C++ Memory & Lifetime.

Ownership in C++: RAII, the smart pointers, copies against moves, and the lifetime rules. Covers 12 sub-skills.

• C++ Memory & Lifetime · 1 of 3

  Move Semantics

  A moved-from standard string is measured. What does it report?

  Aa size of oneBa negative sizeCa size of zeroDa size of two

• C++ Memory & Lifetime · 2 of 3

  RAII

  What does this program print for the class holding a raw owning pointer?

  #include <iostream>#include <string>#include <type_traits>struct Five {  std::string* p;  Five() : p(new std::string("x")) {}  ~Five() { delete p; }};int main() {  std::cout << std::boolalpha << std::is_copy_constructible<Five>::value;}

  Acopyable true, which is a trapBcopyable true, which is safeCcopyable false, which is safeDcopyable false, which is a trap

• C++ Memory & Lifetime · 3 of 3

  shared_ptr & weak_ptr

  What does this program print for the holder of itself stored in a member?

  #include <iostream>#include <memory>struct S : std::enable_shared_from_this<S> {  std::shared_ptr<S> self;  void keep() { self = shared_from_this(); }  ~S() { std::cout << "s"; }};int main() {  {    auto s = std::make_shared<S>();    s->keep();  }  std::cout << "|after";}

  Aone mark is printedBtwo marks are printedCno mark is printedDone count is printed