By: Gabriele Svelto (gabriele.svelto.delete@this.gmail.com), October 20, 2006 4:38 am
Room: Moderated Discussions
Rob Thorpe (rthorpe@realworldtech.com) on 10/20/06 wrote:
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>* The problem might occur even if the architecture stores values in-order like
>x86 does. The compiler could look at "expensiveInitialisation(AnObject)" and inline
>it into the body of the function. It could then reorder the resulting tree of instructions
>in such a way that the pointer representing the object is updated before the object
>is fully constructed.
This cannot happen in Java, a Java compiler/JIT doing so would alter the semantics of the language which mandates that only the constructor can work on an uninitialized object. Exiting from the constructor makes it initialized and available for other code, the compiler/JIT should enforce this behaviour which is the founding principle of safety in the language.
Gabriele
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>* The problem might occur even if the architecture stores values in-order like
>x86 does. The compiler could look at "expensiveInitialisation(AnObject)" and inline
>it into the body of the function. It could then reorder the resulting tree of instructions
>in such a way that the pointer representing the object is updated before the object
>is fully constructed.
This cannot happen in Java, a Java compiler/JIT doing so would alter the semantics of the language which mandates that only the constructor can work on an uninitialized object. Exiting from the constructor makes it initialized and available for other code, the compiler/JIT should enforce this behaviour which is the founding principle of safety in the language.
Gabriele
