On Wed, Feb 18, 2004 at 10:28:52AM -0700, Andrew Huntwork wrote:
> There are a couple things you could do, one of which may be easy.
>
> First, you could make the instrumentation method you're calling static.
> I assume the verifier error you're getting is that you're trying to do
> a virtual method call on an uninitialized object. Calling a static
> method won't call a method on an object, so you'll be fine.
No, that doesn't work either. It's a different problem to the one
you think. See VM spec section 4.9.4:
"a special type is created and pushed on the verifier's
model of the operand stack as the result of the Java virtual
machine instruction new. The special type indicates the
instruction by which the class instance was created and
the type of the uninitialized class instance created"
The only thing you can do with that object is call the <init>
(contstructor) method. You can't pass it as a parameter to a
profiling routine.
It's quite an irritating restriction.
> Second, you could do some pretty complicated stack and control flow
> analysis. Here's something that's legal in bytecode but not in java:
>
> if(...)
> super(foo);
> else
> super(bar);
Are you sure that's legal? The VM spec says:
"If a constructor body does not begin with an explicit
constructor invocation and the constructor being declared
is not part of the primordial class Object, then the
constructor body is implicitly assumed by the compiler to
begin with a superclass constructor invocation "super();",
an invocation of the constructor of the direct superclass
that takes no arguments."
Does you example begin with an explicit constructor invocation?
I don't think it does. Is it allowed to call two different
constructors for the same class on an object?
> and here's something else that's legal in bytecode
>
> void <init>(Object foo) {
> aload_0
> aload_1
> astore_0
> dup
> invokespecial <init>()V
> astore_1
> return
> }
Does anyone do that?
--
Erik Corry I'd be a Libertarian, if they weren't all a
[EMAIL PROTECTED] bunch of tax-dodging professional whiners. - B. Breathed.
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