[9] RFR(S): Crash with assert: symbol conversion failure in java_lang_String::create_from_symbol()

[Tobias Hartmann]

Hi,

please review the following patch:
https://bugs.openjdk.java.net/browse/JDK-8164561
http://cr.openjdk.java.net/~thartmann/8164561/webrev.00/

The verification code in java_lang_String::create_from_symbol() that was added by Compact Strings fails because the input symbol does not contain valid UTF8. The problem is that a JCK JNI test passes an invalid UTF8 string as class name to the JNI method "FindClass". In fact, the string contains garbage from reading past array boundaries because of a bug in the test [1]. The JNI spec [2] states that 'name' should be "a fully-qualified class name (that is, a package name, delimited by “/”, followed by the class name). If the name begins with “[“ (the array signature character), it returns an array class. The string is encoded in modified UTF-8".

I nevertheless think that we should not crash in the case of an invalid UTF8 string and therefore disabled the verification code with a comment. We did the same for java_lang_String::create_from_str() [3].

Tested with failing JCK test and JPRT (running).

Thanks,
Tobias

[1] https://bugs.openjdk.java.net/browse/JCK-7307244
[2] https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/functions.html#FindClass
[3] http://hg.openjdk.java.net/jdk9/hs/hotspot/file/d060826d0911/src/share/vm/classfile/javaClasses.cpp#l274