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List:       openjdk-hotspot-runtime-dev
Subject:    RFR 8175383: JVM should throw NCDFE if ACC_MODULE and CONSTANT_Module/Package are set
From:       harold seigel <harold.seigel () oracle ! com>
Date:       2017-02-27 13:48:55
Message-ID: bc73f7ba-7515-8472-9590-40e0280ca60b () oracle ! com
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Hi,

Please review this fix to throw NoClassDefFoundError exceptions, instead 
of ClassFormatError exceptions, for version 53 or greater class files 
that have ACC_MODULE set in their access_flags and one or more constant 
pool entries of CONSTANT_Module or CONSTANT_Package (19 or 20).  The JVM 
parses the constant pool before parsing the access_flags.  So, it needs 
to save the fact that the constant pool contained an entry of 19 or 20.  
Then, after checking for ACC_Module in the access_flags, decide which 
exception to throw.

To summarize the desired behavior:

    For class file versions < 53 throw CFE for any bad constant pool
    entry regardless of access_flags.

    For class file versions >= 53 throw NCDFE for a bad constant pool
    entry of 19 or 20 and ACC_Module set in access_flags.

    For class file versions >= 53 throw CFE for a bad constant pool
    entry of 19 or 20 and ACC_Module not set in access_flags.

    For class file versions >= 53 throw CFE for a bad constant pool
    entry other than 19 or 20 regardless of access_flags.

The reasoning behind this is that constant pool entries 19 and 20 are 
only valid when ACC_Module is set.  So, if ACC_Module is set then 
constant pool entries 19 and 20 are technically valid and CFE should not 
be thrown.  Instead, a NCDFE is thrown because of ACC_Module.

I moved the check for ACC_MODULE out of verify_legal_class_modifiers() 
for the following reason.  Suppose there's a CONSTANT_Module entry in 
the constant pool and suppose verify_legal_class_modifiers() throws a 
CFE for a reason unrelated to ACC_MODULE.  That could be considered a 
bug because the CFE should be thrown with a message describing the bad 
CONSTANT_Module entry, not the bad access_flags.  If it does not matter 
which CFE gets thrown then the ACC_MODULE check could be moved back into 
verify_legal_class_modifiers().

Open webrev: 
http://cr.openjdk.java.net/~hseigel/bug_8175383/webrev/index.html

JBS Bug: https://bugs.openjdk.java.net/browse/JDK-8175383

The fix was tested with the JCK lang and vm tests, the JTreg hotspot, 
java/io, java/lang, java/util and other tests, the RBT tier2 -tier5 
tests, the colocated and non-colocated NSK tests, and with JPRT.

Thanks, Harold

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