RFR: 8230743 - StringJoiner does not handle too large strings correctly

[Jim Laskey]

Revised with requested changes.


http://cr.openjdk.java.net/~jlaskey/8230743/webrev-01 <http://cr.openjdk.java.net/~jlaskey/8230743/webrev-01>


> On Jun 1, 2020, at 5:32 PM, Paul Sandoz <paul.sandoz at oracle.com> wrote:
> 
> 
> 
>> On Jun 1, 2020, at 12:44 PM, Jim Laskey <james.laskey at oracle.com <mailto:james.laskey at oracle.com>> wrote:
>> 
>> 
>> 
>>> On Jun 1, 2020, at 4:28 PM, Paul Sandoz <paul.sandoz at oracle.com <mailto:paul.sandoz at oracle.com>> wrote:
>>> 
>>> Can we consolidate the use of Integer.MAX_VALUE - 8 in tests by referring to the constant jdk.internal.util.ArraysSupport.MAX_ARRAY_LENGTH?
>> 
>> I suppose  it's possible to add module for java.base/jdk.internal.util.ArraysSupport to the tests.
>> 
>> The mission here was to provide useful error messages. If we're going to clean up growing arrays throughout the JDK, I feel that is a separate mission, probably not something that we should be doing just before RD1.
>> 
> 
> Ok.
> 
> 
>> We should probably have gone one step further with jdk.internal.util.ArraysSupport.newLength and just defined  jdk.internal.util.ArraysSupport.growArray(array, newSize, () -> { // exception code });
> 
>> 
>>> 
>>> 
>>> StringJoiner.java
>>> —
>>> 
>>> 164     @Override
>>> 165     public String toString() {
>>> 166         final String[] elts = this.elts;
>>> 167         if (elts == null && emptyValue != null) {
>>> 168             return emptyValue;
>>> 169         }
>>> 170         final int size = this.size;
>>> 171         final int addLen = prefix.length() + suffix.length();
>>> 172         if (len < 0 || len + addLen < 0) {
>>> 
>>> It bothers me that len might be < 0, suggesting a larger issue. Perhaps look at the add method where len is modified?
>> 
>> I thought about it but that would change the behaviour of StringJoiner. An error would be thrown on the add. Existing code that added but then tested length before trying a toString() would fail too soon.
> 
> Or fail at the right point? Lazy String construction by the joiner can be considered an implementation detail.
> 
> A negative len could result in some odd behavior:
> 
> - an incorrect value returned from length(), such as a negative length value.
> 
> - a number of adds could be performed, which one would have resulted in an OOME if the implementation was not lazy?
> 
> - (len + other.len < 0) could be positive and result in array construction exception for a negative length on other.compactElts.
> 
> Paul.
> 
>> 
>>> 
>>> 
>>> 173             throw new
>>> 174             OutOfMemoryError("Resulting string is exceeds maximum size”);
>>> 
>>> "Resulting string is exceeds… ” -> "Resulting string exceeds… "
>> 
>> Oops, thanks.
>> 
>> 
>>> 
>>> Paul.
>>> 
>>> 
>>>> On Jun 1, 2020, at 8:55 AM, Jim Laskey <james.laskey at oracle.com> wrote:
>>>> 
>>>> Change NegativeArraySizeException to OutOfMemoryError. Tests added.
>>>> 
>>>> Cheers,
>>>> 
>>>> -- Jim
>>>> 
>>>> webrev: http://cr.openjdk.java.net/~jlaskey/8230743/webrev-00/index.html <http://cr.openjdk.java.net/~jlaskey/8230743/webrev-00/index.html>
>>>> jbs: https://bugs.openjdk.java.net/browse/JDK-8230743 <https://bugs.openjdk.java.net/browse/JDK-8230743>