RFR (S): 8218939: vm/mlvm/anonloader/stress/byteMutation crashed on windows

[David Holmes]

Hi Igor,

Thanks for looking at this.

On 15/02/2019 10:20 am, Igor Ignatyev wrote:
> Hi David,
> 
> the fix looks good to me. does it make sense to harden the test and assert the message?

In what way would you harden the test? It does random byte writes which 
could possibly still result in a legal classfile. You'd actually have to 
control the modifications to trigger specific errors that could be 
asserted. And I would expect such tests live somewhere in the JCK already.

Thanks,
David
-----

> -- Igor
> 
>> On Feb 14, 2019, at 2:58 PM, David Holmes <david.holmes at oracle.com> wrote:
>>
>> webrev: http://cr.openjdk.java.net/~dholmes/8218939/webrev
>> bug: https://bugs.openjdk.java.net/browse/JDK-8218939
>>
>> The bytes() in a Symbol are UTF8 but do not form a NUL-terminated C-string. In a couple of places in the classfile parser we are treating it as NUL-terminated:
>>
>> - in name validation we were calling strchr to find the semi-colon, but this could run off through memory if there was no semi-colon (as per the testcase). This is replaced with memchr which takes the expected length.
>>
>> - in formatting the exception message we used %s but instead we need %.*s and pass the length
>>
>> There's a minor change to a test to print the exception information as that exposes the fact we were doing things incorrectly e.g:
>>
>> java.lang.ClassFormatError: Illegal class name "p1//BadInterface1\u00f1\u00ab\u00ab\u00ab\u00ab\u00ab\u00ab\u00ab\u00ab\u00ab\u00ab\u00ab\u00ab\u00ab\u00ab\u00ab\u00abU" in class file
>>
>> versus (after bug fix)
>>
>> java.lang.ClassFormatError: Illegal class name "p1//BadInterface1" in class file UseBadInterface1
>>
>> Testing:
>> - re-ran failing test on Windows with seeds known to have caused failures
>> - ran ran failing test on Windows 150 times with random seeds
>> - tiers 1-3
>>
>> Thanks,
>> David
>> -----
>