RFR: 8256726: Zero: print proper message in ArrayIndexOutOfBoundException

[Aleksey Shipilev]

On Fri, 27 Nov 2020 09:03:58 GMT, Severin Gehwolf <sgehwolf at openjdk.org> wrote:

>> Manifests on tier1 test:
>> 
>> $ CONF=linux-x86_64-zero-fastdebug make run-test TEST=runtime/exceptionMsgs/ArrayIndexOutOfBoundsException/
>> test ArrayIndexOutOfBoundsExceptionTest.testAIOOBMessages(): failure
>> java.lang.AssertionError: expected [Index -5 out of bounds for length 0] but found [-5]
>> 
>> Fix does similar thing to what `Runtime1::throw_range_check_exception` does, but using a safer `jio_snprintf`.
>> 
>> Additional testing:
>>  - [x] AIOBB tests on Linux x86_64 Zero fastdebug
>
> src/hotspot/share/interpreter/zero/bytecodeInterpreter.cpp line 1504:
> 
>> 1502:       arrayOop arrObj = (arrayOop)STACK_OBJECT(arrayOff);                      \
>> 1503:       jint     index  = STACK_INT(arrayOff + 1);                               \
>> 1504:       char message[2 * jintAsStringSize + 35];                                 \
> 
> What's this magic `35` here? `strlen("Index A out of bounds for length B") + 1 == 35`. Isn't this counting the integers twice?
> 
> Consider adding a comment.

Seems OK to overestimate a bit. That's what `Runtime1::throw_range_check_exception` does in C1, so I have not challenged it:
https://github.com/openjdk/jdk/blob/2f06893a29fba3b40cc1cf03095b75b217d1bb93/src/hotspot/share/c1/c1_Runtime1.cpp#L668-L671

It should count the integers twice, because there are two integers in the string.

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PR: https://git.openjdk.java.net/jdk/pull/1341