RawData ?

[Michael Koch]

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Am Dienstag, 8. April 2003 21:08 schrieb Andrew Haley:
> Tom Tromey writes:
>  > >>>>> "Michael" == Michael Koch <konqueror@gmx.de> writes:
>  >
>  > Michael> Execept the copyright statement and package name both
>  > java Michael> files are identical. Thats why I thought they
>  > could be Michael> merged.
>  >
>  > I've been wondering, but haven't yet brought up, whether this is
>  > something Classpath really wants to do.  It imposes a cost on
>  > all implementing VMs, and compilers.
>  >
>  > Note that we don't even handle RawData properly -- for instance
>  > I think `Object foo = <Rawdata>' should be invalid.  Any cast to
>  > RawData should also be rejected by the compiler.
>
> Yes.  Some code assumes that everything is a subclass of Object and
> so we don't need to check the cast.  This is a good optimization.
> RawData breaks the type system in this regard.
>
>  > Likewise the interpreter and verifier probably need special
>  > cases here.  There may be other problems, in reflection or JNI. 
>  > I'm not sure.
>  >
>  >
>  > Hmm, maybe we should get rid of it and use long :-)
>
> I'm wondering if it might be a good idea to have a type which is
> the equivalent of "integer attribute ((mode(pointer)))" or
> somesuch. However, it wouldn't need to be an arithmetic type.
>
> We could then replace all instances of RawData with that.  We
> wouldn't be able to use it for an IdentityHashmap key, which would
> be a shame.
>
>  > If Classpath does continue with this, we could consider
>  > changing.  A patch to do this would also have to change the
>  > compiler (that's easy in this case though).
>
> Seems reasonable.

It is possible to use long instead of RawData. But then we need 
conversion methods I think (void* -> jlong, jlong -> void*). With 
RawData we can just use a <reinterpret_cast> which has more ore less 
no cost at runtime.

As I understand it using long is in general more safe in regard to 
security holes, right ? We will have to do a lot of work to make sure 
we are on the safe side when we use RawData overall.


Michael
- -- 
Homepage: http://www.worldforge.org/
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