Enable batchfiles to run via CreateProcessW

[ahewitson-ops]

Description

Enables Batchfiles to be ran via CreateProcessW even when their paths exceed MAX_PATH when running in tw.exe.

Looks to fix #30431

Motivation

#29921 helped us Windows users by enabling long paths for all .exe files, but specifically left out Batch/cmd files. Specifically because .bat and .cmd files must be run through an interpreter like cmd.exe, as stated in the CreateProcessW documentation.

However, testing shows that CreateProcessW can in fact handle being given a .bat or .cmd file above long paths, and silently rewrites the call to shunt it over to cmd.exe without the user having to do anything. The only caveat is that cmd.exe does not understand the \\?\ prefix for long paths and so a .bat/.cmd path must be passed without it.

I want to also note the manifest changes came from @nwatkiss in another PR for handling long paths HERE.

Note that this only works in places where a longpathAware manifest is applied to the binary.

Build API Changes

No

Checklist

• I have added tests for the new use cases (if any).
• I have updated the documentation (if applicable).

Release Notes

RELNOTES: Allows Batchfiles ran by CreateProcessW in tw.exe to work under longpathAware.

[ahewitson-ops]

As Marc pointed out in the Windows channel, in theory this could be working but slow because windows first tries to run it as a PE binary and then silently rewrites to cmd.exe when that fails.

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Updated for 8b84a81f294f2df6bf1c34ea090146277ad9be45

[meteorcloudy]

Enable Batchfiles to also be ran when their paths exceed MAX_PATH.

Do I understand correctly this only works under tw.exe because we have enabled longpathAware in the mainifest file? For example, this wouldn't work in process_test.exe or bazel.exe since they don't have longpathAware enabled.

[fmeum]

What matters for Bazel is the manifest of the embedded java.exe, which we already patch extensively. We could make it long path aware too, but we would need to check whether the JDK has issues with that.

[meteorcloudy]

I'm fine with fixing tw.exe only, but we should be clear in the PR description about what are the actual conditions for this to work

[ahewitson-ops]

Enable Batchfiles to also be ran when their paths exceed MAX_PATH.

Do I understand correctly this only works under tw.exe because we have enabled longpathAware in the mainifest file? For example, this wouldn't work in process_test.exe or bazel.exe since they don't have longpathAware enabled.

Using long paths in general? Yes, it's only because we have a manifest file for tw.exe that enables longpathAware so any executable without that cannot use long paths. If we wanted to make process_test or bazel longpath aware then yeah we'd have to make sure they have a manifest as well.

I've updated the PR description a little and the release notes.

[meteorcloudy]

I believe the host Windows machine also has to enable LongPathsEnabled = 1 in the Windows registry?

[ahewitson-ops]

I believe the host Windows machine also has to enable LongPathsEnabled = 1 in the Windows registry?

Yes, which I believe is the default nowadays for Windows machines. But this PR doesn't really change the need for that registry key, as it was already added in #29921

[meteorcloudy]

nit: should we also update comment here?

[meteorcloudy]

Should this be:

ASSERT_TRUE(proc.Create(bat_path, L"", nullptr, L".", devnull, pipe_write,
                        stderr_dup, nullptr, &proc_error))
    << blaze_util::WstringToCstring(proc_error);

?

[meteorcloudy]

Thanks!