[8u] RFR backport of JDK-8144732: VM_HeapDumper hits assert with bad dump_len

[Hohensee, Paul]

CSR https://bugs.openjdk.java.net/browse/JDK-8235299 has been approved and the backport lgtm. 

Thanks,
Paul

On 12/3/19, 3:41 PM, "jdk8u-dev on behalf of Hohensee, Paul" <jdk8u-dev-bounces at openjdk.java.net on behalf of hohensee at amazon.com> wrote:

    Thanks, Andrew. I've filed https://bugs.openjdk.java.net/browse/JDK-8235299 for the backport issue and https://bugs.openjdk.java.net/browse/JDK-8235299 for the associated CSR and assigned both to Denghui.
    
    Paul
    
    On 12/3/19, 2:57 PM, "Andrew Hughes" <gnu.andrew at redhat.com> wrote:
    
        
        
        On 06/11/2019 18:07, Hohensee, Paul wrote:
        > I found http://jperfanal.sourceforge.net/java.hprof.txt, which is a thread stack dump that references 1.0.1, is dated Dec 30, 2001, and the dump output is copyright 1998. So 1.0.1 is probably from 1998.
        > 
        > I found a file format spec at http://hg.openjdk.java.net/jdk6/jdk6/jdk/raw-file/tip/src/share/demo/jvmti/hprof/manual.html#mozTocId848088. It's from Java 6, so 1.0.2 was supported then. I also found
        > 
        > https://bugs.openjdk.java.net/browse/JDK-6305542: HPROF binary format needs to support large dumps
        > 
        > for Java 6, and
        > 
        > https://bugs.openjdk.java.net/browse/JDK-6313381: HPROF: agent should generate version 1.0.2 for large heaps
        > 
        > which updated the hprof agent to generate 1.0.2 format files for heaps > 4gb in Java 6, and
        > 
        > https://bugs.openjdk.java.net/browse/JDK-6313383: SA: Update jmap to support HPROF binary format "JAVA PROFILE 1.0.2"
        > 
        > which was shipped in 8u25 in 2014.
        > 
        > So, JDKs/JREs starting with Java 6 can read 1.0.2 files, and the SA can read them starting with 8u25. I don't think we need to worry about using Java 5 to read files generated by Java 8, and the SA is good to go for 8.
        > 
        > Paul
        > 
        
        Thanks for the through research. My concern is not so much whether the
        format can be read, as whether it is expected on small heap dumps.
        JDK-6313383 also says "For compatibility it would be best if jmap
        continued to generate a 1.0.1 format for smaller heaps (<2GB for example).".
        
        I think this may warrant a CSR.
        
        Thanks,
        -- 
        Andrew :)
        
        Senior Free Java Software Engineer
        Red Hat, Inc. (http://www.redhat.com)
        
        PGP Key: ed25519/0xCFDA0F9B35964222 (hkp://keys.gnupg.net)
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