RFR (XS) JDK-8041918: BootstrapMethods attribute cannot be empty

Lois Foltan lois.foltan at oracle.com
Mon May 12 13:03:51 UTC 2014


Please review new updated webrev for this bug that takes into account 
all of Harold's suggested changes, including the test just checking for 
"java.lang.ClassFormatError".  After mulling it over a bit, that did 
seem to make sense.



On 5/9/2014 10:51 AM, Lois Foltan wrote:
> On 5/9/2014 10:27 AM, harold seigel wrote:
>> Hi Lois,
>> Could TestEmptyBootstrapMethodsAttr.java, just check for 
>> "java.lang.ClassFormatError"?  Then the test would not break if the 
>> rest of the message changed.
> Hi Harold,
> Thanks for the review.  I can do that, but would prefer not to. It 
> allows the test to verify specifically the boundary condition of an 
> attribute_length of 2.  If the message is changed in the future, it 
> would be pretty obvious why the test is failing.
>> I think the .jcod files need copyright statements.  Also, could you 
>> add a small comment about what each one does.
> Will do.
> Lois
>> Thanks, Harold
>> On 5/9/2014 10:22 AM, Lois Foltan wrote:
>>> Hello,
>>> Please review the following fix:
>>> Webrev:
>>>     http://cr.openjdk.java.net/~lfoltan/bug_jdk8041918/
>>> Bug: BootstrapMethods attribute cannot be empty
>>>     https://bugs.openjdk.java.net/browse/JDK-8041918
>>> Summary of fix:
>>> JVMS 8, section 4.7.23 details the BootstrapMethods attribute. In 
>>> particular, page 155, describes the "attribute length" field of a 
>>> BootstrapMethods attribute by documenting, "the value of the 
>>> attribute_length item indicates the length of the attribute, 
>>> excluding the initial six bytes."  Thus, a valid BootstrapMethod 
>>> attribute could have an empty bootstrap_methods table where the 
>>> num_bootstrap_methods field is equal to zero.  This situation would 
>>> set the attribute_length legitimately to 2.  The class format check 
>>> within ClassFileParser::parse_classfile_bootstrap_methods_attribte() 
>>> must check for attribute_byte_length to be greater than or equal to 
>>> the sizeof(u2). This check was added post JDK 8, an empty 
>>> bootstrap_methods table was accepted by JDK 8 without generating a 
>>> ClassFormatError.  Thank you to Harold Seigel for helping to figure 
>>> out the .jcod files to yield a reproducer for this bug.
>>> Tests:
>>>     Hotspot's jtreg tests, JCK lang & vm, JDK lang & util, 
>>> vm.quick.testlist
>>> Thank you,
>>> Lois

More information about the hotspot-runtime-dev mailing list