220 29861 <731cb931-eb89-41e0-8c1b-bfccd6329eaa@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: jgottman6@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: New smart pointer: CopyConstructible and CopyAssignable flavor of unique_ptr Date: Fri, 16 Dec 2016 18:45:38 -0800 (PST) Lines: 421 Approved: news@gmane.org Message-ID: <731cb931-eb89-41e0-8c1b-bfccd6329eaa@isocpp.org> References: <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_349_817252494.1481942738584" X-Trace: blaine.gmane.org 1481942745 12761 195.159.176.226 (17 Dec 2016 02:45:45 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sat, 17 Dec 2016 02:45:45 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBD7LHGWIQEPRBU6N2LBAKGQEJ6IPLVQ@isocpp.org Sat Dec 17 03:45:40 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pg0-f69.google.com ([74.125.83.69]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cI50C-0001ox-A7 for gclcip-std-proposals@m.gmane.org; Sat, 17 Dec 2016 03:45:37 +0100 Original-Received: by mail-pg0-f69.google.com with SMTP id 3sf233099331pgd.3 for ; Fri, 16 Dec 2016 18:45:40 -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:in-reply-to:references: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=zg0E8VH7RmoqRJsO7qiuScB3WQxppz3ISNlwF3Nb6WU=; b=cK7RCAIt4ZV2a6zT6lQf3I7hMjPEve59FQGF1EiwtwVKASUNXNpKPfidRUIIcVicuq DSF7vy35ndyeHEpgiQ9ELOJEKA7Uw2bLQ9j1xd5HwwFRblQ6xMhsqaYh6xkE4xwHjp+w k4uDfH4XBWPA7YvggLZdM3mt9ea4hDzx7RvkuQYcGdhubsIWUBsMlYOFtnANxpVj0asA ICy8Yjtl0eQSPCa87iudzxSNh+fM/f5taHtk6e+WzfXTVYP+U7YSaoxD3IA/X3cPzNKp hFgujtFCjMT4y3cXSLkhLBX4XdP/g9TnPG8I39CS+ztlU7CouJkkKiQYv8gwgxNBitQo MF1A== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:message-id:in-reply-to:references: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=zg0E8VH7RmoqRJsO7qiuScB3WQxppz3ISNlwF3Nb6WU=; b=Bz5bl/Ll5KUhgraV7yZcjuBwBNT2hcRX7KjY7JmN4hwilJYl7IWlV6i7M1mq5wvIX9 PQJWI9Ocjsha04YIgs1qF+blnc4/qKX2lh9Ufam7c54mN7izx1u+kt6H95upCFJ30CgB zOPJlCvqvroWTXcQR6acuvDrN8fI22WPYVENwx288jPyNvO6apErHa5QcrxdToCKRSZc lONZltpoOKYWDiqZaw6mFN465ct2P62r0vFWQCvHh1Jw8W3GkQDuOPM/aG5o7Bto/qBW GtyG/YGI4VICcE31s2oTQEORoO5mq8Y3bTFrS9VNUUwF+X40Jp0Uhev1QpVNajr/QY7V lJHQ== 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:in-reply-to:references :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=zg0E8VH7RmoqRJsO7qiuScB3WQxppz3ISNlwF3Nb6WU=; b=Hmy3RJ8E5ClnnnP0mhnI9zZWrKkx/79Zas/ftOZx3vr2YFE9Fx36VD2VsGSW8CO0m8 TCq0OPvzq3YXiLvN+koh4dDgNrdoyon154zW27mcfOYxPp2iHG2Cjjgm6g6GWJOr5m9b etht9zhAg9DDLii7f/STgtEEP9doi0nyJwTr8SsjX0+zCVEmWvyODhbPy9drCRcOmAo4 P9FxIjFpOTzAeFV+mnDQZuQm2RAB+TudjkegABoWZ2p1OVH9yu5M/bwNn426aURmqeoe mEmJ1mo/13rtDF9p6jbSLp5k2hMgFX80WWXmfsC9tPgNFTptIUcMel+xDtHa0zYPNp8d orxQ== X-Gm-Message-State: AKaTC03U++DoklpClOtGcnCxQKw/fg3GROfkJX3X9xRBaT6fDM6cbGw6c7xcx82WV42rZQ== X-Received: by 10.99.124.13 with SMTP id x13mr2888203pgc.97.1481942739885; Fri, 16 Dec 2016 18:45:39 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.43.168 with SMTP id u37ls1983496ota.29.gmail; Fri, 16 Dec 2016 18:45:39 -0800 (PST) X-Received: by 10.157.45.49 with SMTP id v46mr283594ota.10.1481942739124; Fri, 16 Dec 2016 18:45:39 -0800 (PST) In-Reply-To: <13702f32-32c2-447f-9996-3624fd678675@isocpp.org> X-Original-Sender: jgottman6@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:29861 Archived-At: ------=_Part_349_817252494.1481942738584 Content-Type: multipart/alternative; boundary="----=_Part_350_483177092.1481942738585" ------=_Part_350_483177092.1481942738585 Content-Type: text/plain; charset=UTF-8 Please don't define any relational operators for this class. If the relational operators are defined to compare the contained pointers, then given the code clone_ptr foo(new int(7)); clone_ptr bar = foo; assert(foo == bar); the assertion will fail. This means that code using clone_ptr's in associative containers will compile but completely fail to work at runtime. Joe Gottman On Friday, December 16, 2016 at 6:32:25 AM UTC-5, Alexandre Isoard wrote: > > *Proposal* > > template class Cloner = std::default_clone, > 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/731cb931-eb89-41e0-8c1b-bfccd6329eaa%40isocpp.org. ------=_Part_350_483177092.1481942738585 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Please don't define any relational operators for this = class. If the relational operators are defined to compare the contained poi= nters, then given the code

clone_ptr<int> foo(new int(7));
clone_ptr<int> bar =3D foo;
assert(fo= o =3D=3D bar<= span style=3D"color: #660;" class=3D"styled-by-prettify">);


the assertion will fail.=C2=A0 This means that code using= clone_ptr's in associative containers will compile but completely fail= to work at runtime.

Joe Gottman


On Friday, December 16, = 2016 at 6:32:25 AM UTC-5, Alexandre Isoard wrote:
Proposal

template<class T,
=C2=A0 =C2=A0 <= /span>class Cloner =3D std::default= _clone<T>,
=C2=A0 =C2=A0 class Deleter =3D std<= span style=3D"color:#660">::default_delet= e<T>=
> class= copy_ptr

copy_ptr goes out of scope.
Additionally, = it allocates a clone of the underlying object when it is copied from, ensur= ing one copy_ptr manages each = allocated object.

The object is disposed of using the associated del= eter when either of the following happens:
  • the managing copy_ptr object is destroyed
    • <= li>the managing copy_ptr objec= t is assigned another pointer via operator=3D or reset().
The obj= ect is disposed of using a potentially user-supplied deleter by calling get_deleter()(ptr). The default d= eleter uses the delete operato= r, 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 us= es the new operator and the co= py constructor of the underlying type, which allocate a new object and copy= its original content.

A cop= y_ptr may alternatively own no object, in which case it is called em= pty.

The class satisfies the requirements of MoveConstructible,=C2=A0MoveAssignable, CopyConstructible and=C2=A0pointer: T*
  • elem= ent_type: T, the type o= f the object managed by this copy_ptr=
  • cloner_type:= =C2=A0Cloner, the function obj= ect or lvalue reference to function or to function object, to be called fro= m the copy constructor and copy assignment operators
  • deleter_type:=C2=A0Deleter, the function object or lvalue reference to fun= ction or to function object, to be called from the destructor

    • Member Functions
    • operator=3D= : assigns the copy_ptr
    • release: returns a pointer to the managed ob= ject and releases ownership
    • reset: replaces the managed object
      • =
    • swap: swaps the managed objects
    • get: returns a pointer to the m= anaged object
    • get_cloner: returns the cloner that is used for copy = the managed object
    • get_deleter: returns the deleter that is used fo= r destruction of the managed object
    • operator bool: checks if there = is an associated managed object
    • operator*, operator->: dereferen= ces pointer to the managed object
    • make_copy: creates a copy pointer= that manages a new object
    • operator=3D=3D, operator!=3D, etc: compa= res to an other copy_ptr or with nullptr
    • std::swap: specializes the= std::swap algorithm
    • std::hash<std::copy_ptr>: hash support f= or std::copy_ptr
    Example

    <= font color=3D"#660066">#include<iostream>
    #include<= ;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 Foo& o) { std::cout << "Foo::Foo(const Foo&)\= n"; }
    = =C2=A0 =C2=A0     ~Foo() =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0{ std::cout << "Foo::~Foo()\n";<= span style=3D"color:#000"> }
    =C2=A0 =C2=A0     vo= id bar(= ) =C2=A0 =C2=A0 =C2=A0 =C2=A0{ std::cout << "Foo::bar()\n"; = }
    }<= /span>

    = void f(= const <= /span>Foo&= )
    {<= /span>
    =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 ow= ns Foo
    =C2=A0 =C2=A0 if (p1) 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 into p1
    =C2=A0 =C2=A0 =C2=A0 = =C2=A0 std::cout << "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 w= hen 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 &= 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/731cb931-eb89-41e0-8c1b-bfccd6329eaa= %40isocpp.org.
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