Basic overview

./configure.py generates the build.ninja files used to build ninja. It accepts various flags to adjust build parameters.

The primary build target of interest is ninja, but when hacking on Ninja your changes should be testable so it's more useful to build and run ninja_test when developing.

(./bootstrap.py creates a bootstrap ninja and runs the above process; it‘s only necessary to run if you don’t have a copy of ninja to build with.)

Adjusting build flags

Build in “debug” mode while developing (disables optimizations and builds way faster on Windows):

./configure.py --debug

To use clang, set CXX:

CXX=clang++ ./configure.py

How to successfully make changes to Ninja

Github pull requests are convenient for me to merge (I can just click a button and it‘s all handled server-side), but I’m also comfortable accepting pre-github git patches (via send-email etc.).

Good pull requests have all of these attributes:

  • Are scoped to one specific issue
  • Include a test to demonstrate their correctness
  • Update the docs where relevant
  • Match the Ninja coding style (see below)
  • Don't include a mess of “oops, fix typo” commits

These are typically merged without hesitation. If a change is lacking any of the above I usually will ask you to fix it, though there are obvious exceptions (fixing typos in comments don't need tests).

I am very wary of changes that increase the complexity of Ninja (in particular, new build file syntax or command-line flags) or increase the maintenance burden of Ninja. Ninja is already successfully in use by hundreds of developers for large projects and it already achieves (most of) the goals I set out for it to do. It's probably best to discuss new feature ideas on the mailing list before I shoot down your patch.

Testing

Installing gtest

The ninja_test binary, containing all the tests, depends on the googletest (gtest) library.

  • On older Ubuntus it'll install as libraries into /usr/lib:

      apt-get install libgtest

  • On newer Ubuntus it's only distributed as source

      apt-get install libgtest-dev
  ./configure --with-gtest=/usr/src/gtest

  • Otherwise you need to download it, unpack it, and pass --with-gtest to configure.py. Get it from its downloads page; this direct download link might work too.

Test-driven development

Set your build command to

./ninja ninja_test && ./ninja_test --gtest_filter=MyTest.Name

now you can repeatedly run that while developing until the tests pass (I frequently set it as my compilation command in Emacs). Remember to build “all” before committing to verify the other source still works!

Testing performance impact of changes

If you have a Chrome build handy, it's a good test case. Otherwise, the github downoads page has a copy of the Chrome build files (and depfiles). You can untar that, then run

path/to/my/ninja chrome

and compare that against a baseline Ninja.

There's a script at misc/measure.py that repeatedly runs a command like the above (to address variance) and summarizes its runtime. E.g.

path/to/misc/measure.py path/to/my/ninja chrome

For changing the depfile parser, you can also build parser_perftest and run that directly on some representative input files.

Coding guidelines

Generally it's the Google C++ coding style, but in brief:

  • Function name are camelcase.
  • Member methods are camelcase, expect for trivial getters which are underscore separated.
  • Local variables are underscore separated.
  • Member variables are underscore separated and suffixed by an extra underscore.
  • Two spaces indentation.
  • Opening braces is at the end of line.
  • Lines are 80 columns maximum.
  • All source files should have the Google Inc. license header.

Documentation

Style guidelines

  • Use /// for doxygen.
  • Use \a to refer to arguments.
  • It‘s not necessary to document each argument, especially when they’re relatively self-evident (e.g. in CanonicalizePath(string* path, string* err), the arguments are hopefully obvious)

Building the manual

sudo apt-get install asciidoc --no-install-recommends
./ninja manual

Building the code documentation

sudo apt-get install doxygen
./ninja doxygen

Building for Windows

While developing, it‘s helpful to copy ninja.exe to another name like n.exe; otherwise, rebuilds will be unable to write ninja.exe because it’s locked while in use.

Via Visual Studio

  • Install Visual Studio (Express is fine), Python for Windows, and (if making changes) googletest (see above instructions)
  • In a Visual Studio command prompt: python bootstrap.py

Via mingw on Windows (not well supported)

  • Install mingw, msys, and python
  • In the mingw shell, put Python in your path, and python bootstrap.py
  • To reconfigure, run python configure.py
  • Remember to strip the resulting executable if size matters to you

Via mingw on Linux (not well supported)

  • sudo apt-get install gcc-mingw32 wine
  • export CC=i586-mingw32msvc-cc CXX=i586-mingw32msvc-c++ AR=i586-mingw32msvc-ar
  • ./configure.py --platform=mingw --host=linux
  • Build ninja.exe using a Linux ninja binary: /path/to/linux/ninja
  • Run: ./ninja.exe (implicitly runs through wine(!))