gcj producing bad code

Sat Apr 6 17:39:00 GMT 2002

Nic Ferrier wrote:
>>>GCJ is not compiling method calls quite right... it seems that all 
>>>super invocations are done through invokespecial. invokespecial 
>>>cannot be used when the target needs to be called through virtual 
>>>dispatch however. 
>>>>>>I'm not quite sure you said that right. Any call to super.method() is 
>>required to compile to invokespecial (unless method is static, in which 
>>case invokestatic is appropriate). By the way, in the case of 
>>EnclosingClass.super.method(), it may require the assistance of an 
>>accessor method to use invokespecial while still obeying access rules. 
>>Consider this example, from the point of view of class C: 
>>> The case I'm referring to is a metjod invocation on a property of the
> super class, thus:
>> class A
> X x;
> public X getX() { return x; }
>>> class B extends A
> public Y getY() { return super.getX().getY(); }
>>> The method B::getY() must compile to call getY() through a virtual
> dispatch even though X is in super.

The getY() isn't a super invocation - it's the same as
 (super.getX()).getY()
or even:
 X t = super.getX();
 return t.getY();
If we're emitting invokespecial to call getY, then I don't think
the flaw in actually in the bytecode-generation, but more likely
the front-end (resolve_qualified_expression_name in parse.y)
incorrectly setting CALL_WITH_SUPER.
I suspect the problem is that the variable 'from_super' isn't
being reset in resolve_qualified_expression_name. Alex?
-- 
	--Per Bothner
per@bothner.com http://www.bothner.com/per/