Can virtual function be called inside member initializer lists?

Question

effective c++ item 9

Can function createLogString be virtual?

class BuyTransaction: public Transaction {  
　public:  
　　BuyTransaction( parameters ):Transaction(createLogString(parameters)) { ... }
　　...   
　private:  
　　static std::string createLogString( parameters );  
};

Possible duplicate of [Calling virtual functions inside constructors](https://stackoverflow.com/questions/962132/calling-virtual-functions-inside-constructors) — Alan Birtles, Jan 22 '19 at 08:15
It's not allowed to have both `static` and `virtual`, so here we all assume that you want to change the static function into a virtual function. — Bentoy13, Jan 22 '19 at 08:42

StoryTeller - Unslander Monica · Accepted Answer · 2019-01-22T10:47:31.510

5

Yes, it can be virtual (instead of static). It will still be statically bound during construction however, and not dispatched dynamically.

The only point to making it virtual is if it is also used in some other member of the class (that is not a constructor/destructor) and a deriving class can possibly override it to do something useful for those members. However, that starts having the faint traces of a design smell.

Scott's advice of "Never call virtual functions during construction or destruction" stems from the fact that it rarely if ever accomplishes anything useful.

edited Jan 22 '19 at 10:47

answered Jan 22 '19 at 07:58

StoryTeller - Unslander Monica

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So it will make no sense if we implement the virtual function in some child class of BuyTransaction because BuyTransaction's member initializer list will still call its own createLogString when initializing that child class? – Bowen Fu Jan 22 '19 at 08:14
@BowenFu - Exactly. – StoryTeller - Unslander Monica Jan 22 '19 at 08:15
4

I prefer this answer than the one linked as duplicate which is too lengthy and too strict. Inside a constructor, all member function call are equivalent to a qualified call. – Oliv Jan 22 '19 at 08:28
1

*Never call virtual functions during construction or destruction*. Clang static analyzer even has checks to spot these behaviors. – OrenIshShalom Jan 22 '19 at 08:32
Um... but it's `static`? Or do OP and yourself mean replacing `static` with `virtual`? – Quentin Jan 22 '19 at 10:45
@Quentin - That's how I understood the question. Didn't really give it a second thought, tbh. – StoryTeller - Unslander Monica Jan 22 '19 at 10:46
Fair enough. -- – Quentin Jan 22 '19 at 10:47
Won't it be bound to the type of the constructor's init list you call the function? As in, if there is a parent class that declares it virtual, and the current class overrides it, the override will be called, no? As @Oliv says in his/her comment. – rubenvb Jan 22 '19 at 11:06
1

@rubenvb - That's what "bound statically" meant. Name lookup is based on scope. – StoryTeller - Unslander Monica Jan 22 '19 at 11:19

Can virtual function be called inside member initializer lists?

1 Answers1