Add GYP to GN conversion cookbook
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@@ -0,0 +1,684 @@ +# GYP->GN Conversion Cookbook + +[TOC] + +## Targets + +| *GYP* | *GN* | +|:-------------------------------------------------|:---------------------------------------------------| +| `'type': 'static_library', 'name': 'foo',` | `static_library("foo") {` or `source_set("foo") {` | +| `'type': 'shared_library', 'name': 'foo',` | `shared_library("foo") {` | +| `'type': 'loadable_module', 'name': 'foo',` | `loadable_module("foo") {` | +| `'type': '<(component)', 'name': 'foo',` | `component("foo") {` | +| `'type': 'executable', 'name': 'foo',` | `executable("foo") {` | +| `'type': '<(gtest_target_type)', 'name': 'foo',` | `test("foo") {` | +| `'type': 'none', 'name': 'foo',` | `group("foo") {` | + +### Note on static libraries + +A source\_set is basically a transparent static\_library. The source files +are compiled with the given options but not linked into anything. +Targets that depend on a source set get the source set's object files +linked into it. This saves the overhead of creating a static library on +disk, avoids weird linker issues when a static library has no source +files, and you can link source sets into shared libraries and have +symbols exported from the shared library. + +The last issue is a cause of a lot of headaches in the GYP build. If you +annotate a symbol as exported (i.e. `BASE_EXPORT`) then you can't have +it in a file that goes into a static library because the function might +be [stripped out](http://blogs.msdn.com/b/oldnewthing/archive/2014/03/21/10509670.aspx) +if it's not called from within the static library. This +prevents composing components of static libraries and exporting their +symbols. A source set avoids this issue and `EXPORT` has the desired +meaning of "export from the component this gets linked into" with no +surprising dead code stripping behavior. + +A disadvantage of source sets is that if an object file is completely +unused, it will still be linked into the result, which is not the case +for static libraries. A few places in the build depend on this behavior +(deliberately or accidentally). In general, small libraries that we +expect to be entirely used, test helpers, etc. can be source sets. There +is slightly less risk of subtle issues if you keep static libraries +static libraries, however. + +### Actions + +GYP + +``` +{ + 'action_name': 'foo', + 'inputs': [ 'bar.py' ], + 'outputs': [ '<(SHARED_INTERMEDIATE_DIR)/bar.out' ], + 'action': ['python', 'bar.py', '--la_dee_da' ], +}, +``` + +Unlike GYP, where an action is a part of a target, GN actions are +separate targets that you then depend on via deps from other targets: + +``` +action("foo") { + script = "bar.py" + outputs = [ "$target_gen_dir/bar.out" ] + args = [ "--la_dee_da" ] +} + +executable("foo.exe") { + ... + deps = [ ":foo" ] # Depend on the action to make sure it runs. +} +``` + +Rules in GYP become `action_foreach` in GN which work like actions but +iterate over a set of sources. + +### Copies + +GYP + +``` +'copies': [ + { + 'destination': '<(PRODUCT_DIR)/', + 'files': [ + '../build/win/dbghelp_xp/dbghelp.dll', + ], + }, +], +``` + +Unlike GYP, where copies are part of a target, GN copies are +separate targets that you then depend on via deps from other targets: + +``` +copy("bar") { + sources = [ "../path/to/secret.dll" ] + outputs = [ "$root_out_dir/{{source_file_part}}" ] +} + +component("base") { + ... + deps = [ "bar" } # Depend on the copy to make sure it runs. +} +``` + +## Platform checking + +| *GYP* | *GN* | +|:-------------------------------------|:---------------------| +| `'conditions': [['OS=="win"', {` | `if (is_win) {` | +| `'conditions': [['OS=="linux"', {` | `if (is_linux) {` | +| `'conditions': [['OS=="android"', {` | `if (is_android) {` | +| `'conditions': [['OS=="mac"', {` | `if (is_mac) {` | +| `'conditions': [['OS=="ios"', {` | `if (is_ios) {` | +| `'conditions': [['chromeos==1', {` | `if (is_chromeos) {` | + +## Typical sources and deps modifications + +### GYP + +``` +'sources': [ + 'a.cc', + 'b.cc', + 'c.cc', +], +'dependencies': [ + '<(DEPTH)/base/base.gyp:foo', +], +'conditions': [ + ['OS=="win"': { + 'sources!': [ + 'a.cc', + ], + 'sources': [ + 'foo.cc', + ], + 'dependencies': [ + '<(DEPTH)/base/base.gyp:bar', + ], + }, { + 'sources/': [ + ['exclude', '^b\\.cc$'], + ], + }], +], +``` + +### GN + +``` +sources = [ + "c.cc", +] +deps = [ + "//base:foo", +] + +if (is_win) { + sources += [ + "b.cc", + "foo.cc', + ] + deps += [ "//base:bar" ] +} else { + sources += [ "a.cc" ] +} +``` + +Note that in GN we prefer to only add files when needed, and don't add all of +them at first only to remove them later like in gyp. + +## Variable mappings + +### Build configuration + +Build configuration and feature flags are usually global in GYP. In GN +we try to limit global variables and instead put variables used by only +some files into `.gni` files. These files are then imported into your +buildfile by specifying at the top: + +``` +import("//build/config/features.gni") + +# ... now you can use the variables declared in features.gni. +if (is_tsan) { + # ... +} +if (cld_version == 2) { + # ... +} +``` + +Other flags only apply to one `BUILD.gn` file and those flags are +declared directly in that file (so other files can't use them). These +places are noted in the table below. + +| *GYP* | *GN* | *GN import* | +|:------------------------------------------------|:-------------------------------------------|:-----------------------------------------------| +| `arm_float_abi` | `arm_float_abi` | `//build/config/arm.gni` | +| `arm_neon` (0/1) | `arm_use_neon` (true/false) | `//build/config/arm.gni` | +| `arm_neon_optional` (0/1) | `arm_optionally_use_neon` (true/false) | `//build/config/arm.gni` | +| `arm_version` | `arm_version` | `//build/config/arm.gni` | +| `asan` (0/1) | `is_asan` (true/false) | `//build/config/sanitizers/sanitizers.gni` | +| `branding` ("Chromium"/"Chrome") | `is_chrome_branded` (true/false) | `//build/config/chrome_build.gni` | +| `build_for_tool=="drmemory"` | `enable_iterator_debugging=false` | (internal to `//build/config/BUILD.gn`) | +| `build_for_tool=="tsan"` | `enable_iterator_debugging=false` | (internal to `//build/config/BUILD.gn`) | +| `buildtype` ("Official"/"Dev") | `is_official_build` (true/false) | `//build/config/chrome_build.gni` | +| `chrome_multiple_dll` (0/1) | `is_multi_dll_chrome` (true/false) | `//build/config/chrome_build.gni` | +| `clang` (0/1) | `is_clang` (true/false) | (global) | +| `clang_use_chrome_plugins` (0/1) | `clang_use_chrome_plugins` (true/false) | (internal to `//build/config/clang/BUILD.gn`) | +| `component` ("shared_library"/"static_library") | `is_component_build` (true/false) | (global) | +| `desktop_linux` (0/1) | `is_desktop_linux` (true/false) | (global) | +| `disable_glibcxx_debug` (0/1) | `enable_iterator_debugging` (true/false) | (internal to `//build/config/BUILD.gn`) | +| `fastbuild` (0/1/2) | `symbol_level` (2/1/0 — values inverted) | `//build/config/compiler/compiler.gni` | +| `gomadir` | `goma_dir` | `//build/toolchain/goma.gni` | +| `ios_deployment_target` (string) | `ios_deployment_target` | `//build/config/ios/ios_sdk.gni` | +| `GYP_MSVS_OVERRIDE_PATH` environment variable | `visual_studio_path` | `//build/config/win/visual_studio_version.gni` | +| `GYP_MSVS_VERSION` environment variable | (none) | | +| `ios_sdk_path` | `ios_sdk_path` and `use_ios_simulator` | `//build/config/ios/ios_sdk.gni` | +| `lsan` (0/1) | `is_lsan` (true/false) | `//build/config/sanitizers/sanitizers.gni` | +| `mac_sdk_min` | `mac_sdk_min` | `//build/config/mac/mac_sdk.gni` | +| `mac_sdk_path` | `mac_sdk_path` | `//build/config/mac/mac_sdk.gni` | +| `mac_sdk` | `mac_sdk_version` | `//build/config/mac/mac_sdk.gni` | +| `mac_strip_release` | `enable_stripping` | `//build/config/mac/symbols.gni` | +| `mac_want_real_dsym` | `enable_dsyms` | `//build/config/mac/symbols.gni` | +| `msan` (0/1) | `is_msan` (true/false) | `//build/config/sanitizers/sanitizers.gni` | +| `SDKROOT` (Mac) | `sysroot` | `//build/config/sysroot.gni` | +| `sysroot` | `sysroot` | `//build/config/sysroot.gni` | +| `target_arch` ("ia32"/"x64"/"arm"/"mipsel") | `target_cpu` ("x86"/"x64"/"arm"/"mipsel") | (global) | +| `toolkit_views` (0/1) | `toolkit_views` | `//build/config/ui.gni` | +| `tsan` (0/1) | `is_tsan` (true/false) | `//build/config/sanitizers/sanitizers.gni` | +| `windows_sdk_path` | `windows_sdk_path` | (internal to `//build/config/win/BUILD.gn`) | + +### Feature flags + +| *GYP* | *GN* | *GN import* | +|:----------------------------------------|:-----------------------------------------------|:------------------------------| +| `cld_version` (number) | `cld_version` (number) | `//build/config/features.gni` | +| `configuration_policy` (0/1) | `enable_configuration_policy` (true/false) | `//build/config/features.gni` | +| `debug_devtools` (0/1) | `debug_devtools` (true/false) | `//build/config/features.gni` | +| `disable_ftp_support` (0/1) | `disable_ftp_support` (true/false) | `//build/config/features.gni` | +| `disable_nacl` (0/1) | `enable_nacl` (true/false) | `//build/config/features.gni` | +| `enable_app_list` (0/1) | `enable_app_list` (true/false) | `//build/config/features.gni` | +| `enable_autofill_dialog` (0/1) | `enable_autofill_dialog` (true/false) | `//build/config/features.gni` | +| `enable_background` (0/1) | `enable_background` (true/false) | `//build/config/features.gni` | +| `enable_captive_portal_detection` (0/1) | `enable_captive_portal_detection` (true/false) | `//build/config/features.gni` | +| `enable_chromevox_next` (0/1) | `enable_chromevox_next` (true/false) | `//build/config/features.gni` | +| `enable_extensions` (0/1) | `enable_extensions` (true/false) | `//build/config/features.gni` | +| `enable_google_now` (0/1) | `enable_google_now` (true/false) | `//build/config/features.gni` | +| `enable_hidpi` (0/1) | `enable_hidpi` (true/false) | `//ui/base/ui_features.gni` | +| `enable_managed_users` (0/1) | `enable_managed_users` (true/false) | `//build/config/features.gni` | +| `enable_mdns` (0/1) | `enable_mdns` (true/false) | `//build/config/features.gni` | +| `enable_one_click_signin` (0/1) | `enable_one_click_signin` (true/false) | `//chrome/common/features.gni` | +| `enable_pepper_cdms` (0/1) | `enable_pepper_cdms` (true/false) | `//build/config/features.gni` | +| `enable_plugins` (0/1) | `enable_plugins` (true/false) | `//build/config/features.gni` | +| `enable_plugin_installation` (0/1) | `enable_plugin_installation` (true/false) | `//build/config/features.gni` | +| `enable_basic_printing` (0/1) | `enable_basic_printing` (true/false) | `//build/config/features.gni` | +| `enable_print_preview` (0/1) | `enable_print_preview` (true/false) | `//build/config/features.gni` | +| `enable_rlz` (0/1) | `enable_rlz` (true/false) | `//build/config/features.gni` | +| `enable_spellcheck` (0/1) | `enable_spellcheck` (true/false) | `//build/config/features.gni` | +| `enable_session_service` (0/1) | `enable_session_service` (true/false) | `//build/config/features.gni` | +| `enable_task_manager` (0/1) | `enable_task_manager` (true/false) | `//build/config/features.gni` | +| `enable_themes` (0/1) | `enable_themes` (true/false) | `//build/config/features.gni` | +| `enable_webrtc` (0/1) | `enable_webrtc` (true/false) | `//build/config/features.gni` | +| `image_loader_extension` (0/1) | `enable_image_loader_extension` (true/false) | `//build/config/features.gni` | +| `input_speech` (0/1) | `enable_speech_input` (true/false) | `//build/config/features.gni` | +| `notifications` (0/1) | `enable_notifications` (true/false) | `//build/config/features.gni` | +| `ozone_platform_dri` (0/1) | `ozone_platform_dri` (true/false) | `//build/config/ui.gni` | +| `remoting` (0/1) | `enable_remoting` (true/false) | `//build/config/features.gni` | +| `safe_browsing` (0/1/2) | `safe_browsing_mode` (0/1/2) | `//build/config/features.gni` | +| `use_allocator` (`'none'`|`'tcmalloc'`) | `use_allocator` (`"none"`|`"tcmalloc"`) | (See "Allocator" below) | +| `ui_compositor_image_transport` (0/1) | `ui_compositor_image_transport` (true/false) | `//build/config/ui.gni` | +| `use_ash` (0/1) | `use_ash` (true/false) | `//build/config/ui.gni` | +| `use_athena` (0/1) | `use_athena` (true/false) | `//build/config/ui.gni` | +| `use_aura` (0/1) | `use_aura` (true/false) | `//build/config/ui.gni` | +| `use_brlapi` (0/1) | `use_brlapi` (true/false) | `//build/config/features.gni` | +| `use_cairo` (0/1) | `use_cairo` (true/false) | `//build/config/ui.gni` | +| `use_clipboard_aurax11` (0/1) | `use_aura && use_x11` | | +| `use_cups` (0/1) | `use_cups` (true/false) | `//build/config/features.gni` | +| `use_dbus` (0/1) | `use_dbus` (true/false) | `//build/config/features.gni` | +| `use_gconf` (0/1) | `use_gconf` (true/false) | `//build/config/features.gni` | +| `use_glib` (0/1) | `is_linux` (true/false) | (global) | +| `use_gnome_keyring` (0/1) | `use_gnome_keyring` (true/false) | | +| `use_goma` (0/1) | `use_goma` (true/false) | `//build/toolchain/goma.gni` | +| `use_nss_certs` (0/1) | `use_nss_certs` (true/false) | `//build/config/crypto.gni` (Many of these conditions can be deleted, see the "SSL" notes on targets below.) | +| `use_pango` (0/1) | `use_pango` (true/false) | `//build/config/ui.gni` | +| `use_ozone` (0/1) | `use_ozone` (true/false) | `//build/config/ui.gni` | +| `use_seccomp_bpf` (0/1) | `use_seccomp_bpf` (true/false) | `//build/config/features.gni` | +| `use_udev` (0/1) | `use_udev` (true/false) | `//build/config/features.gni` | +| `use_x11` (0/1) | `use_x11` (true/false) | `//build/config/ui.gni` | +| `use_xi2_mt` (0/1) | `use_xi2_mt` (true/false) | `//build/config/ui.gni` | +| `win_use_allocator_shim` (0/1) | | (See "Allocator" below) | + +### Common target conversion + +Some targets that lots of projects depend on and how the GN ones +correspond to GYP ones. (This is for commonly-depended-on or weird +targets only, don't add stuff here just because you converted it.) + +| *GYP* | *GN* | *Notes* (see below) | +|:-----------------------------------------------------------------------------------|:-----------------------------------------|:---------------------| +| `base/base.gyp:base` | `//base` | | +| `base/base.gyp:base_i18n` | `//base:i18n` | | +| `base/base.gyp:run_all_unittests` | `//base/test:run_all_unittests` | | +| `base/base.gyp:test_support_base` | `//base/test:test_support` | | +| `base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations` | `//base/third_party/dynamic_annotations` | | +| `build/linux/system.gyp:*` (except nss) | `//build/config/linux:*` | Linux system targets | +| `build/linux/system.gyp:nss` | `//crypto:platform` | SSL | +| `net/third_party/nss/ssl.gyp:libssl` | `//crypto:platform` | SSL | +| `skia/skia.gyp:skia` | `//skia` | | +| `testing/gmock.gyp:gmock` | `//testing/gmock` | Secondary tree | +| `testing/gtest.gyp:gtest` | `//testing/gtest` | Secondary treeo | +| `third_party/icu/icu.gyp:icui18n` | `//third_party/icu` | Secondary tree, ICU | +| `third_party/icu/icu.gyp:icuuc` | `//third_party/icu` | Secondary tree, ICU | +| `url/url.gyp:url_lib` | `//url` || || + +Notes: + + * *ICU:* GN has separate `//third_party/icu:icuuc` and + `//third_party/icu:icui18n` targets just like GYP. You can use these + if you only need one of them. Most targets want both, so GN made a + meta target that's just `//third_party/icu` which you can use that + redirects to both "uc" and "i18n". + + * *Linux system targets:* Generally the names in GN patch the GYP + names for the Linux system-related stuff. However, most of them are + configs instead of actual targets (in GYP they're all targets). For + example, since "x11" is just a list of libraries and include + directories, and includes no sources it's a config that just adds + this configuration to your target. To use a config, do `configs += [ + "//build/config/linux:x11" ]` + + * *Secondary tree:* Some projects are DEPSed in and we want it to look + like a BUILD.gn file is in that directory without checking it in to + the upstream repo. The directory `build/secondary` mirrors the main + tree and is checked for BUILD.gn files if an expected file in the + main tree wasn't found. + + * *SSL:* In GYP there are lots of conditions around NSS vs. OpenSSL + and different platforms that determine which of the different SSL + libraries is linked. In GN, there is a meta-target + `//crypto:platform` that will "do the right thing" according to the + current build platform and flags. Generally its safe to replace any + conditional reference to a SSL library with this one. + +## Visibility and header file issues + +GN is much more strict about header file checking. You may encounter +errors that your target doesn't depend on the target containing a +certain header file. The most common example is including +`base/macros.h` without having `//base` in your project's dependency +list. The solution is to just add the missing dependency. + +The dependency tree must be a DAG. Some components might share headers +between a number of internal targets that makes adding the "proper" +dependencies impossible. In this case, you can separate out a +`source_set` type target containing just the header(s) in question, and +make the targets that use that header depend on that source set to break +the cycle. + +## Other stuff + +### Target conditions + +`target_conditions` are like normal conditions but expanded in a +different phase of GYP. You can generally just convert the conditions +inside and not worry about the `conditions`/`target_conditions` +difference. + +### xcode_settings + +Some xcode settings are obvious: + +``` + 'xcode_settings': {'OTHER_LDFLAGS': ['-foo']}, +``` + +Should just expand to: + +``` + ldflags = [ "-foo" ] +``` + +Other flags are less obvious: + +``` + 'xcode_settings': { 'GCC_SYMBOLS_PRIVATE_EXTERN': 'NO', }, +``` + +These all correspond to various flags that get passed to the compiler or +linker. You can use your favorite search engine to see what it +corresponds to, but many of them are not well documented. You can also +search for the string in +[tools/gyp/pylib/gyp/xcode_emulation.py](https://code.google.com/p/chromium/codesearch#chromium/src/tools/gyp/pylib/gyp/xcode_emulation.py). GYP uses this file to decode +the Xcode settings into command line flags for the ninja build. + +### wexit-time destructors + +Replace + +``` +'enable_wexit_time_destructors': 1, +``` + +with + +``` +configs += [ "//build/config/compiler:wexit_time_destructors" ] +``` + +### Chromium code + +In GYP code is "non-Chromium" by default, and you opt into higher warning levels using: + +``` +'chromium_code': 1, +``` + +In GN, all code is Chromium code by default. If you're compiling a +static library that needs more lax warnings, opt out of the +Chromium-code settings with: + +``` +configs -= [ "//build/config/compiler:chromium_code" ] +configs += [ "//build/config/compiler:no_chromium_code" ] +``` + +### -fvisibility + +All symbols in the build have "hidden" visibility by default (this means +that symbols aren't exported from shared libraries, a concept different +than GN's target visibility). If you needed to export all symbols (for a +third party library) by default in GYP you would do: + +``` +'xcode_settings': [ + 'GCC_SYMBOLS_PRIVATE_EXTERN': 'NO', # no -fvisibility=hidden +], +'cflags!': [ + '-fvisibility=hidden', +], +``` + +In GN the equivalent is: + +``` +if (!is_win) { + configs -= [ "//build/config/gcc:symbol_visibility_hidden" ] +} +``` + +### Dependent settings + +In GYP you'll see stuff like this, especially in third-party code. + +``` +'direct_dependent_settings': { + 'include_dirs': [ + '.', # This directory. + '../..', # Root "src" path. + ], + 'defines': [ + 'FOO', + ], +}, +``` + +Note that many of the includes are trying to add the root "src" +directory to the include path. This is always present in GN so you can +remove these. + +GYP also requires you to duplicate these settings, once for the target +itself, and once for the direct/all dependent settings. In GN, +public/all dependent configs also apply to the current target so you +only need to specify it once. + +In GN, put the settings in a config (declared above your target), and +then reference that as a public config in your target: + +``` +config("foo_config") { + include_dirs = [ "." ] + defines = [ "FOO" ] +} + +component("foo") { + ... + public_configs = [ ":foo_config" ] +} +``` + +Targets that depend on `foo` will now get `foo_config` applied. + +GYP would say `export_dependent_settings` to forward +`direct_dependent_settings` up the dependency chain. In GN, put the +dependency in the `public_deps` section and this will happen +automatically. + +### MSVS disabled warnings + +In GYP you'll see for third-party code: + +``` +'msvs_disabled_warnings': [ 4018, 4244, 4267, ], +``` + +At least half of the warnings in these blocks are already disabled +globally (we added more global ones later). From the command line, do: + +``` +$ cd src/build/config +$ git grep 4018 +compiler/BUILD.gn: "/wd4018", # Comparing signed and unsigned values. +``` + +tells us that warning 4018 is already disabled globally from the +`default_warning_flags` variable in `//build/config/compiler`, and the same +for 4244. So ignore these. + +Always comment what the warning is. Use your favorite search engine and +type "vc warning 4267" to look it up. You'll end up with: + +``` +if (is_win) { + cflags += [ + "/wd4267", # Conversion from size_t to 'type'. + ] +} +``` + +(Use `=` instead of `+=` is you haven't already defined a `cflags` variable.) + +### Mac frameworks + +GN knows to convert `.framework` files in the `libs` list to the right +thing on Mac. You don't need to specify the directories either. So +convert this: + +``` +'link_settings': { + 'libraries': [ + '$(SDKROOT)/System/Library/Frameworks/Accelerate.framework', + ], +}, +``` + +to this: + +``` +libs = [ "Accelerate.framework" ] +``` + +### hard_dependency + +GYP code sometimes sets + +``` + 'hard_dependency': 1, +``` + +to indicate that the current target must be build before its dependents. +GN can deduce this internally, so you can ignore this directive. + +### Allocator + +GYP has `win_use_allocator_shim` and `use_allocator`. In GN, these are +merged into `use_allocator` which is defined in +`//build/config/allocator.gni`. _However_ you should almost never need +to use this flag. The `//base/allocator` target will change depending on +the current allocator flag, so you can unconditionally depend on this +target to pick up the current build defaults. + +This: + +``` + ['use_allocator!='none'', { + 'dependencies': [ '../base/allocator/allocator.gyp:allocator' ] + }], + ['win_use_allocator_shim==1', { + 'dependencies': [ '<(allocator_target)' ], + }], +``` + +Becomes: + +``` + deps = [ "//base/allocator" ] +``` + +As in GYP, the allocator should only be depended on by executables (and +tests). Libraries should not set the allocator. + +### optimize: max + +In Gyp: + +``` +'optimize': 'max', +``` + +only affects Windows and will optimize for speed rather than size. To +get the same behavior in GN, do: + +``` +if (!is_debug && is_win) { + configs -= [ "//build/config/compiler:default_optimization" ] + configs += [ "//build/config/compiler:optimize_max" ] +} +``` + +The `is_win` check is needed because the `optimize_max` config also +affects Posix systems. Some components might additionally specify `-O2` +on Posix further optimize, in which case you can remove the `is_win` +check. + +### Protobufs + +``` +import("//third_party/protobuf/proto_library.gni") + +proto_library("myproto") { + sources = [ "foo.proto" ] +} +``` + +See the `third_party/protobuf/proto_library.gni` file for full +documentation and extra flags. + +### Java stuff + +JNI generator in GYP: + +``` +{ + 'target_name': 'foo_headers', + 'type': 'none', + 'sources': [ <java files> ] + 'variables': { 'jni_gen_package': 'foobar' } + 'includes': [ 'build/jni_generator.gypi' ] +} +``` + +JNI generator in GN: + +``` +# At top of file: +if (is_android) { + import("//build/config/android/rules.gni") +} + +# Later: +if (is_android) { + generate_jni("foo_headers") { + sources = [ <java files> ] + jni_package = "foobar" + } +} +``` + +### Grit + +``` +import("//tools/grit/grit_rule.gni") + +grit("resources") { + source = "my_resources.grd" +} +``` + +See `src/build/secondary/tools/grit/grit_rule.gni` for more documentation. + +### Mojo + +``` +import("//mojo/public/tools/bindings/mojom.gni") + +mojom("mojo_bindings") { + sources = [ + "foo.mojom", + ] +} +```