RFR(s): 8143291: Remove redundant coding around os::exception_name

[Coleen Phillimore]

I am on US Thanksgiving holiday but this looks great.  I'm happy to see 
these cleanups.  It'll make working on the code better.

Can you remove the bogus

  //Reconciliation History


lines from jvm_solaris.cpp while you're here?

Are JVM_RaiseSignal and JVM_RegisterSignal on xnix platforms mostly 
duplicate now?  A further RFE?

Thanks,
Coleen

On 11/27/15 11:04 AM, Thomas Stüfe wrote:
> Ping...
>
> Could I have a second review please?
>
> The current webrev is:
> http://cr.openjdk.java.net/~stuefe/webrevs/8143291/webrev.03/webrev/
> And the bug report:    https://bugs.openjdk.java.net/browse/JDK-8143291
>
> Thank you!
>
> ..Thomas
>
>
> On Thu, Nov 19, 2015 at 11:23 AM, Thomas Stüfe <thomas.stuefe at gmail.com>
> wrote:
>
>> Hi,
>>
>> please take a look at this change.
>>
>> bug: https://bugs.openjdk.java.net/browse/JDK-8143291
>> webrev:
>> http://cr.openjdk.java.net/~stuefe/webrevs/8143291/webrev.00/webrev/
>>
>> This fix does some cleanups around os::exception_name().
>>
>> - os::exception_name() is identical on all Posix platforms (it returns a
>> signal name string for a signal number), so it can be merged into
>> os_posix.cpp
>>
>> - There is no need for a platform-specific implementation, as we have
>> already os::Posix::get_signal_name(). Use that instead of platform-specific
>> solutions.
>>
>> - I added a function os::Posix::get_signal_number() which is the inverse
>> of os::Posix::get_signal_name().
>>
>> - Before, a signal-to-number table was kept in jvm_<os>.cpp. That was used
>> to implement os::exception_name() and also for JVM_FindSignal
>> -> on AIX, I removed the coding altogether and used
>> os::Posix::get_signal_number() as a base for JVM_FindSignal.
>> -> on the other Unices, I did not feel so confident, because strictly
>> spoken we may change the behaviour slightly to before:
>> os::Posix::get_signal_name() knows more signal names than the platform
>> specific tables knew before, so now Signal.findSignal("<name>") would
>> return more matches than before.
>> I am not sure whether I am overcautious here - should I treat the other
>> Unices the same way I treated AIX, i.e. implement
>> Signal.findSignal("<name>") -> JVM_FindSignal via
>> os::Posix::get_signal_number()? This would further simplify the coding.
>>
>> Oh, this fix also fixes an issue where os::exception_name() would return
>> NULL for an unknown signal number, but no caller ever checks for NULL
>> before printing the result. The new os::exception_name() always returns a
>> string and also distinguishes between "unknown but valid signal" and
>> "invalid signal".
>>
>> Kind Regards, Thomas
>>
>>
>>