RFR: 8364361: [process] java.lang.Process should implement Closeable [v15]

[Alan Bateman]

On Wed, 8 Oct 2025 02:11:53 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

>> The teardown of a Process launched by `ProcessBuilder` includes the closing of streams and ensuring the termination of the process is the responsibility of the caller. The `Process.close()` method provides a clear and obvious way to ensure all the streams are closed and the process terminated.
>> 
>> The try-with-resources statement is frequently used to open streams and ensure they are closed on exiting the block. By implementing `AutoClosable.close()` the completeness of closing the streams and process termination can be done by try-with-resources.
>> 
>> The actions of the `close()` method are to close each stream and destroy the process if it has not terminated.
>
> Roger Riggs has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 22 additional commits since the last revision:
> 
>  - The ProcessCloseTest is modified to be able to test the logic
>    around close() waiting for the process to exit and the specified
>    behavior of interrupting the waitFor.
>  - Close is modified to wait for the process to terminate before returning.
>    Please review the revised javadoc.
>    As suggested in review comments, waiting for the process to terminate
>    allows a more orderly cleanup by the application.
>    The streams are closed and close uses `waitFor()` with an unlimited timeout
>    for the process to terminate.
>    While waiting the thread can be `interrupted` to exit the `waitFor`.
>    If/when `waitFor` is interrupted, the process is destroyedForcibly on
>    all platforms. When close() returns, the thread interrupt will pending
>    and can be handled by the caller.
>    If a watchdog timeout is desired on close(), a separate thread
>    can schedule an interrupt at a suitable time after close is called.
>  - Review comment improvements to make expected behavior clearer.
>  - Merge branch 'master' into 8364361-process-autocloseable
>  - Clarify the use of waitFor after close() or T-W-R exit.
>  - Additional review feedback.
>    Updated to emphasize reading the data from the streams and calling waitFor
>    to allow for normal termination.
>  - Merge branch 'master' into 8364361-process-autocloseable
>  - Address review comments for code and javadoc in Process, the test and the example.
>    Reinforced that calling waitFor should occur before calling close to wait for termination and get the exitStatus.
>    Corrected the error message check for invalid handles on Windows.
>    Update test to allow normal completion when exceptions may be expected.
>    Correct the expected message on Windows for an invalid handle exception.
>  - Update close() to use "terminate" consistently.
>  - Remove volatile from "closed" field; updates are guarded by synchronized.
>  - ... and 12 more: https://git.openjdk.org/jdk/compare/17e05424...6f8f7327

src/java.base/share/classes/java/lang/Process.java line 235:

> 233:                 destroyForcibly();
> 234:                 // Re-assert the interrupt
> 235:                 Thread.currentThread().interrupt();

I think this is still problematic as code after the t-w-r can't be guaranteed that the child has terminated. So I think it needs a loop that ends when waitFor completes without an exception (destroyForcibly would only be called on the first interrupt of course).

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PR Review Comment: https://git.openjdk.org/jdk/pull/26649#discussion_r2412541369