RFR (S): 8019192: StringIndexOutOfBoundsException: in Class.getSimpleName()

[Christian Thalinger]

On Sep 26, 2013, at 1:22 AM, Peter Levart <peter.levart at gmail.com> wrote:

> On 09/26/2013 01:27 AM, Christian Thalinger wrote:
>> http://cr.openjdk.java.net/~twisti/8019192/webrev/
>> 
>> 8019192: StringIndexOutOfBoundsException: in Class.getSimpleName()
>> Reviewed-by:
>> 
>> This is a race in MemberName's name and type getters.
>> 
>> MemberName's type field is of type Object so it can hold different objects when it gets filled in from the VM.  These types include String and Object[].  On the first invocation the current type if it's not MethodType gets converted to a MethodType.
>> 
>> There is a tiny window where some instanceof check have already been done on one thread and then another thread stores a MethodType.  The following checkcast then fails.
>> 
>> The fix is to make name and type volatile and do the conversion in a synchronized block.  This is okay because it's only done once.
>> 
>> src/share/classes/java/lang/invoke/MemberName.java
>> 
> 
> Hi Christian,
> 
> Wouldn't it be cleaner that instead of just casting and catching ClassCastException, the volatile field 'type' was 1st copied to a local variable and then an instanceof check + casting and returning performed on the local variable. This would avoid throwing ClassCastException even if it is performed only once per MemberName…

Not sure it would be cleaner; depends on the definition of "cleaner".  I had similar code as you describe before but I changed it to catch the exception.  If people have a strong opinion here I can change it back.

> 
> Regards, Peter
>