|author||Nico Weber <firstname.lastname@example.org>||Thu Nov 07 13:14:37 2019 -0500|
|committer||Commit Bot <email@example.com>||Thu Nov 07 19:51:09 2019 +0000|
win: Only use ICF and LTO if explicitly opted in. The bots pass --use-icf and --use-lto, so it doesn't affect them. Makes the Windows build more like the non-Windows build, and makes incremental build times (== local dev) in the default build config 20x faster. (It also makes it possible to set CC/CXX to clang-cl without getting warnings about /GL, but that's not my motivation here. But I might want to use goma to build gn in the future, at least on my laptop, and then that'll come in handy.) Also add /Zc:inline to cflags in release builds on Windows. Also change non-Win to use LTO only in release builds -- LTO in debug builds doesn't make much sense. Release build times (always `ninja -C out`, i.e. linking both gn.exe and gn_unittests.exe): With this patch: Full: 4m25s Touch just src\gn\command_analyze.cc: 3.8s Size of out\: 844 MB Peak memory use during build: 250 MB With this patch but no /Zc:inline: Full: 4m25s Touch just src\gn\command_analyze.cc: 4.8s Size of out\: 1.05 GB Peak memory use during build: 345 MB Without this patch (== this patch with --use-icf --use-lto; /Zc:inline seems to have no effect when used with /GL): Full: 4m33s Touch just src\gn\command_analyze.cc: 1m55s (!) Size of out\: 1.52 GB Peak memory use during build: 678 MB Change-Id: Idd87389c7537828fe6523a64de6031f9cbbc0fc6 Reviewed-on: https://gn-review.googlesource.com/c/gn/+/6442 Reviewed-by: Scott Graham <firstname.lastname@example.org> Commit-Queue: Nico Weber <email@example.com>
GN is a meta-build system that generates build files for Ninja.
Alternatively, you can build GN from source:
git clone https://gn.googlesource.com/gn cd gn python build/gen.py ninja -C out # To run tests: out/gn_unittests
On Windows, it is expected that
lib.exe can be found in
PATH, so you'll want to run from a Visual Studio command prompt, or similar.
On Linux and Mac, the default compiler is
clang++, a recent version is expected to be found in
PATH. This can be overridden by setting
There is a simple example in examples/simple_build directory that is a good place to get started with the minimal configuration.
For a maximal configuration see the Chromium setup:
and the Fuchsia setup:
If you find a bug, you can see if it is known or report it in the bug database.
GN uses Gerrit for code review. The short version of how to patch is:
Register at https://gn-review.googlesource.com. ... edit code ... ninja -C out && out/gn_unittests
Then, to upload a change for review:
git commit git cl upload --gerrit
When revising a change, use:
git commit --amend git cl upload --gerrit
which will add the new changes to the existing code review, rather than creating a new one.
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You may ask questions and follow along with GN‘s development on Chromium’s gn-dev@ Google Group.