Lambda and multi-catch

[Sam Pullara]

It is throwing an NPE when he dereferences the null o -- I thought the same
thing the first time I looked at it.

Sam



On Thu, Mar 6, 2014 at 9:15 PM, David Holmes <david.holmes at oracle.com>wrote:

> On 6/03/2014 9:29 PM, Remi Forax wrote:
> > A colleague of mine have find a hairy bug,
> > here is a simple code to reproduce it.
> >
> > import java.io.IOException;
> >
> > public class FunWithMultiCatch {
> >     public static void main(String[] args) {
> >       Runnable r = () -> {
> >         try {
> >           Object o = null;
> >           o.getClass();
> >           throw new IOException();
> >         } catch(IOException | IllegalArgumentException e) {
> >           System.out.println("KO !");
> >         } catch(RuntimeException e) {
> >           System.out.println("OK !");
> >         }
> >       };
> >       r.run();
> >     }
> > }
> >
> > It prints 'KO !' :(
>
> What am I missing? We throw IOException and have a catch block for
> IOException so I would expect it to print "KO !".
>
> I'm more surprised that a non-lambda version prints "OK !"
>
> > The problem can be reproduced for any multi-catch inside a lambda,
> > the exception table is clearly wrong, the IOException and IAE are merged
> > to their common supertype (java.lang.Exception).
>
> That would definitely seem wrong, but more of an issue with catching
> RuntimeExceptions in the first block that should be handled by the
> second catch block. eg change it to throw IllegalStateException() instead:
>
> if (false) throw new IOException();
> throw new IllegalStateException();
>
> -> "KO !"   !!!WT!
>
> David
> -----
>
> > private static void lambda$main$0();
> >       Code:
> >          0: aconst_null
> >          ...
> >         14: athrow
> >         15: astore_0
> >         16: getstatic     #8                  // Field
> > java/lang/System.out:Ljava/io/PrintStream;
> >         19: ldc           #9                  // String OK !
> >         21: invokevirtual #10                 // Method
> > java/io/PrintStream.println:(Ljava/lang/String;)V
> >         24: goto          36
> >         27: astore_0
> >         28: getstatic     #8                  // Field
> > java/lang/System.out:Ljava/io/PrintStream;
> >         31: ldc           #12                 // String KO !
> >         33: invokevirtual #10                 // Method
> > java/io/PrintStream.println:(Ljava/lang/String;)V
> >         36: return
> >       Exception table:
> >          from    to  target type
> >              0    15    15   Class
> > java/lang/Exception                            <------------ Oops
> >              0    15    27   Class java/lang/RuntimeException
> >
> > The current workaround is to not use a multi-catch in a lambda.
> >
> > It seems that some version of Eclipse had the same issue but it's fixed
> > with the one I use (from 21 feb).
> >
> > cheers,
> > Rémi
> >
> >
>
>