RFR (L, final): 8218626: Add detailed message to NullPointerException describing what is null.

[Lindenmaier, Goetz]

Hi Thomas, 

thanks for pointing this out.  I improved the placement 
of the ResourceMarks. 
Unfortunately, base() returns an immutable string, but
for trim_well_known_class_names this does not work.
So I'd propose this: 
http://cr.openjdk.java.net/~goetz/wr19/8218628-exMsg-NPE/17-incremental/
http://cr.openjdk.java.net/~goetz/wr19/8218628-exMsg-NPE/17/

Best regards,
  Goetz.

> -----Original Message-----
> From: Thomas Stüfe <thomas.stuefe at gmail.com>
> Sent: Dienstag, 17. September 2019 09:06
> To: Lindenmaier, Goetz <goetz.lindenmaier at sap.com>
> Cc: Hotspot dev runtime <hotspot-runtime-dev at openjdk.java.net>; Java Core
> Libs <core-libs-dev at openjdk.java.net>
> Subject: Re: RFR (L, final): 8218626: Add detailed message to
> NullPointerException describing what is null.
> 
> Additionally, since 8224193, stringStream does not use RA anymore, so you do
> not need ResourceMarks for the backing buffer. 8224193 has been backported
> to 11, btw.
> 
> On Mon, Sep 16, 2019 at 2:53 PM Thomas Stüfe <thomas.stuefe at gmail.com
> <mailto:thomas.stuefe at gmail.com> > wrote:
> 
> 
> 	Hi Goetz,
> 
> 	not a full review, just a small suggestion. In jvm.cpp you could just
> access ss->base() instead of ss->as_string() since the internal buffer is already
> NULL terminated and result_string does not outlive the stringStream object.
> Also it misses including ostream.hpp.
> 
> 	Cheers, Thomas
> 
> 
> 	On Tue, Sep 10, 2019 at 4:46 PM Lindenmaier, Goetz
> <goetz.lindenmaier at sap.com <mailto:goetz.lindenmaier at sap.com> > wrote:
> 
> 
> 		Hi,
> 
> 		the subject should mention 8218628. (Not 8218626).
> 		Sorry for this!
> 
> 		Best regards,
> 		  Goetz.
> 
> 		From: Lindenmaier, Goetz
> 		Sent: Dienstag, 10. September 2019 11:48
> 		To: 'Hotspot dev runtime' <hotspot-runtime-
> dev at openjdk.java.net <mailto:hotspot-runtime-dev at openjdk.java.net> >; Java
> Core Libs <core-libs-dev at openjdk.java.net <mailto:core-libs-
> dev at openjdk.java.net> >
> 		Subject: RFR (L, final): 8218626: Add detailed message to
> NullPointerException describing what is null.
> 
> 		Hi,
> 
> 		this is the implementation of JEP 358: Helpful
> NullPointerExceptions.
> 
> 		The JEP is in status "Candidate". Coleen (many, many thanks!)
> ran
> 		it through the Oracle-internal processes.  Now I please need
> final reviews
> 		for this change so that I can propose it to target jdk 14.
> 
> 		JEP: https://bugs.openjdk.java.net/browse/JDK-8220715
> 		Enhancement: https://bugs.openjdk.java.net/browse/JDK-
> 8218628
> 		webrev: http://cr.openjdk.java.net/~goetz/wr19/8218628-
> exMsg-NPE/16/
> 
> 		The change ran through a lot of testing, all jtreg and jck tests to
> name
> 		only some. The webrev points to patch
> 		http://cr.openjdk.java.net/~goetz/wr19/8218628-exMsg-
> NPE/16/enable_NPE_message.patch
> 		that enables the change by default,  which was useful for
> testing to
> 		assure the code is used in the tests.
> 		I just pushed the change to jdk/submit once more.
> 
> 		Please review.
> 
> 		Thanks!
> 		  Goetz.
>