RFR: 8291023: FileOutputStream.close() re-entrantly invokes itself via FileChannel.close()

[Archie L. Cobbs]

On Thu, 6 Apr 2023 22:36:33 GMT, Archie L. Cobbs <duke at openjdk.org> wrote:

> IO stream classes like `FileOutputStream` can have assocated NIO channels.
> 
> When `close()` is invoked on one of these classes, it in turn invokes `close()` on the associated channel (if any). But when the associated channel's `close()` method is invoked, it in turn invokes `close()` on the associated stream (if any).
> 
> As a result, these IO stream `close()` methods invoke themselves reentrantly when there is an associated channel.
> 
> This is not a problem for these classes because they are written to handle this (i.e., they are idempotent), but it can be surprising (or worse, just silently bug-inducing) for subclasses that override `close()`.
> 
> There are two possible ways to address this:
> 1. Modify the code to detect and avoid the (unnecessary) reentrant invocations
> 2. Add a `@implNote` to the Javadoc so subclass implementers are made aware
> 
> This patch takes the second, more conservative approach.

Good suggestions - thanks. Implemented in 9978b52ed73.

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PR Comment: https://git.openjdk.org/jdk/pull/13379#issuecomment-1500326488