RFR(XXS): 8039348: -XX:+TraceDeoptimization -XX:+Verbose -Xcomp can crash VM

Markus Grönlund markus.gronlund at oracle.com
Sun Apr 6 19:07:55 UTC 2014

Actually, now reflecting a bit more on it, since this uncommon trap happens while executing the constructor itself, one could argue that the object instance is not yet created.


In addition, the "normal" representation of the java/lang/String  object in print() is the value of the [C array - so in that case it might very well be that "NULL" is  the value to output, since there is no [C.


I can keep "NULL" as is.






From: Markus Grönlund 
Sent: den 6 april 2014 20:51
To: Staffan Larsen
Cc: serviceability-dev at openjdk.net; hotspot-runtime-dev at openjdk.java.net
Subject: RE: RFR(XXS): 8039348: -XX:+TraceDeoptimization -XX:+Verbose -Xcomp can crash VM


Yes. The java/lang/String object is not NULL but it's [C field is.


In the local/expression slots output, there is an object there, it's not NULL, it's being created.




From: Staffan Larsen 
Sent: den 6 april 2014 20:24
To: Markus Grönlund
Cc: HYPERLINK "mailto:serviceability-dev at openjdk.net"serviceability-dev at openjdk.net; HYPERLINK "mailto:hotspot-runtime-dev at openjdk.java.net"hotspot-runtime-dev at openjdk.java.net
Subject: Re: RFR(XXS): 8039348: -XX:+TraceDeoptimization -XX:+Verbose -Xcomp can crash VM


You have changed the output when the 'value' field is not set from NULL to "". Was this intentional?




On 6 apr 2014, at 19:05, Markus Grönlund <HYPERLINK "mailto:markus.gronlund at oracle.com"markus.gronlund at oracle.com> wrote:




Kindly asking for reviews for this small fix:


Bug: https://bugs.openjdk.java.net/browse/JDK-8039348

Webrev: http://cr.openjdk.java.net/~mgronlun/8039348/webrev01/


Found when debugging:

-XX:+TraceDeoptimization -XX:+Verbose -Xcomp


Using -Xcomp can cause an uncommon trap in java/lang/String constructors before the [C value field has been assigned.




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