configure

#!/bin/sh

: "${R_HOME:=$(R RHOME)}"
R="${R_HOME}/bin/R"

CXX=$("${R}" CMD config CXX20)
CXXSTD=$("${R}" CMD config CXX20STD)
CXXFLAGS=$("${R}" CMD config CXX20FLAGS)

if test -z "${CXX}"; then
  CXX=$("${R}" CMD config CXX)
  CXXSTD=$("${R}" CMD config CXXSTD)
  CXXFLAGS=$("${R}" CMD config CXXFLAGS)
fi

CPPFLAGS=$("${R}" CMD config CPPFLAGS)
LDFLAGS=$("${R}" CMD config LDFLAGS)

cat > conftest.cpp <<'EOF'
#include <atomic>
#include <cstddef>

struct State {
  std::size_t pos;
  std::size_t end;
};

int main() {
  std::atomic<State> state;
  State old_state{0, 0};
  State new_state{1, 1};
  state.compare_exchange_weak(old_state, new_state);
  return 0;
}
EOF

try_link() {
  ${CXX} ${CXXSTD} ${CPPFLAGS} ${CXXFLAGS} conftest.cpp ${LDFLAGS} "$1" -o conftest >/dev/null 2>&1
}

LIBATOMIC=
if try_link ""; then
  :
elif try_link "-latomic"; then
  LIBATOMIC=" -latomic"
else
  echo "configure: WARNING: could not link C++ atomic compare/exchange test" >&2
fi

rm -rf conftest conftest.cpp conftest.dSYM

sed "s|@LIBATOMIC@|${LIBATOMIC}|g" src/Makevars.in > src/Makevars