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docs/ninja_build.md

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+
+Ninja is a build system written with the specific goal of improving the edit-compile cycle time. It is used by default everywhere except when building for iOS.
+
+Ninja behaves very similar to Make -- the major feature is that it starts building files nearly instantly.  (It has a number of minor user interface improvements to make as well.)
+
+Read more about Ninja at [the Ninja home page](http://martine.github.com/ninja/).
+
+## Using it
+
+### Configure your system to use Ninja
+
+#### Install
+
+Ninja is included in depot\_tools as well as gyp, so there's nothing to install.
+
+## Build instructions
+
+To build Chrome:
+```
+cd /path/to/chrome/src
+ninja -C out/Debug chrome
+```
+
+Specify `out/Release` for a release build. I recommend setting up an alias so that you don't need to type out that build directory path.
+
+If you want to build all targets, use `ninja -C out/Debug all`. It's faster to build only the target you're working on, like 'chrome' or 'unit\_tests'.
+
+## Android
+
+Identical to Linux, just make sure `OS=android` is in your `GYP_DEFINES`. You want to build one of the _apk targets, e.g. `content_shell_apk`._
+
+## Windows
+
+Similar to Linux. It uses MSVS's `cl.exe`, `link.exe`, etc. so you still need to have VS installed. To use it, open `cmd.exe`, go to your chrome checkout, and run:
+```
+set GYP_DEFINES=component=shared_library
+python build\gyp_chromium
+ninja -C out\Debug chrome.exe
+```
+
+`component=shared_library` optional but recommended for faster links.
+
+You can also set `GYP_GENERATORS=ninja,msvs-ninja` to get both VS projects generated if you want to use VS just to browse/edit (but then gyp takes twice as long to run).
+
+If you're using Express or the Windows SDK by itself (rather than using a Visual Studio install), you'll need to run from a vcvarsall command prompt.
+
+### Debugging
+
+Miss VS for debugging?
+```
+devenv.com /debugexe chrome.exe --my-great-args "go here" --single-process etc
+```
+
+Miss Xcode for debugging? Read http://dev.chromium.org/developers/debugging-on-os-x/building-with-ninja-debugging-with-xcode
+
+### Without Visual Studio
+
+That is, building with just the WinDDK. This is documented in the [regular build instructions](http://dev.chromium.org/developers/how-tos/build-instructions-windows#TOC-Setting-up-the-environment-for-building-with-Visual-C-2010-Express-or-Windows-7.1-SDK).
+
+## Tweaks
+
+### Building through errors
+Pass a flag like `-k3` to make Ninja build until it hits three errors instead of stopping at the first.
+
+### Parallelism
+Pass a flag like `-j8` to use 8 parallel processes, or `-j1` to compile just one at a time (helpful if you're getting weird compiler errors).  By default Ninja tries to use all your processors.
+
+### More options
+There are more options. Run `ninja --help` to see them all.
+
+### Custom build configs
+
+You can write a specific build config to a specific output directory via the `-G` flags to gyp.  Here's an example from jamesr:
+`build/gyp_chromium -Gconfig=Release -Goutput_dir=out_profiling -Dprofiling=1 -Dlinux_fpic=0`
+
+## Bugs
+
+If you encounter any problems, please file a bug at http://crbug.com/new with label `ninja` and cc `thakis@` or `scottmg@`.  Assume that it is a bug in Ninja before you bother anyone about e.g. link problems.