[CMake] [PATCH] bootstrap: Detect known C/C++ compiler toolchains

[Brad King]

Look for a C/C++ compiler pair from known toolchains on some platforms.
This makes it less likely that mismatched compilers will be found.
Check only if the environment variables CC and CXX are both empty.
---

Todd Gamblin wrote:
> 1. Bootstrap script doesn't seem to work quite right on the frontend.
> 
> Building CMake was a bit hairy on the Power6 front end node on our
> BlueGene systems.  The machine runs Linux and has both GNU and IBM XL
> toolchains for the frontend itself.  The CMake bootstrap script detected
> cc for the C compiler and xlC for the C++ compiler, and linking failed
> on something 50% through the build because it was passing -dynamic to
> xlC, which is the wrong flag.  It would be nice if CMake would prefer
> one or the other tool chain.

Please try this patch on the Power6 front-end to your BlueGene.
It should prefer matching compiler pairs first.

-Brad

 bootstrap |   71 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 69 insertions(+), 2 deletions(-)

diff --git a/bootstrap b/bootstrap
index 1687776..01d9e15 100755
--- a/bootstrap
+++ b/bootstrap
@@ -650,11 +650,74 @@ if ${cmake_system_haiku}; then
   cmake_ld_flags="${LDFLAGS} -lroot -lbe"
 fi
 
+#-----------------------------------------------------------------------------
+# Detect known toolchains on some platforms.
+cmake_toolchains=''
+case "${cmake_system}" in
+  *AIX*)   cmake_toolchains='XL GNU' ;;
+  *CYGWIN*) cmake_toolchains='GNU' ;;
+  *Darwin*) cmake_toolchains='GNU Clang' ;;
+  *Linux*) cmake_toolchains='GNU Clang XL PGI PathScale' ;;
+  *MINGW*) cmake_toolchains='GNU' ;;
+esac
+
+# Toolchain compiler name table.
+cmake_toolchain_Clang_CC='clang'
+cmake_toolchain_Clang_CXX='clang++'
+cmake_toolchain_GNU_CC='gcc'
+cmake_toolchain_GNU_CXX='g++'
+cmake_toolchain_PGI_CC='pgcc'
+cmake_toolchain_PGI_CXX='pgCC'
+cmake_toolchain_PathScale_CC='pathcc'
+cmake_toolchain_PathScale_CXX='pathCC'
+cmake_toolchain_XL_CC='xlc'
+cmake_toolchain_XL_CXX='xlC'
+
+cmake_toolchain_try()
+{
+  tc="$1"
+  TMPFILE=`cmake_tmp_file`
+
+  eval "tc_CC=\${cmake_toolchain_${tc}_CC}"
+  echo 'int main() { return 0; }' > "${TMPFILE}.c"
+  cmake_try_run "$tc_CC" "" "${TMPFILE}.c" >> cmake_bootstrap.log 2>&1
+  tc_result_CC="$?"
+  rm -f "${TMPFILE}.c"
+  test "${tc_result_CC}" = "0" || return 1
+
+  eval "tc_CXX=\${cmake_toolchain_${tc}_CXX}"
+  echo 'int main() { return 0; }' > "${TMPFILE}.cpp"
+  cmake_try_run "$tc_CXX" "" "${TMPFILE}.cpp" >> cmake_bootstrap.log 2>&1
+  tc_result_CXX="$?"
+  rm -f "${TMPFILE}.cpp"
+  test "${tc_result_CXX}" = "0" || return 1
+
+  cmake_toolchain="$tc"
+}
+
+cmake_toolchain_detect()
+{
+  cmake_toolchain=
+  for tc in ${cmake_toolchains}; do
+    echo "Checking for $tc toolchain" >> cmake_bootstrap.log 2>&1
+    cmake_toolchain_try "$tc" &&
+    echo "Found $tc toolchain" &&
+    break
+  done
+}
+
+if [ -z "${CC}" -a -z "${CXX}" ]; then
+  cmake_toolchain_detect
+fi
+
+#-----------------------------------------------------------------------------
 # Test C compiler
 cmake_c_compiler=
 
 # If CC is set, use that for compiler, otherwise use list of known compilers
-if [ -n "${CC}" ]; then
+if [ -n "${cmake_toolchain}" ]; then
+  eval cmake_c_compilers="\${cmake_toolchain_${cmake_toolchain}_CC}"
+elif [ -n "${CC}" ]; then
   cmake_c_compilers="${CC}"
 else
   cmake_c_compilers="${CMAKE_KNOWN_C_COMPILERS}"
@@ -697,13 +760,16 @@ See cmake_bootstrap.log for compilers attempted.
 fi
 echo "C compiler on this system is: ${cmake_c_compiler} ${cmake_c_flags}"
 
+#-----------------------------------------------------------------------------
 # Test CXX compiler
 cmake_cxx_compiler=
 
 # On Mac OSX, CC is the same as cc, so make sure not to try CC as c++ compiler.
 
 # If CC is set, use that for compiler, otherwise use list of known compilers
-if [ -n "${CXX}" ]; then
+if [ -n "${cmake_toolchain}" ]; then
+  eval cmake_cxx_compilers="\${cmake_toolchain_${cmake_toolchain}_CXX}"
+elif [ -n "${CXX}" ]; then
   cmake_cxx_compilers="${CXX}"
 else
   cmake_cxx_compilers="${CMAKE_KNOWN_CXX_COMPILERS}"
@@ -754,6 +820,7 @@ See cmake_bootstrap.log for compilers attempted."
 fi
 echo "C++ compiler on this system is: ${cmake_cxx_compiler} ${cmake_cxx_flags}"
 
+#-----------------------------------------------------------------------------
 # Test Make
 
 cmake_make_processor=
-- 
1.7.0