAGS)' \
  || test_openmp_variant -fopenmp -fopenmp \
  && return

  case "$(uname)" in
  Darwin)
    # https://mac.r-project.org/openmp
    test_openmp_variant "-Xclang -fopenmp" "-lomp" && return

    if [ "$(uname -m)" = "arm64" ]; then
      HOMEBREW_PREFIX=/opt/homebrew
    else
      HOMEBREW_PREFIX=/usr/local
    fi
    test -e "${HOMEBREW_PREFIX}/opt/libomp" \
    && test_openmp_variant \
      "-I${HOMEBREW_PREFIX}/opt/libomp/include -Xclang -fopenmp" \
      "-L${HOMEBREW_PREFIX}/opt/libomp/lib -lomp" \
    && return

    if test -e /usr/local/lib/libomp.dylib \
      && test_openmp_variant "-Xclang -fopenmp" "/usr/local/lib/libomp.dylib"; then
      echo "*** Using the OpenMP runtime from /usr/local/lib/libomp.dylib."
      echo "*** Please be careful when mixing the result with CRAN binaries."
      return
    fi

    echo "*** All OpenMP tests failed and you're running macOS."
    echo "*** Do you need an OpenMP runtime from <https://mac.r-project.org/openmp/>?"
    ;;
  esac

  # No support for OpenMP available
  export R_OPENMP_ENABLED=0
}

detect_openmp
# Clean up.
rm -f test-omp.* a.out

if [ "${R_OPENMP_ENABLED}" = "0" ]; then
  echo "***"
  echo "*** OpenMP not supported! data.table uses OpenMP to automatically"
  echo "***   parallelize operations like sorting, grouping, file reading, etc."
  echo "*** For details on how to install the necessary toolchains on your OS see:"
  echo "***   https://github.com/Rdatatable/data.table/wiki/Installation"
  echo "*** Continuing installation without OpenMP support..."
  echo "***"
fi

# retain user supplied PKG_ env variables, #4664. See comments in Makevars.in too.
sed -e "s|@PKG_CFLAGS@|$PKG_CFLAGS|" -e "s|@PKG_LIBS@|$PKG_LIBS|" src/Makevars.in > src/Makevars

# optional dependency on zlib
if [ "$NOZLIB" = "1" ]; then
  echo "*** Compilation without compression support in fwrite"
  sed -e "s|@zlib_cflags@|-DNOZLIB|" src/Makevars > src/Makevars.tmp && mv src/Makevars.tmp src/Makevars
  sed -e "s|@zlib_libs@||" src/Makevars > src/Makevars.tmp && mv src/Makevars.tmp src/Makevars
else
  sed -e "s|@zlib_cflags@|${cflag}|" src/Makevars > src/Makevars.tmp && mv src/Makevars.tmp src/Makevars
  sed -e "s|@zlib_libs@|${lib}|" src/Makevars > src/Makevars.tmp && mv src/Makevars.tmp src/Makevars
fi

exit 0