Bug in javac release flag?

[Jan Lahoda]

Hi Stephen,

I was looking at the historical data for 8 and 9 in JDK10, and the JDK 8 
data appears to only declare the two overloads:
http://hg.openjdk.java.net/jdk/jdk10/file/48ce4b11bc17/make/data/symbols/java.base-8.sym.txt#l2361
And the JDK 9 data appears to add the additional overload:
http://hg.openjdk.java.net/jdk/jdk10/file/48ce4b11bc17/make/data/symbols/java.base-9.sym.txt#l525

So these appear to me to be OK.

I also checked the content of the ct.sym, and the sig files in there 
appear to be OK as well - the JDK 8 version contains only two 
[overloads, while the JDK 9 version contains three overloads. So this 
appears to be reasonable.

I also tried to compile and run:
---
public class M {
     public static void main(String... args) {
         System.err.println(Math.floorDiv(0L, 1));
     }
}
---

---
$ javac -fullversion
javac full version "9+181"
$ javac --release 8 M.java
$ java -fullversion
java full version "1.8.0_121-b13"
$ java M
0
---

So that appears to be OK as well.

I tried to compile the project using maven, and in debug output, I was 
able to find "--release 9", but not "--release 8", only "-target 1.8 
-source 1.8". This will produce JDK 8 classfiles, but compile against 
the JDK 9 system modules. To get the new --release behavior, "--release 
<VERSION>" must be used.

Jan

On 22.1.2018 16:34, Jonathan Gibbons wrote:
> Forwarding to compiler-dev, which is a better place to discuss this issue.
>
> -- Jon
>
>
> On 1/22/18 7:11 AM, Stephen Colebourne wrote:
>> I think I have a problem with the java release flag, reported by a
>> user here:
>> https://github.com/ThreeTen/threeten-extra/issues/91
>>
>> The particular case that is a problem are the new methods on
>> java.lang.Math.
>>
>> Java 8 had these methods:
>>   floorDiv(long,long)
>>   floorDiv(int,int)
>>
>> Java 9 has these methods:
>>   floorDiv(long,long)
>>   floorDiv(int,int)
>>   floorDiv(long,int)
>>
>> (there are similar new overloads for other method names)
>>
>> Clearly, if you build on Java 9, code can link to the new(long,int)
>> overload, but that code will get a NoSuchMethodError on Java 8.
>>
>> But, I am using Java 9 with the javac release flag set to be 8. If I
>> understand the release flag correctly, the (long,int) overload should
>> not be visible, and thus a different overload should be selected.
>>
>> So, is this a bug? Perhaps the tool that captures new method
>> signatures doesn't handle overloads?
>>
>> (ThreeTen-Extra v1.3 was built using Maven on Java 9 using Maven's
>> implementation of the release flag, so it could be Maven that is
>> buggy, but I don't think so as it produces the correct classfile
>> version number).
>>
>> thanks
>> Stephen
>