RFR: 8325002: Exceptions::fthrow needs to ensure it truncates to a valid utf8 string [v4]

[Thomas Stuefe]

On Tue, 30 Jul 2024 04:12:11 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Exceptions::fthrow uses a 1024 byte buffer to format the incoming exception message string, but this may not be large enough, leading to truncation. However, we should ensure we truncate to a valid UTF8 sequence.
>> 
>> The process is explained in the code. Thanks to @RogerRiggs and @djelinski for their suggestions on how to tackle this.
>> 
>> Testing:
>>  - new gtest exercises the truncation code with the different possibilities for bad truncation
>>  - tiers 1-3 sanity testing
>> 
>> Thanks.
>
> David Holmes has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix logic to allow for the buffer being partially filled.

ok

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Marked as reviewed by stuefe (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/20345#pullrequestreview-2206655823