Peter Dimov wrote:
Alexander Terekhov wrote:
Maksym Motornyy wrote:
Thanks for articles. Well, I understand that multithreaded environment can be a bad place for COW optimization.
That's a myth.
It depends on the interface of the class. Returning pointers and references into the object is bad, as is const/non-const overloading where the non-const version can be used for read access.
Use const reference/const_cast<> for read access (and non-const object) to avoid unwanted mutations.
Non-const member functions of the begin()/end() variety are worse than just returning a single reference into the object, because you can't "copy on write" between the two, or they'll get out of sync.
Yeah, simply put, mutations of std::string object may invalidate references and iterators (with COW inspired semantics for non- const operator[]() et al. )... threads or no threads, COW or no COW.
Reference-counting immutable objects is fine, but COW can be a pain.
Only in wrong hands. ;-) regards, alexander.