C++ and Beyond

258 Pages·26.515 MB·English

by  Meyers S., Sutter H., Alexandrescu A.

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C++ and Beyond 2010
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Copyright © 2011 Scott Meyers, Herb Sutter, Andrei Alexandrescu.
All rights reserved.
Published March 17, 2011
Produced in the United States of America
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C++ and Beyond
Snoqualmie, Washington, USA
October 24-27, 2010
Schedule
Sunday Monday Tuesday Wednesday
Group Breakfast Group Breakfast Group Breakfast
8:00 - 9:00
[Attic] [Attic] [Attic]
Welcome[Andrei]
Move Semantics, Rvalue A Fresh Look at Containers
Elements of Design, Part 1
9:00 - 10:30 References, and Perfect and Iterators
[Herb]
Forwarding, Part 1 [Andrei]
[Scott]
Break Break Break
Move Semantics, Rvalue
References, and Perfect CAS-Based Concurrency Elements of Design, Part 2
10:45 - 12:00
Forwarding, Part 2 [Andrei] [Herb]
[Scott]
Group Lunch Group Lunch Group Lunch
12:00 - 2:30 and and and
Mid-Day Activity Mid-Day Activity Mid-Day Activity
Super Size Me: Lessons
CPU Caches and
Lambdas, Lambdas, Learned Working at a Web
2:30 - 3:45 Why You Care
Everywhere Company
[Scott]
[Herb] [Andrei]
Break Break
Break
Points and Counterpoints Ask us anything...live!
4:00 - 5:00 Ask us anything...in advance
[Panel] [Panel]
[Panel]
Free Time
5:00 - 7:30
(No Official C&B-Related Activities)
Reception Informal Discussions Informal Discussions
7:30 - 9:30
[Ballroom] [Falls Terrace & Ballroom] [Falls Terrace & Ballroom]
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C++ and Beyond
Snoqualmie, Washington, USA
December 13-16, 2010
Schedule
Monday Tuesday Wednesday Thursday
Group Breakfast Group Breakfast Group Breakfast
8:00 - 8:45
[Attic] [Attic] [Attic]
8:45 - 9:00 Welcome Announcements Announcements
Move Semantics, Rvalue
References, and Perfect Elements of Design, Part 1 Scalable Use of the STL
9:00 - 10:30
Forwarding, Part 1 [Herb] [Andrei]
[Scott]
Break Break Break
Move Semantics, Rvalue
References, and Perfect CAS-Based Concurrency Elements of Design, Part 2
10:45 - 12:00
Forwarding, Part 2 [Andrei] [Herb]
[Scott]
Group Lunch Group Lunch Group Lunch
12:00 - 2:30 and and and
Mid-Day Activity Mid-Day Activity Mid-Day Activity
Super Size Me: Lessons
Lambdas, Lambdas, CPU Caches and
Learned Working at a Web
2:30 - 4:00 Everywhere Why You Care
Company
[Herb] [Scott]
[Andrei]
Break Break Break
Informal C++0x Feature
Q&A Q&A
4:15 - 5:00 Overview
[Andrei, Scott, Herb] [Herb, Andrei, Scott]
[Scott, Herb, Andrei]
Free Time
5:00 - 7:30
(No Official C&B-Related Activities)
Reception Informal Discussions Informal Discussions
7:30 - 9:30
[Falls Terrace] [Falls Terrace] [Falls Terrace]
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Move Semantics, Rvalue References, Perfect Forwarding
Move(cid:2)Semantics,(cid:2)Rvalue(cid:2)References,(cid:2)
and(cid:2)Perfect(cid:2)Forwarding
Scott(cid:2)Meyers,(cid:2)Ph.D.
Software(cid:2)Development(cid:2)Consultant
[email protected] Voice:(cid:2)503/638(cid:3)6028
http://www.aristeia.com/ Fax:(cid:2)503/974(cid:3)1887
Scott(cid:2)Meyers,(cid:2)Software(cid:2)Development(cid:2)Consultant ©(cid:2)2010(cid:2)Scott(cid:2)Meyers,(cid:2)all(cid:2)rights(cid:2)reserved.
http://www.aristeia.com/ Last(cid:2)Revised:(cid:2)12/21/10
C++0x(cid:2)Warning
Some(cid:2)examples(cid:2)show(cid:2)C++0x(cid:2)features(cid:2)unrelated(cid:2)to(cid:2)move(cid:2)semantics.
I’m(cid:2)sorry(cid:2)about(cid:2)that.
But(cid:2)not(cid:2)that(cid:2)sorry(cid:2):(cid:3))
Scott(cid:2)Meyers,(cid:2)Software(cid:2)Development(cid:2)Consultant ©(cid:2)2010(cid:2)Scott(cid:2)Meyers,(cid:2)all(cid:2)rights(cid:2)reserved.
http://www.aristeia.com/ Slide(cid:2)2
Scott Meyers, Software Development Consultant © 2010 Scott Meyers, all rights reserved.
http://www.aristeia.com/
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Move Semantics, Rvalue References, Perfect Forwarding
Move(cid:2)Support
C++(cid:2)sometimes(cid:2)performs(cid:2)unnecessary(cid:2)copying:
typedef std::vector<T> TVec;
TVec createTVec(); // factory function
TVec vt;
…
vt = createTVec(); // copy return value object to vt,
// then destroy return value object
createTVec
vt TVec
T T T … T T T T T T … T T T
Scott(cid:2)Meyers,(cid:2)Software(cid:2)Development(cid:2)Consultant ©(cid:2)2010(cid:2)Scott(cid:2)Meyers,(cid:2)all(cid:2)rights(cid:2)reserved.
http://www.aristeia.com/ Slide(cid:2)3
Move(cid:2)Support
Movingvalues(cid:2)would(cid:2)be(cid:2)cheaper:
TVec vt;
…
vt = createTVec(); // move data in return value object
// to vt, then destroy return value
// object
createTVec
vt TVec
T T T … T T T
Scott(cid:2)Meyers,(cid:2)Software(cid:2)Development(cid:2)Consultant ©(cid:2)2010(cid:2)Scott(cid:2)Meyers,(cid:2)all(cid:2)rights(cid:2)reserved.
http://www.aristeia.com/ Slide(cid:2)4
Scott Meyers, Software Development Consultant © 2010 Scott Meyers, all rights reserved.
http://www.aristeia.com/
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Move Semantics, Rvalue References, Perfect Forwarding
Move(cid:2)Support
Appending(cid:2)to(cid:2)a(cid:2)full(cid:2)vector causes(cid:2)much(cid:2)copying(cid:2)before(cid:2)the(cid:2)append:
std::vector<T> vt;
...
vt.push_back(T object); // assume vt lacks
// unused capacity
vt T T T … T T T
e e e e e e
at at at at at at
St St St St St St
T T T T T T
T T T … T T T T
e e e e e e e
at at at at at at at
St St St St St St St
T T T T T T T
Scott(cid:2)Meyers,(cid:2)Software(cid:2)Development(cid:2)Consultant ©(cid:2)2010(cid:2)Scott(cid:2)Meyers,(cid:2)all(cid:2)rights(cid:2)reserved.
http://www.aristeia.com/ Slide(cid:2)5
Move(cid:2)Support
Again,(cid:2)moving(cid:2)would(cid:2)be(cid:2)more(cid:2)efficient:
std::vector<T> vt;
...
vt.push_back(T object); // assume vt lacks
// unused capacity
vt T T T … T T T
e e e e e e e
at at at at at at at
St St St St St St St
T T T T T T T
T T T … T T T T
Other(cid:2)vector and(cid:2)deque operations(cid:2)could(cid:2)similarly(cid:2)benefit.
(cid:2)
insert,(cid:2)emplace,(cid:2)resize,(cid:2)erase,(cid:2)etc.
Scott(cid:2)Meyers,(cid:2)Software(cid:2)Development(cid:2)Consultant ©(cid:2)2010(cid:2)Scott(cid:2)Meyers,(cid:2)all(cid:2)rights(cid:2)reserved.
http://www.aristeia.com/ Slide(cid:2)6
Scott Meyers, Software Development Consultant © 2010 Scott Meyers, all rights reserved.
http://www.aristeia.com/
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Move Semantics, Rvalue References, Perfect Forwarding
Move(cid:2)Support
Still(cid:2)another(cid:2)example:
template<typename T> // straightforward std::swap impl.
void swap(T& a, T& b)
{
T tmp(a); // copy a to tmp ((cid:3514) 2 copies of a)
a = b; // copy b to a ((cid:3514) 2 copies of b)
b = tmp; // copy tmp to b ((cid:3514) 2 copies of tmp)
} // destroy tmp
a copya ’osf sbt’ast estate
b copyb ’osf sat’ast estate
tmp copy of a’s state
Scott(cid:2)Meyers,(cid:2)Software(cid:2)Development(cid:2)Consultant ©(cid:2)2010(cid:2)Scott(cid:2)Meyers,(cid:2)all(cid:2)rights(cid:2)reserved.
http://www.aristeia.com/ Slide(cid:2)7
Move(cid:2)Support
template<typename T> // straightforward std::swap impl.
void swap(T& a, T& b)
{
T tmp(std::move(a)); // move a’s data to tmp
a = std::move(b); // move b’s data to a
b = std::move(tmp); // move tmp’s data to b
} // destroy (eviscerated) tmp
a a’s state tmp
b b’s state
Scott(cid:2)Meyers,(cid:2)Software(cid:2)Development(cid:2)Consultant ©(cid:2)2010(cid:2)Scott(cid:2)Meyers,(cid:2)all(cid:2)rights(cid:2)reserved.
http://www.aristeia.com/ Slide(cid:2)8
Scott Meyers, Software Development Consultant © 2010 Scott Meyers, all rights reserved.
http://www.aristeia.com/
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Move Semantics, Rvalue References, Perfect Forwarding
Move(cid:2)Support
Moving(cid:2)most(cid:2)important(cid:2)when:
(cid:2)
Object(cid:2)has(cid:2)data(cid:2)in(cid:2)separate(cid:2)memory(cid:2)(e.g.,(cid:2)on(cid:2)heap).
(cid:2)
Copying(cid:2)is(cid:2)deep.
Moving(cid:2)copies(cid:2)only(cid:2)object(cid:2)memory.
(cid:2)
Copying(cid:2)copies(cid:2)object(cid:2)memory(cid:2)+(cid:2)separate(cid:2)memory.
Consider(cid:2)copying/moving(cid:2)A(cid:2)to(cid:2)B:
A copBi ed
A copBied A copBied
c c data Ad daatata
A B
A moBved A moBved
m m data data
Moving(cid:2)never(cid:2)slower(cid:2)than(cid:2)copying,(cid:2)and(cid:2)often(cid:2)faster.
Scott(cid:2)Meyers,(cid:2)Software(cid:2)Development(cid:2)Consultant ©(cid:2)2010(cid:2)Scott(cid:2)Meyers,(cid:2)all(cid:2)rights(cid:2)reserved.
http://www.aristeia.com/ Slide(cid:2)9
Performance(cid:2)Data
Consider(cid:2)these(cid:2)use(cid:2)cases(cid:2)again:
vt = createTVec(); // return/assignment
vt.push_back(T object); // push_back
Copy(cid:3)vs(cid:3)move(cid:2)performance(cid:2)differences(cid:2)notable:
Scott(cid:2)Meyers,(cid:2)Software(cid:2)Development(cid:2)Consultant ©(cid:2)2010(cid:2)Scott(cid:2)Meyers,(cid:2)all(cid:2)rights(cid:2)reserved.
http://www.aristeia.com/ Slide(cid:2)10
Scott Meyers, Software Development Consultant © 2010 Scott Meyers, all rights reserved.
http://www.aristeia.com/
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Move Semantics, Rvalue References, Perfect Forwarding
Move(cid:2)Support
Lets(cid:2)C++(cid:2)recognize(cid:2)move(cid:2)opportunities(cid:2)and(cid:2)take(cid:2)advantage(cid:2)of(cid:2)them.
(cid:2)
How(cid:2)recognize(cid:2)them?
(cid:2)
How(cid:2)take(cid:2)advantage(cid:2)of(cid:2)them?
Scott(cid:2)Meyers,(cid:2)Software(cid:2)Development(cid:2)Consultant ©(cid:2)2010(cid:2)Scott(cid:2)Meyers,(cid:2)all(cid:2)rights(cid:2)reserved.
http://www.aristeia.com/ Slide(cid:2)11
Lvalues(cid:2)and(cid:2)Rvalues
Lvaluesare(cid:2)generally(cid:2)things(cid:2)you(cid:2)can(cid:2)take(cid:2)the(cid:2)address(cid:2)of:
(cid:2)
Named(cid:2)objects.
(cid:2)
Lvalue(cid:2)references.
(cid:2)More(cid:2)on(cid:2)this(cid:2)term(cid:2)in(cid:2)a(cid:2)moment.
Rvaluesare(cid:2)generally(cid:2)things(cid:2)you(cid:2)can’t(cid:2)take(cid:2)the(cid:2)address(cid:2)of.
(cid:2)
Typically(cid:2)unnamed(cid:2)temporary(cid:2)objects.
Examples:
int x, *pInt; // x, pInt, *pInt are lvalues
std::size_t f(std::string str); // str is lvalue, f's return is rvalue
f("Hello"); // temp string created for call
// is rvalue
std::vector<int> vi; // vi is lvalue
…
vi[5] = 0; // vi[5] is lvalue
(cid:2)Recall(cid:2)that(cid:2)vector<T>::operator[] returns(cid:2)T&.
Scott(cid:2)Meyers,(cid:2)Software(cid:2)Development(cid:2)Consultant ©(cid:2)2010(cid:2)Scott(cid:2)Meyers,(cid:2)all(cid:2)rights(cid:2)reserved.
http://www.aristeia.com/ Slide(cid:2)12
Scott Meyers, Software Development Consultant © 2010 Scott Meyers, all rights reserved.
http://www.aristeia.com/
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