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|use_lto|use_lto_o2|official_build)=1.* ]]; then

[scottmg, 2015/09/28 22:09:41]

Is "official_build=1" how CrOS does it? On Windows it's `buildtype=Official`.

I've also been burned by this crazy way that compile.py sets official build
https://code.google.com/p/chromium/codesearch#chromium/build/scripts/slave/co...

I don't know if you have to take care of that here or not (probably not since I
guess the bot will set one of the other things you check for above?)

[hans, 2015/09/28 22:11:04]

Seems like a lot of different options :-/ Can you rewrite this so it fits under
80 columns? Maybe a for-loop over them would be cleaner?

Also, should the if-block be Linux-only? I assume we don't want to do this when
official_build=1 on Mac.

[Nico, 2015/10/08 02:27:24]

Yeah, I think you need buildtype=Official (and maybe branding=Chrome)
(https://code.google.com/p/chromium/codesearch#chromium/src/build/linux/sysroo...).

I'd expect that almost nobody uses these other toggles, and those who do know
what to do.

[krasin, 2015/10/09 21:33:51]

Done in https://codereview.chromium.org/1385403006

+  # LLVM Gold plugin is required to build with this configuration

[hans, 2015/09/28 22:11:04]

ultra nit: period at the end of the comment.

[krasin, 2015/10/01 21:07:46]

Done.

+  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 ${PACKAGE_VERSION}"
+    if [[ -n "${LLVM_DOWNLOAD_GOLD_PLUGIN}" ]]; then

[hans, 2015/09/28 22:11:04]

The code below (line 285) already downloads the gold plugin if this variable is
set.

It would be better if the code here just checked if the gold plugin is already
downloaded, and if not skips the exit 0 below. That would correspond nicely to
the comment above: "Check if there's anything to be done, exit early if not."

[krasin, 2015/10/09 21:33:51]

Good idea. Done in https://codereview.chromium.org/1385403006

+      # TODO(krasin): make a stamp for gold plugin to avoid
+      # downloading it every time.
+      ${THIS_DIR}/../../../build/download_gold_plugin.py
+    fi
     exit 0
   fi
 fi
 # To always force a new build if someone interrupts their build half way.
 rm -f "${STAMP_FILE}"
 
 
 if [[ -z "$force_local_build" ]]; then
   # Check if there's a prebuilt binary and if so just fetch that. That's faster,
   # and goma relies on having matching binary hashes on client and server too.
@@ skipping 412 matching lines @@
   # Run Chrome tool tests.
   ninja -C "${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}"