RFR: 8366736: Closed System.out causes child process to hang on Windows [v7]

[Alan Bateman]

On Sun, 15 Feb 2026 06:01:02 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> The bug is here on line 121:
>> 
>> https://github.com/openjdk/jdk/blob/586846b84a38d285c5905437e903cfc57f609410/src/java.base/windows/classes/java/lang/ProcessImpl.java#L118-L121
>> 
>> If `System.out` has been closed, `fdAccess.getHandle()` will return -1. This causes `stdHandles[1]` to have the same value as if the child process's stdout was redirected with `Redirect.PIPE`. This will cause a Pipe to be created here for the child process's STDOUT on line 168:
>> 
>> https://github.com/openjdk/jdk/blob/586846b84a38d285c5905437e903cfc57f609410/src/java.base/windows/native/libjava/ProcessImpl_md.c#L158-L184
>> 
>> However, the caller of the `ProcessBuilder` is not aware of this and will not drain this pipe. This causes the child process to get stuck when writing to its stdout when the pipe 's buffer is filled up.
>> 
>> The fix is to treat the redirection as `Redirect.DISCARD` when `System.out` and/or `System.err` have been closed.
>
> Ioi Lam 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 11 additional commits since the last revision:
> 
>  - Review comment by @AlanBateman: use implNote instead. Also fixed whitespaces
>  - Merge branch 'master' into 8366736-closed-system-out-causes-child-process-to-hang-on-windows
>  - @RogerRiggs review comments
>  - Fixed typo
>  - fixed typo
>  - Merge branch 'master' into 8366736-closed-system-out-causes-child-process-to-hang-on-windows
>  - Review comments from @RogerRiggs
>  - Reverted previous unintended commit
>  - 8375654: Exclude all array classes from dynamic CDS archive
>  - Review comments from @RogerRiggs
>  - ... and 1 more: https://git.openjdk.org/jdk/compare/f3eaab4c...bc999867

src/java.base/share/classes/java/lang/ProcessBuilder.java line 935:

> 933:      * @implNote
> 934:      * When the process is {@link #start started},
> 935:      * if {#code System.out} and/or {#code System.err} have been

Thanks for moving it to an implNote. For word smithing, It might be better to say "and System.out and/or System.err has been closed". Also it would be better to say the current VM rather than the current process here as these APIs relate to the current VM.

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PR Review Comment: https://git.openjdk.org/jdk/pull/29198#discussion_r2815168712