Am 16.01.2016 um 01:29 schrieb Kevin Kofler:
Now, what *I* find "simply *not acceptable*" is that "a seemingly innocuous
piece of code like":
std::vector<Foo> foo1 = …;
std::vector<Foo> foo2 = foo1; // <- here
"leads to a memory allocation, nay, a complete deep copy of the container".
This is particularly problematic when you want to have methods that return
an STL container, because returning a reference is a bad idea. (Of course
you can return a pointer, but that opens its own can of worms, plenty of
ways to shoot yourself in the foot there: the same issues with explicit
sharing semantics as in Java, plus memory leaks and more.)
Almost was going to confirm this example as most relevant use case for
implicit sharing. Sadly, no luckily actually, modern C++ compilers just
optimize this case. The calling method just keeps the callee's instance
alive and reuses it. No constructors involved. Compilers have been smart
enough to do that for a long time. C++11 sanctified that litle trick.
http://stackoverflow.com/questions/4986673/c11-rvalues-and-move-semantics-confusion-return-statement/4986802#4986802
Still in general I agree that time-to-market usually is much more
important like code purity: We are doing products, not religion.
Ciao,
Mathias
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