RFR(M): 8201593: Print array length in ArrayIndexOutOfBoundsException.

[David Holmes]

Hi Goetz,

This is not a file by file review ...

On 19/04/2018 10:24 PM, Lindenmaier, Goetz wrote:
> Hi,
> 
> New webrev:
> http://cr.openjdk.java.net/~goetz/wr18/8201593-lenInAIOOB/02/
> 
> I admit my wording is not optimal.

src/hotspot/share/oops/typeArrayKlass.cpp

Sorry but this is still far too verbose for my tastes. The type of the 
array is not relevant. For the array copy its okay to indicate src or 
dst array. But the message should be clear and succinct not prose-like. 
Plus you have a lot of repetition in the ss.print statements when only 
one thing is changing.

src/hotspot/cpu/x86/c1_CodeStubs_x86.cpp

I'm not seeing why the throw_index_out_of_bounds_exception should be 
tied to whether or not you have an array reference. Certainly I hate 
seeing the array ref being used as an implicit bool!

> It's because I extracted this change from a bigger one. Our message reads like this:
> Object [] oa1 = new Object[10]
> oa1[12]
> "ArrayIndexOutOfBoundsException while trying to load from index 12 of an object array with length 10, loaded from local variable 'oa1'"
> ... which seems not optimal, either. But it mentions the type (object), the operation (load, store etc ...) and the variable name.
> Naming the array is quite detailed if it is in a complex expression (like returned from a call).
> I'll contribute more of this if appreciated, this is a first step.

I've never thought this complexity was warranted. We've had a few RFE's 
of this nature over the years and they have been closed (not necessarily 
by me I should point out!).

> Printing "index N is outside range [0, length-1]" is problematic
> for length '0'. I followed the proposal by Roger:
> "Index -1 out-of-bounds for length 10."

You can easily special-case length 0. But Roger's proposal for 
consistency with existing messages make sense - not withstanding 
Andrew's dislike for the hyphens.

> I removed the change to ArrayIndexOutOfBoundsException.java.

That's good.

> I extended the test to cover the exception thrown in arraycopy better

The test seems somewhat excessive, and I now see it is because of the 
more elaborate error messages you have at SAP. But with only the index 
and the array length of interest here the test can be considerably smaller.

The creation tests for ArrayIndexOutOfBoundsException don't seem 
relevant in this context either. This looks more TCK like.

David
-----

> and added the elementary type to the message text.  This probably
> needs improvement in the text, too.  There are (currently) these cases:
> 
> bject[]  oa1 = new Object[10];
> Object[]  oa2 = new Object[5];
> System.arraycopy(oa1, -17, oa2, 0, 5);
> "while trying to copy from index -17 of an object array with length 10");
> System.arraycopy(oa1, 2, oa2, -18, 5);
> "while trying to copy to index -18 of an object array with length 5");
> System.arraycopy(oa1, 2, oa2, 0, -19);
> "while trying to copy a negative range -19 from an object array with length 10 to an object array with length 5");
> System.arraycopy(oa1, 8, oa2, 0, 5);
> "while trying to copy from index 13 of an object array with length 10");
> System.arraycopy(oa1, 1, oa2, 0, 7);
> "while trying to copy to index 7 of an object array with length 5");
> double[]  ta1 = new double[10];
> double[]  ta2 = new double[5];
> System.arraycopy(ta1, -17, ta2, 0, 5);
> "while trying to copy from index -17 of a doubl array with length 10");
> System.arraycopy(ta1, 2, ta2, -18, 5);
> "while trying to copy to index -18 of a double array with length 5");
> System.arraycopy(ta1, 2, ta2, 0, -19);
> "while trying to copy a negative range -19 from a double array with length 10 to a double array with length 5");
> System.arraycopy(ta1, 8, ta2, 0, 5);
> "while trying to copy from index 13 of a double array with length 10");
> System.arraycopy(ta1, 1, ta2, 0, 7);
> "while trying to copy to index 7 of a double array with length 5");
> 
> Maybe it should say:
> Arraycopy source index -1 out-of-bounds for double array of length 10.
> Arraycopy target index 10 out-of-bounds for object array of length 10.
> Negative range -19 when copying from an object array of length 10 to an object array of length 5.
> 
> Best regards,
>    Goetz.
> 
>> -----Original Message-----
>> From: David Holmes [mailto:david.holmes at oracle.com]
>> Sent: Mittwoch, 18. April 2018 10:55
>> To: Lindenmaier, Goetz <goetz.lindenmaier at sap.com>; hotspot-runtime-
>> dev at openjdk.java.net; hotspot-compiler-dev at openjdk.java.net; aarch64-
>> port-dev at openjdk.java.net; aarch32-port-dev at openjdk.java.net; core-libs-
>> dev Libs <core-libs-dev at openjdk.java.net>
>> Subject: Re: RFR(M): 8201593: Print array length in
>> ArrayIndexOutOfBoundsException.
>>
>> Adding core-libs-dev as you're changing
>> java.lang.ArrayIndexOutOfBoundsException.
>>
>> I appreciate the intent here but I find the messages excessively
>> verbose. The basic error is:
>>
>> index N is outside range [0, length-1]
>>
>> David
>>
>> On 18/04/2018 6:09 PM, Lindenmaier, Goetz wrote:
>>> Hi,
>>>
>>> I would like to print a more verbose text on ArrayIndexOutOfBounds
>> exception
>>> that not only mentions the index, but also the length of the array accessed.
>>> See the bug for documentation of the change of the message.
>>> http://cr.openjdk.java.net/~goetz/wr18/8201593-lenInAIOOB/01/
>>>
>>> @aarch/arm people:
>>> I edited the aarch/arm files. Could you please verify this is correct?
>>> I can not build on these platforms.
>>>
>>> The code on all the other platforms is tested with all the jtreg and jck tests
>> etc.
>>>
>>> Best regards,
>>>     Goetz.
>>>
>>>