Re: [Jikesrvm-researchers] class loader type identifiers question (fwd)

[Adam W. <we...@cs...>]

Hello,
and thank you - that clarified the usage of VM_Types and 
VM_TypeRefeerences. However I still do not understand the usage of the 
following methods: VM_TypeReference.getTypeRef() and VM_Type.getType(). In 
class VM_ExceptionTable they are used in the same context (to obtain type 
of the exception from the exception table) - lines 47 and 74 in the file 
VM_ExceptionTable.java. Both methods perform similar action - consult 
mapping called types but in different (their respective) classes . Do 
these mappings overlap (partially or fully)? Can they be used interchangeably 
(as suggested by the example above)? In other words - if I want to get the 
exception type from the exception table which method should I use (or it 
does not matter)?

Thank you

Adam


> Subject: Re: [Jikesrvm-researchers] class loader type identifiers question
> 
> Hi,
> 
>         VM_TypeReferences are used to represent the reference to a type
> from a class file.  VM_Types are the actual "real" types that the
> references have been resolved into.  In general, the compilers use
> VM_TypeReferences (because in general the reference can't be resolved to a
> real type without involving a classloader or two and we can't do that at
> compile time).
> 
>         If you have an object in hand, then you can get always VM_Type for
> that object, since the type must exist.
> 
>         One thing that might be confusing is that every VM_Type has a
> canonical VM_TypeReference that is the pair of the class name and the
> defining class loader for that VM_Type instance.  This lets one map from
> VM_Types to VM_TypeReferences.
> 
>         There may be a number of VM_TypeReferences that all resolve to the
> same VM_Type.
> 
>         The complexity here is due to classloaders.
> 
> --dave
> 

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Adam Welc
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