Request for sponsor: 4421494 infinite loop while parsing double literal

[Dmitry Nadezhin]

Hello Joe,

Thank you for the sponsorship of the bug 4421494.

I can also prepare a fix for another related bug 4396272
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4396272

The bug 4396272 is blinking because it occurs only when HotSpot chooses 
double value set and it doesn't occur
with double-extended-exponent value set.
The suggested fix will be in FloatingDecimal too, though in other line.

What is more convenient to you
a) if I combine both fixes of 4421494 and 4396272 in a single changeset now;
b) if I postpone submitting of the fix 4396272 until 4421494 is in the JDK
?

  -Dima
> Dmitry Nadezhin wrote:
>> http://bugs.sun.com/view_bug.do?bug_id=4421494
>> https://bugs.openjdk.java.net/show_bug.cgi?id=100119
>>
>> Summary: This old bug report says that Double.parseDouble(s) hangs 
>> for decimal strings
>> in range (Double.MIN_NORMAL-0.5*Double.MIN_VALUE,Double.MIN), and 
>> returns
>> incorrect result for decimal string 
>> Double.MIN_NORMAL-0.5*Double.MIN_VALUE.
>>
>> This is because current code in FloatingDecimal.doubleValue() 
>> incorrectly
>> defines the condition when nextDown(dValue) - dValue == 
>> -0.5*ulp(dValue). The
>> current code considers that these are all numbers 2^n which are 
>> represented as
>> normal doubles, and nexDown(dValue) - dValue == -1.0*ulp(dValue) for 
>> other
>> doubles (subnormal or not 2-powers).
>> However, this is not correct for dValue == Double.MIN_VALUE, because
>> nextDown(Double.MIN_NORMAL) - Double.MIN_NORMAL == 
>> -1.0*ulp(Double.MIN_NORMAL).
>>
>> The suggested change
>> -                    if ( (bigIntNBits == 1) && (bigIntExp > 
>> -expBias) ){
>> +                    if ( (bigIntNBits == 1) && (bigIntExp > 
>> -expBias+1) ){
>> redefines the condition so that dValue == Double.MIN_NORMAL doesn't 
>> satisfy it.
>>
>> -Dima
>
> Hello.
>
> Thank you for the proposed fix; that certainly sounds like a plausible 
> cause of the problem.
>
> I'm a bit swamped now, but I'll try to look at verifying the fix and 
> sponsoring getting it back into the JDK within the next few weeks.
>
> -Joe