[Bug c++/43127] Inconsistent and odd constructor calls.

[Bug c++/43127] Inconsistent and odd constructor calls.

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43127

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
First note C++17+ changed the rules so using C++17 allows this to compile,
guaranteed copy elision
(https://en.cppreference.com/w/cpp/language/copy_elision) so no copy is
required or even tried.

Second, the code is in fact invalid C++98/03/11/14 .

To make it valid C++11/14, you can use the rvalue reference instead for the
constructor:
auto_ptr(auto_ptr<type>&& source)

For valid C++98, you could add a constructor which takes a const reference
which allows binding a temporary to it:
auto_ptr(const auto_ptr<type>& source)

[Bug c++/43127] Inconsistent and odd constructor calls.

[stvwooddell at embarqmail dot com]

------- Comment #3 from stvwooddell at embarqmail dot com  2010-02-20 18:13 -------
Scratch that, that's a error from a file that shouldn't even exist. Copied the
given code to a clean project and it compiled. So bug, but a miscommunication
in that the constructor is being implicitly add so that the original form is
trying to pass a anonymous object as a argument to the implicitly added
constructor, which is calling the protected typecast operator.

Still, that leaves the issue that the following has two different behaviours
when they are logically the same. I'm sure this is just a failure on my part to
understand the standard, where is that covered?

ptr Ret(new object(*this));
return Ret;

return Ret(new object(*this));


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43127

[Bug c++/43127] Inconsistent and odd constructor calls.

[stvwooddell at embarqmail dot com]

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------- Comment #2 from stvwooddell at embarqmail dot com  2010-02-20 18:01 -------
This compiles for you?

                virtual ptr clone () const
                {
                        return new object(*this);
                }

gives me the error that a function matching the copy constructor does not
exist:

n file included from ../objects/map.cpp:27:
../objects/../include/object.hpp: In member function ‘virtual auto_ptr<object>
object::clone() const’:
../objects/../include/object.hpp:80: error: no matching function for call to
‘auto_ptr<object>::auto_ptr(auto_ptr<object>)’
../objects/../include/global.hpp:73: note: candidates are:
auto_ptr<type>::auto_ptr(auto_ptr<type>&) [with type = object]
../objects/../include/global.hpp:71: note:                
auto_ptr<type>::auto_ptr(type*) [with type = object]
make: *** [objects/map.o] Error 1

It is my understanding that all the forms should work by creating a (anonymous)
object, then call the copy constructor passing that object as it's only
argument.

In what gcc version or configuration does it work?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43127

[Bug c++/43127] Inconsistent and odd constructor calls.

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2010-02-20 14:00 -------
You can even use

                virtual ptr clone () const
                {
                        return new object(*this);
                }


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43127