On ecj and @Override annotations for interface methods

[Mark Wielaard]

On Thu, 2008-09-18 at 13:41 +0200, Mark Wielaard wrote:
> On Thu, 2008-09-18 at 23:37 +1200, C. K. Jester-Young wrote:
> > On Thu, Sep 18, 2008 at 01:33:27PM +0200, Mark Wielaard wrote:
> > > There is no -source 1.6 option, there were no language changes between
> > > 1.5 and 1.6, only target changes. (Although -source 1.5 will trigger
> > > -target 1.5, which is why it makes a difference compared to not giving
> > > any -source option.)
> > 
> > There is, for the ecj that comes with Ubuntu 8.04 ("Eclipse Java
> > Compiler v_774_R33x, 3.3.1"). It makes a difference between whether
> > @Override annotations are accepted for interface methods; in fact,
> > that's why I started this thread in the first place. :-)
> 
> O, that is super confusing, since openjdk javac explicitly says -source
> 1.6 is not a valid option. hmmm.

OK, I checked, and it seems openjdk6 javac, actually does accept -source
1.6, this will trigger -target 1.6 though (which I don't think is a good
thing for bootstrapping against other free VMs). javac documentation
however explicitly says:

   -source release
      Specifies  the  version of source code accepted. The following
      values for release are allowed:

      1.3
         The compiler does  not  support  assertions,  generics,  or
         other language features introduced after JDK 1.3.

      1.4
         The compiler accepts code containing assertions, which were
         introduced in JDK 1.4.

      1.5
         The compiler accepts code  containing  generics  and  other
         language features introduced in JDK 5. This is the default.

      5  Synonym for 1.5

    Note: No language changes were introduced in JDK 6, so the values
    1.6 and 6 are not valid.

Also you cannot combine -source 1.6 and -target 1.5:
javac: source release 1.6 requires target release 1.6

I don't know a good way out of this mess. Maybe for icedtea1.7 we should
just require a compiler and runtime that supports both -source and
-target 1.6, but keep icedtea6 on 1.5 to ease bootstrapping with
existing (older) free platforms.

This however doesn't help with our problem that there apparently isn't
any public documentation on all this (neither the source language
changes, not the target byte code changes). Luckily we do now have the
sources though.

Cheers,

Mark