RFR: 8349083: Factor out filename handling code from logging

[David Holmes]

On Mon, 3 Feb 2025 13:59:48 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

>> src/hotspot/share/utilities/filenameUtil.hpp line 41:
>> 
>>> 39:   // Expand wildcards in filename:
>>> 40:   // %p -> PID
>>> 41:   // %t -> timestamp in YY-MM-DD_HH_MM_SS format
>> 
>> Not just a "timestamp" though it is specifically the VM start time.
>
> The "timestamp" comes from `os::javaTimeMillis()`, it is not the VM start time. 
> 
> Unified logging captures the VM start time and uses it from its filename substitution.
> 
> 
>    output = new LogFileOutput(name, _vm_start_time);

Sorry then I have misunderstood the refactoring of this. I was expecting "%t" to always mean the VM start time - otherwise what time is it?

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PR Review Comment: https://git.openjdk.org/jdk/pull/23410#discussion_r1940918335