On Fri, 4 Dec 2020 15:47:51 GMT, Roger Riggs <rri...@openjdk.org> wrote:
>> This rewrites the doc of ArraysSupport.newLength, adds detail to the
>> exception message, and adds a test. In addition to some renaming and a bit
>> of refactoring of the actual code, I also made two changes of substance to
>> the code:
>>
>> 1. I fixed a problem with overflow checking. In the original code, if
>> oldLength and prefGrowth were both very large (say, Integer.MAX_VALUE), this
>> method could return a negative value. It turns out that writing tests helps
>> find bugs!
>>
>> 2. Under the old policy, if oldLength and minGrowth required a length above
>> SOFT_MAX_ARRAY_LENGTH but not above Integer.MAX_VALUE, this method would
>> return Integer.MAX_VALUE. That doesn't make any sense, because attempting to
>> allocate an array of that length will almost certainly cause the Hotspot to
>> throw OOME because its implementation limit was exceeded. Instead, if the
>> required length is in this range, this method returns that required length.
>>
>> Separately, I'll work on retrofitting various call sites around the JDK to
>> use this method.
>
> src/java.base/share/classes/jdk/internal/util/ArraysSupport.java line 654:
>
>> 652: return SOFT_MAX_ARRAY_LENGTH;
>> 653: } else {
>> 654: return minLength;
>
> Isn't this last `else if... then.. else` the same as:
> `return Math.max(minLength, SOFT_MAX_ARRAY_LENGTH)`
It is, and I considered replacing it, but I felt that it obscured what was
going on.
-------------
PR: https://git.openjdk.java.net/jdk/pull/1617
