Szelethus added inline comments.
================
Comment at: clang/lib/Analysis/CFG.cpp:1434-1438
+ // For C++ constructor add initializers to CFG. Virtual base classes may have
+ // already been initialized by the superclass. Make a branch so that it was
+ // possible to jump straight to non-virtual bases and fields, skipping
+ // virtual bases. We only need to do this once because all virtual base
+ // initializers go all together before all other initializers.
----------------
Szelethus wrote:
> I find this a little too vague. The standard states:
>
> > First, and only for the constructor of the most derived class (4.5) ,
> > virtual base classes are initialized in the order they appear on a
> > depth-first left-to-right traversal of the directed acyclic graph of base
> > classes, where “left-to-right” is the order of appearance of the base
> > classes in the derived class base-specifier-list.
> >
> > Then, direct base classes are initialized in declaration order as they
> > appear in the (regardless of the order of the mem-initializer s).
> >
> > Then, non-static data members are initialized in the order they were
> > declared in the class definition (again regardless of the order of the
> > mem-initializer s).
> >
> > Finally, the base-specifier-list compound-statement of the constructor body
> > is executed.
>
> This would be an overkill here, but how does this sound like:
>
> > Constructor delegations are ignored to virtual bases unless the object is
> > of the most derived class.
> >
> > class VBase { VBase() = default; VBase(int) {} };
> > class A : virtual public VBase { A() : VBase(0) {} };
> > class B : public A {};
> >
> > B b; // Constructor calls in order: VBase(), A(), B().
> > // VBase(int) is ignored, B isn't the most derived class that
> > // delegates to the virtual base.
> >
> > This may result in the virtual base(s) being already initialized at this
> > point, in which case we should jump right onto non-virtual bases and
> > fields. To handle this, make a CFG branch. We only need to do this once,
> > since the standard states that all virtual bases shall be initialized
> > before non-virtual bases and direct data members.
>
> Also, the comment of mine complementing this inline raises a concern about
> "doing this only once", can you specify?
Mind you, this is the order of initialization for non-delegating constructors!
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D61816/new/
https://reviews.llvm.org/D61816
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