install.sh: Adopt LLVM as the default/preferred compilers

.github/workflows/build.yml

@@ -25,23 +25,27 @@ jobs:
             version: 22
             network: smp
             native_multi_image: 1
+            brew_via_install: 1
             FFLAGS: -fcoarray
           - os: macos-15
             compiler: flang
             version: 22
             network: smp
+            brew_via_install: 1
             native_multi_image: 1
             FFLAGS: -fcoarray
           - os: macos-15-intel
             compiler: flang
             version: 22
             network: smp
+            brew_via_install: 1
             native_multi_image: 1
             FFLAGS: -fcoarray
           - os: macos-26
             compiler: flang
             version: 22
             network: smp
+            brew_via_install: 1
             native_multi_image: 1
             FFLAGS: -fcoarray
 
@@ -177,7 +181,7 @@ jobs:
         echo "CXX=g++-${COMPILER_VERSION}" >> "$GITHUB_ENV"
 
     - name: Set flang variables
-      if: matrix.compiler == 'flang'
+      if: ${{ matrix.compiler == 'flang' && !matrix.brew_via_install }}
       run: |
         set -x
         echo "FC=flang-new" >> "$GITHUB_ENV" 
@@ -239,15 +243,15 @@ jobs:
         apt install -y build-essential pkg-config make git curl
 
     - name: Install macOS Dependencies
-      if: contains(matrix.os, 'macos')
+      if: ${{ contains(matrix.os, 'macos') && !matrix.brew_via_install }}
       run: |
         set -x
         brew update
         # fpm binary distribution for macOS requires gfortran shared libraries from gcc@12
         brew install gcc@12
 
     - name: Install LLVM flang on macOS
-      if: contains(matrix.os, 'macos') && matrix.compiler == 'flang'
+      if: ${{ contains(matrix.os, 'macos') && matrix.compiler == 'flang' && !matrix.brew_via_install }}
       run: |
         set -x
         brew install llvm@${COMPILER_VERSION} flang
@@ -258,6 +262,7 @@ jobs:
         echo "PATH=$(brew --prefix)/opt/llvm/bin:${PATH}" >> "$GITHUB_ENV"
 
     - name: Setup FPM
+      if: ${{ !matrix.brew_via_install }}
       uses: fortran-lang/setup-fpm@main
       with:
         github-token: ${{ secrets.GITHUB_TOKEN }}
@@ -283,7 +288,9 @@ jobs:
         echo
         echo PATH="$PATH"
         for tool in ${FC} ${CC} ${CXX} fpm ; do
-          ( echo ; set -x ; w=$(which $tool) ; ls -al $w ; ls -alhL $w ; $tool --version )
+          if command -v $tool > /dev/null 2>&1 ; then
+            ( echo ; set -x ; w=$(which $tool) ; ls -al $w ; ls -alhL $w ; $tool --version )
+          fi
         done
 
     - name: Build Caffeine (install.sh)

README.md

@@ -50,9 +50,7 @@ Prerequisites & Dependencies
 ### Build prerequisites
 The `install.sh` script uses the following packages:
 * Fortran and C compilers
-    * We regularly test with: GNU Fortran versions 13, 14, 15 and LLVM Flang versions 19, 20, 21
-    * On macOS the Homebrew-installed `llvm` and `flang` packages may require some
-      additional settings, see [issue #228](https://github.com/BerkeleyLab/caffeine/issues/228) for the latest information.
+    * We regularly test with: LLVM Flang versions 19:22 and GNU Fortran versions 13:15
 * [Fortran package manager] `fpm`
 * [pkg-config]
 * [realpath]
@@ -98,7 +96,10 @@ env FC=<Fortran-compiler> CC=<C-compiler> CXX=<C++-compiler> ./install.sh <optio
 env CAF_IMAGES=8 ./run-fpm.sh run --example hello
 ```
 
-The provided compilers MUST be "compatible": for the best experience you are
+If `$FC` or `$CC` are unset, then `install.sh` will look for LLVM-based compilers in
+the `PATH`, and failing that, offer to install such compilers using Homebrew.
+
+The selected compilers MUST be "compatible": for the best experience you are
 HIGHLY recommended to specify the language frontends provided by a single version
 of a given compiler suite installation. The C++ compiler is optional for
 single-node deployments (and can be disabled using command-line option `--without-cxx`), 
@@ -107,10 +108,9 @@ but C++ is required for some network backends.
 *Note for macOS/Homebrew users*: Homebrew may be used to install
 [LLVM flang](https://formulae.brew.sh/formula/flang) for use with Caffeine, however
 by default Homebrew will not replace the incompatible Apple-provided `clang` in your `PATH`.
-Such users are recommended to use Homebrew's version-suffixed compiler variants, 
-for example setting `FC=flang-21 CC=clang-21 CXX=clang++-21` in the command above,
+Such users are recommended to use Homebrew's matching LLVM C/C++ compilers
+(usually installed in `/opt/homebrew/opt/llvm/bin`)
 to ensure that a matching set of LLVM compilers are used. 
-See also [issue #228](https://github.com/BerkeleyLab/caffeine/issues/228).
 
 The `install.sh` recognizes a number of command-line options and environment variables to
 customize behavior for your system. See the output of `./install.sh --help` for full documentation,

install.sh

@@ -45,11 +45,11 @@ Report bugs to fortran@lbl.gov or at https://go.lbl.gov/caffeine
 EOF
 }
 
-GCC_VERSION=${GCC_VERSION:=14}
 GASNET_VERSION="stable"
 VERBOSE=""
 GASNET_CONDUIT="${GASNET_CONDUIT:-smp}"
 YES=false
+APPEND_CFLAGS=""
 
 list_prerequisites()
 {
@@ -58,7 +58,7 @@ Caffeine and this installer were developed with the following prerequisites.
 If any are missing and if permission is granted, the installer will install
 the latest versions using Homebrew:
 
-  GCC $GCC_VERSION
+  LLVM flang
   GASNet-EX $GASNET_VERSION
   fpm
   git (used by fpm to clone dependencies)
@@ -115,23 +115,57 @@ while [ "$1" != "" ]; do
     shift
 done
 
-set -u # error on use of undefined variable
+# Early check for pre-installed Homebrew
+BREW="${BREW:-brew}"
+if command -v "$BREW" > /dev/null 2>&1; then
+  BREW_PREFIX=`$BREW --prefix || exit 0`
+  if [ -z ${BREW_PREFIX:+x} ] || [ ! -d "$BREW_PREFIX" ] ; then
+    echo Warning: Failed to detect Homebrew prefix
+    BREW_PREFIX=
+  fi
+fi
 
-if [ -z ${FC+x} ] || [ -z ${CC+x} ] || [ -z ${CXX+x} ]; then
-  if command -v gfortran-$GCC_VERSION > /dev/null 2>&1; then
-    FC=`which gfortran-$GCC_VERSION`
+if [ -z ${FC:+x} ] || [ -z ${CC:+x} ]; then
+  if command -v flang > /dev/null 2>&1; then
+    FC=`which flang`
     echo "Setting FC=$FC"
+    if [ -n "$BREW_PREFIX" ] && [[ $FC =~ $BREW_PREFIX ]] ; then
+      # We are using Homebrew flang, so prefer Homebrew clang/clang++
+      export PATH="$BREW_PREFIX/opt/llvm/bin:$PATH"
+    fi
   fi
-  if command -v gcc-$GCC_VERSION > /dev/null 2>&1; then
-    CC=`which gcc-$GCC_VERSION`
+  if command -v clang > /dev/null 2>&1; then
+    CC=`which clang`
     echo "Setting CC=$CC"
   fi
-  if command -v g++-$GCC_VERSION > /dev/null 2>&1; then
-    CXX=`which g++-$GCC_VERSION`
+fi
+if [ -n "$CC" ] && ! command -v "$CC" > /dev/null 2>&1; then
+  echo "CC=$CC not found. If you don't yet have a C compiler, please leave environment variable CC unset."
+  exit 1
+fi
+if [ -n "$FC" ] && ! command -v "$FC" > /dev/null 2>&1; then
+  echo "FC=$FC not found. If you don't yet have a Fortran compiler, please leave environment variable FC unset."
+  exit 1
+fi
+if [ -z ${CXX:+x} ] && [ -n "$CC" ] ; then 
+  # C++ is an optional dependency
+  # try to auto-detect from CC
+  if [[ $(basename $CC) =~ clang ]] ; then 
+    CXX_guess=clang++
+  else
+    CXX_guess=g++
+  fi
+  if [[ $CC =~ (-[0-9]+)$ ]] ; then 
+    CXX_guess=${CXX_guess}${BASH_REMATCH[0]} 
+  fi
+  if command -v $CXX_guess > /dev/null 2>&1; then
+    CXX=`which $CXX_guess`
     echo "Setting CXX=$CXX"
   fi
 fi
 
+set -u # error on use of undefined variable
+
 if command -v pkg-config > /dev/null 2>&1; then
   PKG_CONFIG=`which pkg-config`
 fi
@@ -163,7 +197,7 @@ ask_permission_to_use_homebrew()
 {
   cat << EOF
 
-Either one or more of the environment variables FC, CC, and CXX are unset or
+Either one or more of the environment variables FC and CC are unset or
 one or more of the following packages are not in the PATH: pkg-config, realpath, make, fpm.
 If you grant permission to install prerequisites, you will be prompted before each installation.
 
@@ -212,9 +246,9 @@ exit_if_user_declines()
     case ${1:-} in  
       *GASNet*) 
         echo "Please ensure the $pkg.pc file is in $PKG_CONFIG_PATH and then rerun './install.sh'." ;;
-      *GCC*) 
-        echo "To use compilers other than Homebrew-installed gcc-$GCC_VERSION, g++-$GCC_VERSION, and gfortran-$GCC_VERSION,"
-        echo "please set the FC, CC, and CXX environment variables and rerun './install.sh'." ;;
+      *FC*) 
+        echo "To use compilers other than Homebrew-installed LLVM flang and clang,"
+        echo "please set the FC and CC environment variables and rerun './install.sh'." ;;
       *) 
         echo "Please ensure that $1 is installed and in your PATH and then rerun './install.sh'." ;;
     esac
@@ -228,13 +262,11 @@ if [ ! -d $DEPENDENCIES_DIR ]; then
   mkdir -p $DEPENDENCIES_DIR
 fi
 
-if [ -z ${FC+x} ] || [ -z ${CC+x} ] || [ -z ${CXX+x} ] || [ -z ${PKG_CONFIG+x} ] || [ -z ${REALPATH+x} ] || [ -z ${MAKE+x} ] || [ -z ${FPM+x} ] ; then
+if [ -z ${FC:+x} ] || [ -z ${CC:+x} ] || [ -z ${PKG_CONFIG:+x} ] || [ -z ${REALPATH:+x} ] || [ -z ${MAKE:+x} ] || [ -z ${FPM:+x} ] ; then
 
   ask_permission_to_use_homebrew 
   exit_if_user_declines "brew"
 
-  BREW="brew"
-
   if ! command -v $BREW > /dev/null 2>&1; then
 
     ask_permission_to_install_homebrew
@@ -264,47 +296,62 @@ EOF
     fi
   fi
 
-  if [ -z ${FC+x} ] || [ -z ${CC+x} ] || [ -z ${CXX+x} ]; then
-    ask_permission_to_install_homebrew_package "gfortran, gcc, and g++" "gcc@$GCC_VERSION" 
-    exit_if_user_declines "GCC"
-    "$BREW" install gcc@$GCC_VERSION
-    if [ uname == "Linux" ]; then
-      brew link --force glibc
-    fi
+  BREW_PREFIX=`$BREW --prefix || exit 0`
+  if [ -z ${BREW_PREFIX:+x} ] || [ ! -d "$BREW_PREFIX" ] ; then
+    echo Failed to detect Homebrew prefix
+    echo 1
   fi
-  CC=`which gcc-$GCC_VERSION`
-  CXX=`which g++-$GCC_VERSION`
-  FC=`which gfortran-$GCC_VERSION`
 
-  if [ -z ${REALPATH+x} ] || [ -z ${MAKE+x} ] ; then
+  # fetch the latest package definitions:
+  $BREW update
+
+  if [ -z ${FC:+x} ] || [ -z ${CC:+x} ] ; then
+    ask_permission_to_install_homebrew_package "'llvm' and 'flang'"
+    exit_if_user_declines "FC"
+    $BREW install llvm flang
+
+    # Homebrew does not inject clang/clang++ into PATH on macOS
+    export PATH="$BREW_PREFIX/opt/llvm/bin:$PATH"
+    CC=`which clang`
+    CXX=`which clang++`
+    FC=`which flang-new`
+    for tool in $CC $CXX $FC ; do
+      if ! command -v $tool > /dev/null 2>&1 ; then
+        echo Failed to detect Homebrew compiler install at $tool
+        exit 1
+      fi
+    done
+  fi
+
+  if [ -z ${REALPATH:+x} ] || [ -z ${MAKE:+x} ] ; then
     ask_permission_to_install_homebrew_package "'realpath' and 'make'" "coreutils"
-    exit_if_user_declines "realpath"
-    "$BREW" install coreutils
+    exit_if_user_declines "realpath and make"
+    $BREW install coreutils
+    REALPATH=`which realpath`
+    MAKE=`which make`
   fi
-  REALPATH=`which realpath`
 
-  if [ -z ${PKG_CONFIG+x} ]; then
+  if [ -z ${PKG_CONFIG:+x} ]; then
     ask_permission_to_install_homebrew_package "'pkg-config'"
     exit_if_user_declines "pkg-config"
-    "$BREW" install pkg-config
+    $BREW install pkg-config
+    PKG_CONFIG=`which pkg-config`
   fi
-  PKG_CONFIG=`which pkg-config`
 
-  if [ -z ${FPM+x} ] ; then
+  if [ -z ${FPM:+x} ] ; then
     ask_permission_to_install_homebrew_package "'fpm'"
     exit_if_user_declines "fpm"
-    "$BREW" tap fortran-lang/hombrew-fortran
-    "$BREW" install fpm
+    $BREW install fpm
+    FPM=`which fpm`
   fi
-  FPM=`which fpm`
 fi
 
 PREFIX=${PREFIX:-"${HOME}/.local"}
 mkdir -p "$PREFIX"
 PREFIX=`$REALPATH "$PREFIX"`
 echo "PREFIX=$PREFIX"
 
-if [ -z ${PKG_CONFIG_PATH+x} ]; then
+if [ -z ${PKG_CONFIG_PATH:+x} ]; then
   PKG_CONFIG_PATH="$PREFIX/lib/pkgconfig"
 else
   PKG_CONFIG_PATH="$PREFIX/lib/pkgconfig:$PKG_CONFIG_PATH"
@@ -317,6 +364,13 @@ if [[ $FPM_FC == *flang* ]]; then
 fi
 FPM_CC="$($REALPATH $(command -v $CC))"
 
+# workaround issue #228: clang cannot find Homebrew flang's C header
+if [ "${BREW_PREFIX:-unset}" != unset ] ; then
+  if [[ $FPM_FC =~ flang ]] && [[ $FPM_FC =~ $BREW_PREFIX ]] ; then
+    APPEND_CFLAGS="-I$(dirname $(find "$BREW_PREFIX/Cellar/flang" -name ISO_Fortran_binding.h | head -1))"
+  fi
+fi
+
 ask_package_permission()
 {
   cat << EOF
@@ -436,7 +490,7 @@ cat << EOF > $CAFFEINE_PC
 CAFFEINE_FPM_LDFLAGS=$GASNET_LDFLAGS $GASNET_LIB_LOCATIONS
 CAFFEINE_FPM_FC=$FPM_FC
 CAFFEINE_FPM_CC=$GASNET_CC
-CAFFEINE_FPM_CFLAGS=$GASNET_CFLAGS $GASNET_CPPFLAGS
+CAFFEINE_FPM_CFLAGS=$GASNET_CFLAGS $GASNET_CPPFLAGS $APPEND_CFLAGS
 Name: caffeine
 Description: Coarray Fortran parallel runtime library
 URL: https://gitlab.lbl.gov/berkeleylab/caffeine