PING: Re: Fix build failure with JAVAC_MAX_WARNINGS=true in sun/nio/cs

[Andrew Haley]

On 09/06/10 10:11, Andrew John Hughes wrote:
> On 9 June 2010 07:55, Florian Weimer <fweimer at bfk.de> wrote:
>> * Andrew John Hughes:
>>
>>> On 7 June 2010 23:04, Xueming Shen <xueming.shen at oracle.com> wrote:
>>>> Hi Andrew,
>>>>
>>>> 6959197: When building with JAVAC_MAX_WARNINGS=true, the build fails in
>>>> sun/nio/cs due to the use of -Werror
>>>>
>>>> (1)sun/io/ByteTocharISO2022JP.java
>>>>   #129,  #151
>>>>
>>>>   if ((byte1 & (byte)0x80) != 0){
>>>>
>>>>       if ((byte2 & (byte)0x80) != 0){
>>>>
>>>>
>>>> (byte) casting is not necessary as well?
>>>>
>>>
>>> It's necessary.  0x80 is an integer literal
>>> (http://java.sun.com/docs/books/jls/third_edition/html/lexical.html#3.10.1)
>>> which requires a lossy narrowing conversion to byte
>>> (http://java.sun.com/docs/books/jls/third_edition/html/conversions.html#5.1.3)
>>
>> Doesn't the & operator promote its arguments to int anyway?  I don't
>> think the cast to byte makes a difference here because it does not
>> matter if 0x80 is sign-extended or zero-extended.
>>
>> It might be more efficient to use "byte1 < 0" and "byte2 < 0" instead.

This code may be in a critical performance-related place.  It's quite
possible that it's done this way because the JIT compiles it very well.

So, best not to change it without knowing what the effect is.

Andrew.