RFR 8218228 : The constructor StringBuffer(CharSequence) violates spec for negatively sized argument

[Ivan Gerasimov]

Hi Roger!

That's because two tiny changes are combined in the patch:

1) remove a problematic statement from the javadoc, as it doesn't hold 
anyway.  This part does not change the behavior.

2) unify type of the exception thrown for all negative values of 
CharSequence.length().  The regression test is to verify this, second 
change, so it fails prior the fix for length \in [-16, -1].

I can separate them into different bugs, if you think it will make it 
clearer.  Though I thought they can be fixed together.

With kind regards,

Ivan


On 2/8/19 1:49 PM, Roger Riggs wrote:
> Hi Ivan,
>
> In the direction of not changing the behavior; the webrev does change 
> the behavior.
>
> In the case of CharSeqence with length -1..-16, the new behavior 
> throws NegativeArrayIndexException
> instead of java.lang.IndexOutOfBoundsException.
>
>
> AbstractStringBuilder:101-102 throw an exception for length < 0.
> However, the current behavior is to create a StringBuffer with length 
> + 16 and
> then append the contents.  For -1..-16, it will succeed in creating a 
> StringBuffer
> but fail with IndexOutOfBoundsException during the append of the 
> contents.
>
> The new Test should pass both before and after the change to the code.
>
> Roger
>
>
> On 02/07/2019 10:19 PM, Ivan Gerasimov wrote:
>>
>>
>> On 2/7/19 6:33 PM, David Holmes wrote:
>>> On 8/02/2019 11:59 am, Ivan Gerasimov wrote:
>>>> Hi David!
>>>>
>>>>
>>>> On 2/7/19 5:16 PM, David Holmes wrote:
>>>>> Hi Ivan,
>>>>>
>>>>> On 8/02/2019 11:02 am, Ivan Gerasimov wrote:
>>>>>> Hello!
>>>>>>
>>>>>> The specification states:
>>>>>> """
>>>>>> If the length of the specified CharSequence is less than or equal 
>>>>>> to zero, then an empty buffer of capacity 16 is returned.
>>>>>> """
>>>>>>
>>>>>> However, the current implementation throws either 
>>>>>> NegativeArraySizeException or IndexOutOfBounds instead (the 
>>>>>> actual exception type depends on the value of reported negative 
>>>>>> length).
>>>>>
>>>>> How can you have a negative length CharSequence ??
>>>>>
>>>> A custom CharSequence returning negative length() can be created.
>>>> Not sure how useful/popular this may be, though.
>>>
>>> Seems pretty meaningless so just treating that as an error seems 
>>> fine. Though somewhat debatable whether you need to add an 
>>> appropriate @throws.
>>>
>> Right.  There were two reasons not to add @throws here:
>> - by removing the problematic paragraph we just make the javadoc 
>> almost the same as for StringBuilder(CharSequence),
>> - we don't seem to have any other places (at least I couldn't find 
>> any) specifying exceptions due to negatively sized CharSequence.
>>
>> (To be precise, there is one candidate, but I'll file a separate bug 
>> to fix it.)
>>
>>>> That's why I propose just removing the mentioning negative length, 
>>>> and not changing the behavior.
>>>>
>>>> The proposed code change is to only unify the behavior for any 
>>>> negative value of length.
>>>
>>> Ok.
>>>
>>>>> If its an empty CharSequence then it should return the empty 
>>>>> buffer as indicated.
>>>>>
>>>> Empty CharSequence is processed correctly already.
>>>
>>> Okay so by removing this part:
>>>
>>> -      * <p>
>>> -      * If the length of the specified {@code CharSequence} is
>>> -      * less than or equal to zero, then an empty buffer of capacity
>>> -      * {@code 16} is returned.
>>>
>>> you're relying on the main specification to implicitly handle the 
>>> empty case.
>>>
>> Yes.
>>
>> With kind regards,
>> Ivan
>>
>>
>>> David
>>> -----
>>>
>>>> With kind regards,
>>>> Ivan
>>>>
>>>>> Cheers,
>>>>> David
>>>>>
>>>>>> It is proposed to do two things:
>>>>>> 1) remove the problematic sentence from the javadoc (CSR is filed).
>>>>>> 2) unify the exception type thrown, if the argument reports 
>>>>>> negative length.
>>>>>> NegativeArraySizeException will be consistent with, for example, 
>>>>>> StringBuffer(negativeCapacity).
>>>>>>
>>>>>> Would you please help review the fix?
>>>>>>
>>>>>> BUGURL: https://bugs.openjdk.java.net/browse/JDK-8218228
>>>>>> WEBREV: http://cr.openjdk.java.net/~igerasim/8218228/00/webrev/
>>>>>> CRS: https://bugs.openjdk.java.net/browse/JDK-8218649
>>>>>>
>>>>>
>>>>
>>>
>>
>
>

-- 
With kind regards,
Ivan Gerasimov