[External] : Re: Classfile API cleanup of labelToBci from CodeModel and CodeBuilder and removal of impl.LabelResolver

[Michael van Acken]

Am Fr., 19. Aug. 2022 um 09:58 Uhr schrieb Adam Sotona <
adam.sotona at oracle.com>:

>
>
>
>
> *From: *Michael van Acken <michael.van.acken at gmail.com>
>
> I was referring to the part where the code of the finally block is
> duplicated
>
> into all paths right after their respective handled regions.  Looking at
> the
>
> CodeBuilder source code, I can't find any of this.
>
>
>
> This is an example use case of CodeBuilder::trying:
>
>      codeBuilder.trying(tryBuilder -> {
>
>          // try block code
>
>      }, catchBuilder -> {
>
>          catchBuilder.catching(CD_IOOBE, handlerBuilder -> {
>
>              // catch handler code can
>
>          }).catchingAll(finallyBuilder -> {
>
>              // finally handler code
>
>          });
>
>      });
>

I tried to follow your suggestion, but was not able to complete the
try/finally output.
The Clojure code is probably not that helpful here, but if I put this
method through
javac I get output whose [8, 16[ (right after the region covered by
exceptionCatch)
I cannot emulate with the trying() construction you describe.

  public static void tryFinally() {
    try {
      System.out.println("Hello World!");
    } finally {
      System.out.println("Finally...");
    }
  }

         0: getstatic     #7                  // Field
java/lang/System.out:Ljava/io/PrintStream;
         3: ldc           #13                 // String Hello World!
         5: invokevirtual #15                 // Method
java/io/PrintStream.println:(Ljava/lang/String;)V
         8: getstatic     #7                  // Field
java/lang/System.out:Ljava/io/PrintStream;
        11: ldc           #21                 // String Finally...
        13: invokevirtual #15                 // Method
java/io/PrintStream.println:(Ljava/lang/String;)V
        16: goto          30
        19: astore_0
        20: getstatic     #7                  // Field
java/lang/System.out:Ljava/io/PrintStream;
        23: ldc           #21                 // String Finally...
        25: invokevirtual #15                 // Method
java/io/PrintStream.println:(Ljava/lang/String;)V
        28: aload_0
        29: athrow
        30: return
      Exception table:
         from    to  target type
             0     8    19   any


>
> This method encapsulates a BlockCodeBuilder instance, but does not
>
> provide it to the caller (the `child` below):
>
>
>
> This is an example use case of CodeBuilder::block:
>
>
>
>      codeBuilder.block(blockBuilder -> {
>
>          // block code
>
>
>
>          if( blockBuilder.isEmpty()) …
>
>      });
>

This is extremely helpful.  I can either transport the isEmpty() status via
side-effect
out of the closure (ugly), or wrap the whole t/c/f in this block()
(probably better).  In
either case I can get rid of my labelToBci calls.  Right now I have to cast
to
BlockCodeBuilderImpl to get to isEmpty().

-- mva
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