CFI: download LLVM Gold plugin, if requested by env var or GYP_DEFINES.

tools/clang/scripts/update.sh

 #!/usr/bin/env bash
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This script will check out llvm and clang into third_party/llvm and build it.
 
 # Do NOT CHANGE this if you don't know what you're doing -- see
 # https://code.google.com/p/chromium/wiki/UpdatingClang
 # Reverting problematic clang rolls is safe, though.
@@ skipping 35 matching lines @@
 if [[ -z "$GYP_DEFINES" ]]; then
   GYP_DEFINES=
 fi
 if [[ -z "$GYP_GENERATORS" ]]; then
   GYP_GENERATORS=
 fi
 if [[ -z "$LLVM_DOWNLOAD_GOLD_PLUGIN" ]]; then
   LLVM_DOWNLOAD_GOLD_PLUGIN=
 fi
 
+if [[ "$GYP_DEFINES" =~ .*cfi_vptr=1.* ]] || \

[hans, 2015/10/09 21:42:48]

Doesn't this still need to be guarded by "if Linux ..."?

[krasin, 2015/10/09 21:50:18]

Done.

+   [[ "$GYP_DEFINES" =~ .*buildtype=Official.* ]] || \
+   [[ "$GYP_DEFINES" =~ .*branding=Chrome.* ]] ; then

[Nico, 2015/10/09 21:40:10]

Let's do the same as
https://code.google.com/p/chromium/codesearch#chromium/src/build/linux/sysroo...
and only do this if the latter 2 are both true; drop the first

[krasin, 2015/10/09 21:50:18]

Done.

+  # LLVM Gold plugin is required to build with this configuration.
+  LLVM_DOWNLOAD_GOLD_PLUGIN=1
+fi
 
 # Die if any command dies, error on undefined variable expansions.
 set -eu
 
 
 if [[ -n ${LLVM_FORCE_HEAD_REVISION:-''} ]]; then
   # Use a real revision number rather than HEAD to make sure that the stamp file
   # logic works.
   CLANG_REVISION=$(svn info "$LLVM_REPO_URL" \
       | grep 'Revision:' | awk '{ printf $2; }')
@@ skipping 162 matching lines @@
 fi
 
 
 # Check if there's anything to be done, exit early if not.
 if [[ -f "${STAMP_FILE}" ]]; then
   PREVIOUSLY_BUILT_REVISON=$(cat "${STAMP_FILE}")
   if [[ -z "$force_local_build" ]] && \
        [[ "${PREVIOUSLY_BUILT_REVISON}" = \
           "${PACKAGE_VERSION}" ]]; then
     echo "Clang already at ${PACKAGE_VERSION}"
-    exit 0
+    if [[ -z "${LLVM_DOWNLOAD_GOLD_PLUGIN}" ]] || \
+       [[ -f "${LLVM_BUILD_DIR}/lib/LLVMgold.so" ]]; then

[Nico, 2015/10/09 21:40:10]

with this setup it can theoretically happen that an old LLVMgold plugin happens
to be around. if that turns out to be a problem, I suppose we could have another
stamp file for the plugin, but I think this is fine as-is for nmow.

[krasin, 2015/10/09 21:50:18]

I raised this point, Hans correctly pointed out that we delete the whole
directory, if a new version of Clang is downloaded (including the plugin):
https://codereview.chromium.org/1373043003/#msg13

[Nico, 2015/10/09 21:52:37]

Smart guy, that Hans!

+      exit 0
+    fi
   fi
 fi
 # To always force a new build if someone interrupts their build half way.
 rm -f "${STAMP_FILE}"
 
 
 if [[ -z "$force_local_build" ]]; then
   # Check if there's a prebuilt binary and if so just fetch that. That's faster,
   # and goma relies on having matching binary hashes on client and server too.
   CDS_FILE="clang-${PACKAGE_VERSION}.tgz"
@@ skipping 413 matching lines @@
   # Run Chrome tool tests.
   ninja -C "${LLVM_BUILD_DIR}" cr-check-all
 fi
 if [[ -n "$run_tests" ]]; then
   # Run the LLVM and Clang tests.
   ninja -C "${LLVM_BUILD_DIR}" check-all
 fi
 
 # After everything is done, log success for this revision.
 echo "${PACKAGE_VERSION}" > "${STAMP_FILE}"