RFR: 8340923: The class LogSelection copies uninitialized memory [v3]

[Johan Sjölen]

On Wed, 25 Sep 2024 16:55:10 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

>> The class LogSelection's custom constructor does not initialize the whole _tags array but is lacking a custom copy constructor and assignment operator. This means that any copy will copy uninitialized memory, which is undefined behavior. UBSAN has seen this happen, as reported by Matthias Baesken.
>> 
>> For some surrounding context: Unified Logging uses a statically defined array size (`LogTag::MaxTag`) but uses the `LogTag::__NO_TAG` to signify the end of the array. Think "NULL-terminated string but log tags".
>> 
>> We fill the whole array to avoid this issue. Specifically, we filll the remainder of the array with `LogTag::__NO_TAG`.
>
> Johan Sjölen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Simplify

The failing GHA is unrelated to these changes. Thank you for the quick reviews and help.

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PR Comment: https://git.openjdk.org/jdk/pull/21185#issuecomment-2376333497