RFR: 8286378: Address possibly lossy conversions in java.base [v2]

[Alan Bateman]

On Tue, 10 May 2022 23:01:33 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

>> PR#8599 8244681: proposes to add compiler warnings for possible lossy conversions
>> From the CSR:
>> 
>> "If the type of the right-hand operand of a compound assignment is not assignment compatible with the type of the variable, a cast is implied and possible lossy conversion may silently occur. While similar situations are resolved as compilation errors for primitive assignments, there are no similar rules defined for compound assignments."
>> 
>> This PR anticipates the warnings and adds explicit casts to replace the implicit casts.
>> In most cases, the cast matches the type of the right-hand side to type of the compound assignment.
>> Since these casts are truncating the value, there might be a different refactoring that avoids the cast
>> but a direct replacement was chosen here.
>> 
>> (Advise and suggestions will inform similar updates to other OpenJDK modules).
>
> Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:
> 
>   remove stray file

src/java.base/linux/classes/sun/nio/ch/EPollSelectorImpl.java line 128:

> 126:                     // timed poll interrupted so need to adjust timeout
> 127:                     long adjust = System.nanoTime() - startTime;
> 128:                     to -= (int)TimeUnit.MILLISECONDS.convert(adjust, TimeUnit.NANOSECONDS);

Can we change this `to =- (int) TimeUnit.NANOSECONDS.toMillis(adjust);` while we here?

src/java.base/share/classes/jdk/internal/org/objectweb/asm/Frame.java line 615:

> 613:         if (outputStackTop >= elements) {
> 614:             outputStackTop -= (short)elements;
> 615:         } else {

I think we usually try to avoid changing the ASM code if possible but maybe you have to do this because the compiler option is used for compiling java.base?

src/java.base/unix/classes/sun/nio/ch/PollSelectorImpl.java line 123:

> 121:                     // timed poll interrupted so need to adjust timeout
> 122:                     long adjust = System.nanoTime() - startTime;
> 123:                     to -= (int)TimeUnit.MILLISECONDS.convert(adjust, TimeUnit.NANOSECONDS);

This one can also be changed to:

`to =- (int) TimeUnit.NANOSECONDS.toMillis(adjust);`

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PR: https://git.openjdk.java.net/jdk/pull/8642