RFR: JDK-8288003: log events for os::dll_unload [v4]

[Yasumasa Suenaga]

On Fri, 10 Jun 2022 07:38:03 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

>> Currently we only log events for os::dll_load, but not for os::dll_unload, this patch adds it. On some platforms (Linux/Windows) we can use OS APIs (e.g. dlinfo on Linux) to log the path of the unloaded shared lib.
>
> Matthias Baesken has updated the pull request incrementally with one additional commit since the last revision:
> 
>   dll_path on Linux - add NULL check, change special output to not available

Why didn't you add NULL check to `os::dll_unload()` both os_windows and os_posix?
If NULL is passed to `os::dll_unload()` at os_windows.cpp, it would be passed to `GetModuleFileName()`, then we would get executable path.

I think we can add `assert` to the start of both `dll_load()` because NULL shouldn't be passed to them.

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PR: https://git.openjdk.org/jdk/pull/9101