220 29816 <13702f32-32c2-447f-9996-3624fd678675@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: alexandre.isoard@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: New smart pointer: CopyConstructible and CopyAssignable flavor of unique_ptr Date: Fri, 16 Dec 2016 03:32:25 -0800 (PST) Lines: 385 Approved: news@gmane.org Message-ID: <13702f32-32c2-447f-9996-3624fd678675@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_415_597689489.1481887945418" X-Trace: blaine.gmane.org 1481887948 4023 195.159.176.226 (16 Dec 2016 11:32:28 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 16 Dec 2016 11:32:28 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBDXMXE5S7EMRBSVBZ7BAKGQER5XNNMI@isocpp.org Fri Dec 16 12:32:23 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pg0-f72.google.com ([74.125.83.72]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cHqkQ-0000B8-W0 for gclcip-std-proposals@m.gmane.org; Fri, 16 Dec 2016 12:32:23 +0100 Original-Received: by mail-pg0-f72.google.com with SMTP id f188sf177216689pgc.1 for ; Fri, 16 Dec 2016 03:32:27 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:subject:mime-version:x-original-sender :reply-to:precedence:mailing-list:list-id:x-spam-checked-in-group :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=e+t+G0pPVB9sFLLn251wH3470wS3q6AFPoauFGcecUc=; b=xaUOvdsD7LUmFQxFtN/FGMNWrKeH6F9kEfP7qRs7hC6FpJB/VFmWuSBvT40ySqBNjv FyDZG4+u8cASsNIkgeD7zGbbS5nc24NCAsXM3S6byigJUUdxU7y82BZq0GaqqExgz0g3 0fwUOKOK4HTeRA6h6uMqDPDQIFjr4+8Rynv5122Vzhlxptm9XWsCcdPxTTci4dt6Z1LR hcT1+z/mi0OiCOSfVRgZdAvZNfl9AEs+73HA8cEx7gdYf7T1ob4B2ga4h6U+nYVLYGdm qAcS3VmGS7ibOyuAaVsYPO1WsLPxYfyrw/+nzTPfMWvg9sSx01bs3EYQQJ/vPPJ6EF6B ReJg== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:message-id:subject:mime-version:x-original-sender :reply-to:precedence:mailing-list:list-id:x-spam-checked-in-group :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=e+t+G0pPVB9sFLLn251wH3470wS3q6AFPoauFGcecUc=; b=O3FD3bfgr06Bhr99Ruokm5y+c/NFTPOGIeylyCP9dbJlmlp1fUYhZ3ITrQhUwISCII ucvt78f632Z/FkG+EOgUrC2FfiSuvb7gS3lTrLdzovp9EZBkVD5um5BW8bQaMJcPjI0I rs2+hR+9Kdkr/tj7rgRG6oRd8puj0SedqTd6E7qHi4Y9sVjQUsyKdTPvH1geeZnY/syc 43+2eB2OcavN8B+Ov2M3uObDIfoMpnNBFrhj/2+EqqzqzD/ff4ek9Fw7nueObbqkv0Cj KVYRafIsMt/JBbpSsLZNACFy8p1G4NLIebYVfxW0NPxvS8BAIteMoSVH5NGDZh+3dR1G QaEA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:message-id:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=e+t+G0pPVB9sFLLn251wH3470wS3q6AFPoauFGcecUc=; b=hKBE43CUGAThChvuEVUg7ccmHG/HoJlNQTUmt7Hff9o12rcBDzP0BnEg1tFYCq50S4 bGz4bQB890w/8NJ7+Di1HR8/jyK5b2wI6Z220/TQnbMPVoMyNyrEKNIzMyorG5Xgxp4k dAIafFQSXeS4BpVV+BgnsPRf3EgoFrZVc44HsykNvPOUXKPGM+bSbqzfbFJB3f0a3O6t bwAkU6mVlSdoH4udKMRM08XD0PYi/ZZHVf1ebu5SQbeeck4xML4ymTVHg+8URSXJ/Kd3 v9wPPKH8OTwex41SkuthrdcR7kaNx/L7OJBj2xxpisRBLtuH1Sz3DTfy/IhQ9nsaT+qB UP/w== X-Gm-Message-State: AKaTC03QxzcCAXKRsADd9WmHrW8aHT0QRYUR7k41kM5H6J4pect/shP2oBah6Pw+F7b8Ag== X-Received: by 10.99.56.69 with SMTP id h5mr1072130pgn.113.1481887946772; Fri, 16 Dec 2016 03:32:26 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.41.209 with SMTP id g17ls8337664otd.46.gmail; Fri, 16 Dec 2016 03:32:25 -0800 (PST) X-Received: by 10.157.20.197 with SMTP id r5mr85866otr.9.1481887945888; Fri, 16 Dec 2016 03:32:25 -0800 (PST) X-Original-Sender: alexandre.isoard@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:29816 Archived-At: ------=_Part_415_597689489.1481887945418 Content-Type: multipart/alternative; boundary="----=_Part_416_1112300632.1481887945419" ------=_Part_416_1112300632.1481887945419 Content-Type: text/plain; charset=UTF-8 *Proposal* template, class Deleter = std::default_delete > class copy_ptr std::copy_ptr is a smart pointer that owns and manages another object through a pointer and disposes of that object when the copy_ptr goes out of scope. Additionally, it allocates a clone of the underlying object when it is copied from, ensuring one copy_ptr manages each allocated object. The object is disposed of using the associated deleter when either of the following happens: - the managing copy_ptr object is destroyed - the managing copy_ptr object is assigned another pointer via operator= or reset() . The object is disposed of using a potentially user-supplied deleter by calling get_deleter()(ptr). The default deleter uses the delete operator, which destroys the object and deallocates the memory. The object is cloned using the associated cloner when either of the following happens: - an other copy_ptr object is copy constructed from the managing copy_ptr - an other copy_ptr object is copy assigned from the managing copy_ptr The object is cloned using a potentially user-supplied cloner by calling get_cloner()(ptr). The default cloner uses the new operator and the copy constructor of the underlying type, which allocate a new object and copy its original content. A copy_ptr may alternatively own no object, in which case it is called empty. The class satisfies the requirements of MoveConstructible , MoveAssignable , CopyConstructible and CopyAssignable (the later two may require T to be CopyConstructible). *Member Types* - pointer: T* - element_type: T, the type of the object managed by this copy_ptr - cloner_type: Cloner, the function object or lvalue reference to function or to function object, to be called from the copy constructor and copy assignment operators - deleter_type: Deleter, the function object or lvalue reference to function or to function object, to be called from the destructor *Member Functions* - operator=: assigns the copy_ptr - release: returns a pointer to the managed object and releases ownership - reset: replaces the managed object - swap: swaps the managed objects - get: returns a pointer to the managed object - get_cloner: returns the cloner that is used for copy the managed object - get_deleter: returns the deleter that is used for destruction of the managed object - operator bool: checks if there is an associated managed object - operator*, operator->: dereferences pointer to the managed object - make_copy: creates a copy pointer that manages a new object - operator==, operator!=, etc: compares to an other copy_ptr or with nullptr - std::swap: specializes the std::swap algorithm - std::hash: hash support for std::copy_ptr *Example* #include #include struct Foo { Foo() { std::cout << "Foo::Foo()\n"; } Foo(const Foo& o) { std::cout << "Foo::Foo(const Foo&)\n"; } ~Foo() { std::cout << "Foo::~Foo()\n"; } void bar() { std::cout << "Foo::bar()\n"; } } void f(const Foo&) { std::cout << "f(const Foo&)\n"; } int main() { std::copy_ptr p1(new Foo); // p1 owns Foo if (p1) p1->bar(); { std::copy_ptr p2(std::move(p1)); // now p2 owns Foo f(*p2); p1 = p2; // cloned into p1 std::cout << "destroying p2...\n"; } if (p1) p1->bar(); // Second Foo instance is destroyed when p1 goes out of scope } Output: Foo::Foo() Foo::bar() f(const Foo&) Foo::Foo(const Foo&) destroying p2... Foo::~Foo() Foo::bar() Foo::~Foo() -- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/13702f32-32c2-447f-9996-3624fd678675%40isocpp.org. ------=_Part_416_1112300632.1481887945419 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Proposal

template<class T,
=C2=A0 =C2=A0 class Cloner =3D std::default_clone<T>,
=C2=A0 =C2=A0 class Deleter =3D std::default_delete<T>
> class copy_ptr

std::copy_ptr is a smart pointer that owns and manages a= nother object through a pointer and disposes of that object when the copy_ptr goes out of scope.
Addi= tionally, it allocates a clone of the underlying object when it is copied f= rom, ensuring one copy_ptr man= ages each allocated object.

The object is disposed of using the asso= ciated deleter when either of the following happens:
  • the managin= g copy_ptr object is destroyed=
  • the managing copy_ptr object is assigned another pointer via operator=3D or reset().
    • <= /ul>The object is disposed of using a potentially user-supplied deleter by = calling get_deleter()(ptr). Th= e default deleter uses the delete operator, which destroys the object and deallocates the memory.

The object is cloned using the associated cloner when eit= her of the following happens:
  • an other copy_ptr object is copy constructed from the man= aging copy_ptr
  • an other copy_= ptr object is copy assigned from the managing copy_ptr
The object is cloned using a potentially user-supplied cloner by calling <= font face=3D"courier new, monospace">get_cloner()(ptr). The default = cloner uses the new operator a= nd the copy constructor of the underlying type, which allocate a new object= and copy its original content.

A copy_ptr may alternatively own no object, in which case it is = called empty.

The class satisfies the requirements of MoveConstru= ctible,=C2=A0MoveAssignable, CopyConstructible and=C2=A0CopyAssignable=C2=A0(= the later two may require T to be CopyConstructible).

Member Types
  • pointer: T*
  • element_type: T, the type of the object managed by thi= s copy_ptr
  • cloner_type:=C2=A0Cloner, the function object or lvalue reference to f= unction or to function object, to be called from the copy constructor and c= opy assignment operators
  • dele= ter_type:=C2=A0Deleter,= the function object or lvalue reference to function or to function object,= to be called from the destructor

Mem= ber Functions
  • operator=3D: assigns the copy_ptr
    • <= li>release: returns a pointer to the managed object and releases ownership<= /li>
  • reset: replaces the managed object
  • swap: swaps the managed = objects
  • get: returns a pointer to the managed object
  • get_cl= oner: returns the cloner that is used for copy the managed object
  • g= et_deleter: returns the deleter that is used for destruction of the managed= object
  • operator bool: checks if there is an associated managed obj= ect
  • operator*, operator->: dereferences pointer to the managed o= bject
  • make_copy: creates a copy pointer that manages a new object
  • operator=3D=3D, operator!=3D, etc: compares to an other copy_ptr or = with nullptr
  • std::swap: specializes the std::swap algorithm
    • std::hash<std::copy_ptr>: hash support for std::copy_ptr
Example

#include<iostream>=
#include<= span style=3D"color: #080;" class=3D"styled-by-prettify"><memory>

struct Foo
{
=C2=A0 =C2=A0 Foo() =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 { std::cout << "Foo::Foo()\n"; }
=C2=A0 =C2=A0 Foo(const<= /span> Foo& o) { std::cout <= /span><< "Foo::Foo(const F= oo&)\n"; }
=C2=A0 =C2=A0 ~Foo() =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0{ std::cout << "Foo::~Foo()\n"; }
=C2=A0 =C2=A0 void bar() =C2=A0 =C2=A0 =C2=A0 =C2=A0{ std::cout = << <= /span>"Foo::= bar()\n"; }
}

void f(const Foo&)=
{
=C2=A0 =C2=A0 std::cout << "f(const Foo&)\n";
}

int main()
{
=C2=A0 =C2=A0 std::copy_ptr<Foo> p1(new Foo); = =C2=A0// p1 owns Foo
=C2=A0 =C2=A0 if (p= 1) p1->bar();
=C2=A0
=C2=A0 =C2=A0 {
=C2= =A0 =C2=A0 =C2=A0 =C2=A0 std::copy_ptr<Foo> p2(std::move(p1)); =C2=A0= // now p2 owns Foo
=C2=A0 =C2=A0 =C2=A0 = =C2=A0 f(*p2);
=C2=A0
=C2=A0 =C2=A0 =C2=A0 =C2=A0 p1 =3D p2; =C2=A0// cloned int= o p1
=C2=A0 =C2=A0 =C2=A0 =C2=A0 std::co= ut << "destroying p2...\n";
=C2=A0 =C2=A0 }
=C2=A0
=C2=A0 =C2=A0 if (p1) p1->bar();
=C2=A0
=C2=A0 =C2=A0= // Second Foo instance is destroyed when p1 goes out of scope
= }

Output:

Foo::Foo()
Foo::bar(= )
f(const Foo&)<= /font>
Foo::Foo(const Foo&a= mp;)
destroying p2..= ..
Foo::~Foo()=
Foo::bar()
Foo::~Foo()

--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+unsubscribe@isocpp.org.
To post to this group, send email to std-proposals@isocpp.org.
To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/13702f32-32c2-447f-9996-3624fd678675= %40isocpp.org.
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