Re: Class with functions that return STL containers with incomplete types

"Victor Bazarov" <>
Wed, 9 Jan 2008 15:45:47 -0500
Joe Greer wrote:

massysett <> wrote in


Having classes with member objects that have STL containers of
objects whose definitions are incomplete results in undefined
behavior. See for example:
39 .14

I am wondering: is it okay to have member functions that return an
STL container with an incomplete type? My member objects do not
contain incomplete types. For instance, would the following code be
OK? Thanks. --Omari

#include <boost/shared_ptr.hpp>
#include <vector>

class HasSelf
    HasSelf(std::vector<HasSelf>& contents);
    std::vector<HasSelf> getContents() const;

    std::vector<boost::shared_ptr<HasSelf> > _contents;

shared_ptr<> does not require that the class be complete, but in this
case, shared_ptr itself is complete. Therefore you can have a vector
of shared_ptrs to an incomplete class. I assume that since the
member is a vector of shared_ptrs, that the other vectors are also
vectors of shared_ptrs?

That would require at least creating them using some kind of memory
management (like 'new'), which is more expensive and less efficient
than letting a 'vector' handle the entire array of those. Of course,
if legality is the primary concern, it seems like the only viable

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