RFR: 8256718: Obsolete the long term deprecated and aliased Trace flags [v2]

[Coleen Phillimore]

On Tue, 1 Dec 2020 23:01:51 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> src/hotspot/share/runtime/arguments.cpp line 612:
>> 
>>> 610:   { "TraceRedefineClasses",      "-Xlog:redefine+class=",      "info",  "16.0" },
>>> 611:   { "PrintJNIResolving",         "-Xlog:jni+resolve=",         "debug", "16.0" },
>>> 612:   { NULL, NULL, NULL, NULL }
>> 
>> I think if we wanted to give a message that the flag was obsolete and to suggest changing the command line, we should only do it for -XX:+TraceClassLoading and -XX:+TraceExceptions (I'd originally thought -XX:+TraceClassUnloading was important enough to release note but now I'm not so sure.)   The rest of the flags should either go in the table that they're no longer recognized.
>
> Keeping the message for any flag requires keeping all the supporting code. I don't see the "big 3" are special. They have been deprecated since 9 and we have clearly told people this when they use them. We're also release-noting this for 16 (again - this was documented when UL was added). I don't think we have to pander to anyone who hasn't updated their launch scripts by now.

For these three, I kind of like the pandering.  I'm not sure that the release note will reach people using these, especially -XX:+TraceExceptions.  I guess they've been getting a deprecation message since 9 so maybe it won't be such a surprise.  I never stand in the way of removing code that people won't need, if you think this is the case.

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PR: https://git.openjdk.java.net/jdk/pull/1525