[antlr-interest] Stack fault in destructor of ASTRef.

[Paul Leaman]

Apologies if this is a known problem. I've been trying to use 2.7.5 with the 
SqlSQL2 grammar and have been getting a stack fault in the destructor of 
ASTRef.

It looks like ASTRefs can point to themselves. I haven't gone in deep enough 
to work out why. The following change seems to fix this:

ASTRef::~ASTRef()
{
	if ( ptr->ref != this )
	{
		delete ptr;
	}
}

This also happens in 2.7.6.

Regards,


Paul