RFR(XS): 8155735: use strings instead of Symbol* in JVMCI exception stubs

[Roland Schatz]

On 04/29/2016 09:49 PM, Tom Rodriguez wrote:
> Sorry I was looking at the comment below lookup instead of above it.  It’s very odd that both of these exist though and new_symbol just forwards to lookup.
>
>    static Symbol* new_symbol(const char* utf8_buffer, int length, TRAPS) {
>    static Symbol* lookup(const char* name, int len, TRAPS);
>
> I do think you want the TempNewSymbol though.
You're right. I misunderstood the semantics of lookup/new_symbol, they 
actually both do the same thing.

Normally, the symbol we're looking up is a class name, so the lookup 
should never fail anyway. But we should still not leak anything if there 
is a wrong string passed in.

New webrev, using TempNewSymbol:
http://cr.openjdk.java.net/~rschatz/JDK-8155735/webrev.01/

I've also included an exception check after the symbol lookup, just to 
be sure.

- Roland
>
>>> and let new_exception throw an exception if the class named by symbol doesn’t exist.
>> throw_and_post_jvmti_exception will throw a `NoClassDefFoundError` when the exception class doesn't exist.
>>
>>
>> Just to be sure, I tested this using graal. Temporarily passing in a wrong class name into the stub results in:
>>> java.lang.NoClassDefFoundError: bla/java/lang/NullPointerException
>>>         at com.oracle.graal.replacements.test.CompiledNullPointerExceptionTest.testSnippet(CompiledNullPointerExceptionTest.java:93)
>>>         at jdk.vm.ci.hotspot.CompilerToVM.executeInstalledCode(Native Method)
>>>         at jdk.vm.ci.hotspot.HotSpotNmethod.executeVarargs(HotSpotNmethod.java:100)
>>>         at com.oracle.graal.compiler.test.GraalCompilerTest.executeActual(GraalCompilerTest.java:578)
>>> […]
> Thanks for checking.
>
> tom
>
>>
>> - Roland
>>