RFR 8243572: Multiple tests fail with assert(cld->klasses() != 0LL) failed: unexpected NULL for cld->klasses()

[Lois Foltan]

Looks good.
Lois

On 4/28/2020 1:27 PM, Harold Seigel wrote:
> Hi,
>
> Please review this fix for JDK-8243572 and JDK-8243336.  Both failures 
> were caused by calling function ClassLoaderData::klasses() and 
> expecting a non-null return value. However, when the CLD had no 
> classes then NULL was returned causing the assertion failure in one 
> case and SIGSEGV in the other.
>
> Function klasses() was called in these places to determine if the 
> ClassLoaderData was for a hidden class or an unsafe anonymous class.  
> This was done during CLD statistics collection and for JFR events 
> involving CLD's.
>
> Since the JDK has replaced uses of unsafe anonymous classes with 
> hidden classes, there should be very few unsafe anonymous classes.  
> So, it was decided (with mgronlun and mchung) that the VM and JFR need 
> no longer distinguish between hidden and unsafe anonymous classes when 
> gathering CLD statistics and when CLD's are displayed in JFR events.  
> Instead, unsafe anonymous classes will be counted as hidden classes 
> for CLD statistics, and JFR will show CLD's for both hidden and unsafe 
> anonymous classes as hidden.
>
> Open Webrev: 
> http://cr.openjdk.java.net/~hseigel/bug_8243572/webrev/index.html
>
> JBS Bugs: https://bugs.openjdk.java.net/browse/JDK-8243572 and 
> https://bugs.openjdk.java.net/browse/JDK-8243336
>
> The fix was regression tested by running Mach5 tiers 1 and 2 tests and 
> builds on Linux-x64, Solaris, Windows, and Mac OS X, by running Mach5 
> tiers 3-5 tests on Linux-x64, and running tier 7 tests multiple times 
> on Windows and also on Mac OS X.  Tier 7 testing on Linux-X64 is in 
> progress.
>
> Thanks, Harold
>