What type should C++ object creation functions return (e.g. pointer, smart
pointer, reference, etc.)? Several of our C++ API's return shared
pointers. For example in the following function signature [1]:
std::shared_ptr<CacheFactory> CacheFactory::createCacheFactory(...);
Here the only case I can see for shared pointer is to indicate ownership of
CacheFactory. Ideally this should probably be std::unique_ptr because
callee shouldn't share ownership. However, I don't see the point of using
a pointer at all.. I suggest we return the bare object, like the following
signature:
CacheFactory CacheFactory::createCacheFactory(...);
In C++03, this would have been a performance hit because we'd end up with
an added call to the copy constructor. In C++11, std::unique_ptr gives
std::move for free and thus avoids copy-constructor call. However, most
modern C++11 compilers already perform copy-elision here. In fact, C++17
standard dictates that compilers must perform RVO here. Therefore it
doesn't seem to me that std::shared_ptr or std::unique_ptr buys us much in
this situation.
Thoughts?
Thanks,
David
[1] https://github.com/apache/geode-native/blob/develop/
cppcache/include/geode/CacheFactory.hpp#L54
