std::auto_ptr to std::unique_ptr

Question

With the new standard coming (and parts already available in some compilers), the new type std::unique_ptr is supposed to be a replacement for std::auto_p

Answer 1

std::auto_ptr and std::unique_ptr are incompatible in someways and a drop in replacement in others. So, no find/replace isn't good enough. However, after a find/replace working through the compile errors should fix everything except weird corner cases. Most of the compile errors will require adding a std::move.

• Function scope variable:
  100% compatible, as long as you don't pass it by value to another function.
• Return type:
  not 100% compatible but 99% compatible doesn't seem wrong.
• Function parameter by value:
  100% compatible with one caveat, unique_ptrs must be passed through a std::move call. This one is simple as the compiler will complain if you don't get it right.
• Function parameter by reference:
  100% compatible.
• Class member variable:
  This one is tricky. std::auto_ptrs copy semantics are evil. If the class disallows copying then std::unique_ptr is a drop in replacement. However, if you tried to give the class reasonable copy semantics, you'll need to change the std::auto_ptr handling code. This is simple as the compiler will complain if you don't get it right. If you allowed copying of a class with a std::auto_ptr member without any special code, then shame on you and good luck.

In summary, std::unique_ptr is an unbroken std::auto_ptr. It disallows at compile time behaviors that were often errors when using a std::auto_ptr. So if you used std::auto_ptr with the care it needed, switching to std::unique_ptr should be simple. If you relied on std::auto_ptr's odd behavior, then you need to refactor your code anyway.