On Tue, 13 Jan 2026 16:52:36 GMT, Ioi Lam <[email protected]> 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.
> 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 after 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. > > ### Progress > * [ ] Change must be properly reviewed (1 review required, with at least 1 > [Reviewer](https://openjdk.org/bylaws#reviewer)) > * [x] Change must not contain extraneous whitespace > * [x] Commit message must refer to an issue > > ### Issue > * [JDK-8366736](https://bugs.openjdk.org/browse/JDK-8366736): Closed > System.out causes child process to hang on Windows (**Bug** - P4) > > ### Reviewing > Using `git` > Checkout this PR locally: `$ git fetch https://git.openjdk.org/jdk.git > pull/29198/head:pull/29198` `$ git checkout pull/29198` > > Update a local copy of the PR: `$ git checkout pull/29198` `$ git pull > https://git.openjdk.org/jdk.git pull/29198/head` > > Using Skara CLI tools > Checkout this PR locally: `$ git pr checkout 29198` > > View PR using the GUI difftool: `$ git pr show -t 29198` > > Using diff file ------------- PR Comment: https://git.openjdk.org/jdk/pull/29198#issuecomment-3745764159
