AOSP build debugging. Ninja output

Android AOSP build errors are usually very tricky to debug. AOSP build consists of dozens of makefiles not to mention Blueprint or Android.bp files introduced with Soong. Android put Soong Build System on top of existing makefiles starting from 7.0 release. For input it takes makefiles and .bp files from hundreds of repositories included in AOSP. On output it produces executables, images, build system intermediaries, etc.

When you got build failure at least the following AOSP build logs are available for examination (probably not comprehensive):

• out/soong.log
• out/verbose.log.gz/verbose.log

Ninja is on the lower level of build hierarchy. It starts final build commands generated on all previous steps. If build error is related to Ninja there is a bunch of convenient internal tools for investigation.

For example, I got the following error in out/soong.log

build/soong/ui/build/dumpvars.go:109: BOARD_SUPPORTS_EARLY_INIT true
build/soong/ui/build/exec.go:57: build/blueprint/bootstrap.bash [build/blueprint/bootstrap.bash -t]
build/soong/ui/build/exec.go:57: out/soong/.bootstrap/bin/soong_env [out/soong/.bootstrap/bin/soong_env out/soong/.soong.environment]
build/soong/ui/build/exec.go:57: prebuilts/build-tools/linux-x86/bin/ninja [prebuilts/build-tools/linux-x86/bin/ninja -d keepdepfile -w dupbuild=err -j 4 --frontend_file out/.ninja_fifo -f out/soong/.minibootstrap/build.ninja]
build/soong/ui/build/exec.go:57: prebuilts/build-tools/linux-x86/bin/ninja [prebuilts/build-tools/linux-x86/bin/ninja -d keepdepfile -w dupbuild=err -j 4 --frontend_file out/.ninja_fifo -f out/soong/.bootstrap/build.ninja]
build/soong/ui/build/exec.go:95: soong bootstrap failed with: exit status 2

I found a corresponding code in Soong source and passed additional parameters to Ninja.

file: build/soong/ui/build/soong.go at the end of func runSoong()

func runSoong(ctx Context, config Config) {

... 

ninja := func(name, file string) {

ctx.BeginTrace(metrics.RunSoong, name)

defer ctx.EndTrace()

fifo := filepath.Join(config.OutDir(), ".ninja_fifo")

nr := status.NewNinjaReader(ctx, ctx.Status.StartTool(), fifo)

defer nr.Close()

cmd := Command(ctx, config, "soong "+name,

config.PrebuiltBuildTool("ninja"),

"-d", "keepdepfile",

"-w", "dupbuild=err",

"-j", strconv.Itoa(config.Parallel()),

"--frontend_file", fifo,

"-f", filepath.Join(config.SoongOutDir(), file))

cmd.Sandbox = soongSandbox

cmd.RunAndPrintOrFatal()

}

ninja("minibootstrap", ".minibootstrap/build.ninja")

ninja("bootstrap", ".bootstrap/build.ninja")

} 

 

Notice 2 invocations of function ninja() that provides log entries for minibootstrap and bootstrap.