Chromium ships a prebuilt clang binary. It's just upstream clang built at a known-good revision that we bump every two weeks or so.
This is the only supported compiler for building Chromium.
is_clang = false will make the build use system gcc on Linux. There are no bots that test this and there is no guarantee it will work, but we accept patches for this configuration.
The chromium style plugin is used by default when clang is used.
If you're working on the plugin, you can build it locally like so:
./tools/clang/scripts/build.py --without-androidto build the plugin.
ninja -C third_party/llvm-build/Release+Asserts/to build incrementally.
To test the FindBadConstructs plugin, run:
(cd tools/clang/plugins/tests && \ ./test.py ../../../../third_party/llvm-build/Release+Asserts/bin/clang \ ../../../../third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.so)
Since the plugin is rolled with clang changes, behavior changes to the plugin should be guarded by flags to make it easy to roll clang. A general outline:
GNand verify the new behavior.
clang is the default compiler on Windows. It uses MSVC's SDK, so you still need to have Visual Studio with C++ support installed.
clang_base_path in your args.gn to the llvm build directory containing
bin/clang (i.e. the directory you ran cmake). This must be an absolute path. You also need to disable chromium's clang plugin.
Here's an example that also disables debug info and enables the component build (both not strictly necessary, but they will speed up your build):
clang_base_path = getenv("HOME") + "/src/llvm-build" clang_use_chrome_plugins = false is_debug = false symbol_level = 1 is_component_build = true
On Windows, for
clang_base_path use something like this instead:
clang_base_path = "c:/src/llvm-build"
You can then look in
out/gn/toolchain.ninja and check that the
rule cc and
rule cxx commands run your clang binary. If things look good, run
ninja -C out/gn to build.
Chromium tries to be buildable with its currently pinned clang, and with clang trunk. Set
llvm_force_head_revision = true in your args.gn if the clang you‘re trying to build with is closer to clang trunk than to Chromium’s pinned clang (which
tools/clang/scripts/update.py --print-revision prints).
Toolchain support gives an overview of clang rolls, and documents when to revert clang rolls and how to file good toolchain bugs.
Updating clang documents the mechanics of updating clang, and which files are included in the default clang package.
Clang Sheriffing contains instructions for how to debug compiler bugs, for clang sheriffs.