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

[David Holmes]

On Tue, 1 Dec 2020 12:04:43 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Harold Seigel has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   8256718: Obsolete the long term deprecated and aliased Trace flags
>
> 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.

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