Re: Virtual Ctor Idiom and auto_ptr

Alberto Ganesh Barbati <>
29 Nov 2006 18:23:16 -0500
Maxim Yegorushkin ha scritto:

Alberto Ganesh Barbati wrote:


Returning an std::auto_ptr is better than returning a pointer for two


2) it also enforces that, in the sense that the cleanest idiom (i.e.:
hold the result in another auto_ptr) will properly manage custody
automatically, while any other "manual" way of keeping the custody
requires an explicit call to the release() method

Could you post a sample please? The only "manual" thing I could come
with, if I understand you correctly, is the following code, where
release is not necessary:

#include <memory>

int* f() { return new int(); }

int main()
     std::auto_ptr<int> p(new int());
     p.reset(f()); // no release call required

Ehr... this example f() does not *return* an std::auto_ptr... so I don't
understand what is the relationship with what I was saying.

I meant this:

// *returns* an std::auto_ptr
std::auto_ptr<int> f();

void legacy_function_that_takes_custody(int* p);

int main()
   // idiom 1: automatically transfer custody by copying into
   // an std::auto_ptr
   std::auto_ptr<int> a = f();

   // idiom 2: manually obtain custody by explicitly calling release()



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