----- Original Message ----
From: Sergiu Dotenco <sergiu.dotenco@gmail.com>
Am 26.05.2011 18:28, schrieb Artyom Beilis:
From: Sergiu Dotenco <sergiu.dotenco@gmail.com>
Am 26.05.2011 11:22, schrieb Artyom Beilis:
The only advantage I can see in boost.pimpl over scoped_ptr or auto_ptr is that it does not require explicit destructor.
i.e.
class Foo : boost::noncopyable { public: Foo(); int x() const; void x(int v); private: struct data; std::auto_ptr<data> d; };
No good. You need to add
~Foo();
So it would know to destroy Foo::Data correctly.
You can't use std::auto_ptr for pimpl implementation in portable code. Doing so is undefined behavior. To quote ISO/IEC 14882:2003 (§17.4.3.6, p. 329):
"In particular, the effects are undefined in the following cases: [...] — if an incomplete type (3.9) is used as a template argument when instantiating a template component, unless specifically allowed for that component."
which applies to most standard library types.
When you actually implement Foo::~Foo() {} in cpp file the type of the data object is complete so the destructor is installed correctly.
That's not correct. std::auto_ptr<data> is an instantiation which uses an incomplete type as template argument. Providing an non-inline destructor doesn't magically make the data struct used in your example a complete type.
The quote you provide is too general about the library requirements. Particularly, looking into auto_ptr. (20.4.5.1 C++/2003 standard) ~auto_ptr() throw(); Requires: The expression delete get() is well formed. Effects: delete get(). The expression delete get() is well formed when ~auto_ptr() is called in the destructor of Foo::~Foo() defined in cpp file. So it fills auto_ptr requirements. No problems I can see also I'm not aware of any compiler that does not handle this correctly (so far Intel, GCC, MSVC, SunStudio, HP's ACC, DECXX) Artyom