Option --starlark_cpu_profile is completely broken on Windows

[konste]

Description of the problem / feature request:

--starlark_cpu_profile command-line option crashes Bazel server on Windows.

Bugs: what's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

For absolutely any Bazel build on Windows adding --starlark_cpu_profile=pprof.gz to the command line causes immediate server failure: Server terminated abruptly (error code: 2, error message: 'Stream removed', log file: 'c:\_\jjgeprbx\server\jvm.out')
jvm.out file mentioned is absolutely empty.
I have verified the problem is present on multiple Windows machines, but does not reproduce on Mac and Linux.

What operating system are you running Bazel on?

Windows 10 20H2

What's the output of bazel info release?

4.1.0, 4.2.0rc1

[konste]

@meteorcloudy could you please take a peek as the Windows expert? It is trivial to repro and broken completely, so I hope it may be a small fix.

[meteorcloudy]

Thanks for the report! I'll look into it.
/cc @meisterT

[andrewkatson]

I got a stack trace

FATAL: bazel crashed due to an internal error. Printing stack trace:
java.lang.UnsupportedOperationException: this platform does not support Starlark profiling
	at net.starlark.java.eval.CpuProfiler.start(CpuProfiler.java:131)
	at net.starlark.java.eval.Starlark.startCpuProfile(Starlark.java:963)
	at com.google.devtools.build.lib.runtime.BlazeCommandDispatcher.execExclusively(BlazeCommandDispatcher.java:367)
	at com.google.devtools.build.lib.runtime.BlazeCommandDispatcher.exec(BlazeCommandDispatcher.java:231)
	at com.google.devtools.build.lib.server.GrpcServerImpl.executeCommand(GrpcServerImpl.java:547)
	at com.google.devtools.build.lib.server.GrpcServerImpl.lambda$run$1(GrpcServerImpl.java:611)
	at io.grpc.Context$1.run(Context.java:579)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.base/java.lang.Thread.run(Unknown Source)

This shouldn't be too bad I'll start working on a solution.

[meteorcloudy]

Looks like this isn't a bug, but a feature request since the cpu profiler is not yet implemented on Windows.
https://cs.opensource.google/bazel/bazel/+/master:src/main/java/net/starlark/java/eval/BUILD;l=95;bpv=0

[meteorcloudy]

/cc @brandjon

[meisterT]

I guess it still shouldn't crash hard

[meteorcloudy]

IIUC, Andrew is looking into porting cpu_profiler_posix.cc to Windows. If that doesn't work, we'll make it fail gracefully.

[konste]

@andrewkatson could you please comment for me how you got that stack trace?

[andrewkatson]

It was actually in jvm.out!

[konste]

Weird! For me jvm.out was completely empty.

[andrewkatson]

Still working on this! Should have something to test out soon.

[andrewkatson]

Havent gotten the chance to look at this for a bit. Hoping I can do something soon

[andrewkatson]

Okay I've got a solution. I went with just ignoring and logging that the option is unsupported. The windows api lacks key functionality in order to get this information

[konste]

O-oh-h... that's too bad. Even partial functionality cannot be achieved on Windows? What exactly the missing API should do?

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[github-actions]

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