[Zeek-Dev] Question about IntrusivePtr and incomplete types

Johanna Amann johanna at corelight.com
Tue Dec 17 07:04:20 PST 2019

>> Is there some way to use an IntrusivePtr in this case - or is is just
>> not possible to use it in cases where it is not possible to use 
>> complete
>> types?
> You should be able to get away with forward declarations as long as 
> you provide matching prototypes for Ref and Unref.

If I do that I get linking errors:

   "Ref(Expr*)", referenced from:
       Expr::Ref() in IdentifierInfo.cc.o
       Expr::Ref() in Expr.cc.o
       Expr::Ref() in ID.cc.o
       WhenStmt::Exec(Frame*, stmt_flow_type&) const in Stmt.cc.o
       Expr::Ref() in Type.cc.o
       Expr::Ref() in Val.cc.o
       make_var(ID*, BroType*, init_class, Expr*, List<Attr*>*, 
decl_type, int) in Var.cc.o
   "Unref(Expr*)", referenced from:
       zeekygen::IdentifierInfo::Redefinition::~Redefinition() in 
       Attr::~Attr() in Attr.cc.o
       UnaryExpr::~UnaryExpr() in Expr.cc.o
       BinaryExpr::~BinaryExpr() in Expr.cc.o
       CondExpr::~CondExpr() in Expr.cc.o
       ScheduleExpr::~ScheduleExpr() in Expr.cc.o
       CallExpr::~CallExpr() in Expr.cc.o

Which makes sense, because Ref/Unref(Expr*) never exist - they only 
exist for BroObj*. I could implement a forward function that does 
nothing besides calling Ref(BroObj) in Expr.cc - but that seems… not 
really elegant/worth using anymore in this case. Unless I an declare 
them in another way that I am missing.


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