Re: Mistake when interface extends interface

Pierre,

  You are quoting the Java language specification, but ASM works at the 
bytecode level, which is very loosely coupled with the high-level language.
  In short, in the bytecode, the interface can't have a parent class, so 
javac is compiling Java's "extends" for interfaces into a list of 
intefaces. Also note that you can't have multiple parent classes for a 
class, but you can for an interface.
  All in all, the ASM framework just literally interprets the bytecode 
for you.

  regards,
  Eugene


Pierre Caserta wrote:
> Hi,
> it seems impossible to know when an interface inherit another 
> interface with ASM, because the extends clause is treated like an 
> implements clause when parsing an interface.
> This is very problematic because interface that extends other 
> interface have a particular semantic:
>
> Chapter 9.1.2 of the java sun docs second edition :
>
>
>       9.1.2 Superinterfaces and Subinterfaces
>
> If an |extends| clause is provided, then the interface being declared 
> extends each of the other named interfaces and therefore inherits the 
> member types, methods, and constants of each of the other named 
> interfaces. These other named interfaces are the /direct 
> superinterfaces/ of the interface being declared. Any class that 
> |implements| the declared interface is also considered to implement 
> all the interfaces that this interface |extends|.
>
>       /ExtendsInterfaces:
>       /	extends /InterfaceType
>       	ExtendsInterfaces , InterfaceType
>
>
>       /
>
> Bellow I give an example and explain the problem.
>
> The javadoc of the visit method of the ClassVisitor says :
> void *visit*(int version,
>            int access,
>            java.lang.String name,
>            java.lang.String signature,
>            java.lang.String superName,
>            java.lang.String[] interfaces)
> Visits the header of the class.
> *Parameters:*
> |superName| - the internal of name of the super class (see 
> |getInternalName| 
> <http://asm.ow2.org/jdiff153to223/ASM%202.2.3/org/objectweb/asm/Type.html#getInternalName%28%29>). 
> For interfaces, the super class is |Object|. May be null, but only for 
> the |Object| class.
> ----------------------
> For instance I take the "java/util/List" Interface that extends the 
> "java/util/Collection" interface.
>
> The visit method will have :  superName  = "java/lang/Object"
> interfaces = {"java/util/Collection"}
> That is wrong!
> It is like if the extends clause is simply replaced by an implements 
> clause, which is not the same.
>
> Does someone have a solution to know if an interface is extending (and 
> not implementing) another interface with asm?
>
> -- 
> Pierre Caserta, Ph.D. Candidate        | Email:  [email protected]
> Nancy-Université INPL / LORIA,         | Phone:  (+33) (0)3 54 95 86 18
> Office C-123,                          | Mobile: (+33) (0)6 76 58 29 42
> 615 Rue du Jardin Botanique, CS 20101  | Web:    www.loria.fr/~casertap
> 54603 VILLERS-LES-NANCY Cedex, FRANCE  | 
>

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