[](){}(); C++11 as a new language Thiago Macieira OSCON 2012 Who - - PowerPoint PPT Presentation

[](){}(); C++11 as a new language

Thiago Macieira OSCON 2012

INTEL CONFIDENTIAL 2

Who am I?

• Open Source developer for over 15 years

Developing with C++ since 2000

• Working for Intel’s Open Source Technology Center
• Maintainer of modules in the Qt* open source project
• MBA and double degree in Engineering
• Collect way too many air miles presenting in events

* Other names and brands may be claimed as property of others

INTEL CONFIDENTIAL 3

Status of C++11

• Approved by ISO on August 2011
• Published as ISO/IEC 14882:2011
• Partial support in most compilers
• Portions of it incorporated into

ISO/IEC 9899:2011 – that is, C11

Native matters

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INTEL CONFIDENTIAL 5

C and C++ are very widespread

• Operating systems
• Middleware layers
• High-end games

C++

PHP WebKit Gecko V8

C

Python Ruby JRE’s JVM

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Native development still crucial

• Performance, performance, performance

– “Bare metal”, no compromises

• Accessing devices
• Resource-limited

environments

C C++ Java 7 JavaScript V8 Ruby 1.9 PHP Python 3 1 10 100 1000 Source: “The Computer Language Benchmarks Game”, http://shootout.alioth.debian.org/

Multiples of fastest program

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Also reflected in the job market

Source: indeed.com

• Maintenance
• New development

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Will continue expanding

• User interfaces getting more complex
• Embedded market growing
• Existing installations requiring maintenance and

improvements Arm wrestling between hardware and UX requirements

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Why change?

• What’s wrong with C99 and C++98?

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C++11 goals

• Evolve the language
• Keep compatibility with C++98 and C
• Prioritise library and system design
• Improve type-safety techniques
• Improve concurrency / threading support

New features

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What’s new in C++11?

Rvalue references Move semantics constexpr Trivial types Standard layout types Extern templates Initialiser lists Uniform initialisation auto types decltype Range-based for Lambdas Delegating constructors Inheriting constructors Explicit overrides nullptr enum class Template alias Unrestricted unions Variadic templates Unicode strings User-defined literals Memory model Defaulted & deleted members Static assertions alignof and alignas Atomic types std::tuple std::regex std::shared_ptr std::function Type traits Raw strings thread_local >>

Entries in bold are also in C11

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Atomics and memory model

• Improving support for multi-threaded programs:

– No more poorly-defined “sequence points” in the standard – The standard now talks about “happens before” – Low-level atomic operations library

• Both features in C11 too
• Lock-free programming without assembly

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constexpr

template<int N> struct Factorial { enum { Result = N * Factorial<N - 1>::Result }; }; template<> struct Factorial<0> { enum { Result = 1 }; }; char array1[Factorial<4>::Result]; constexpr int factorial(int n) { return n == 0 ? 1 : n * factorial(n - 1); } char array2[factorial(4)];

• Under strict rules, allows the compiler to “run” the code
• A new way of meta-programming

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Lambdas

• First-class citizens in C++11
• Improves readability by keeping code close by.
• Syntax:

auto f = [captures go here](parameters go here) { code goes here } – Special captures: = captures the entire scope by value & captures the entire scope by reference

INTEL CONFIDENTIAL 16

Modern strings

• This is 2012, we have Unicode:

const char16_t greek[] = u"Γεια σου, κόσμε!"; const char32_t russian[] = U"Здравствуй, мир!";

• Criticism: no standard marker for source code encoding

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Compiler support for C++11

• GCC 4.7: best support

http://gcc.gnu.org/projects/cxx0x.html

• Clang 3.1: like GCC

http://clang.llvm.org/cxx_status.html

• Intel CC 12.1: decent support

http://software.intel.com/en-us/articles/c0x-features-supported-by-intel-c-compiler

• Microsoft Visual Studio 2010: lagging behind

(situation improves with 2012)

• More information: http://wiki.apache.org/stdcxx/C++0xCompilerSupport

Go beyond

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INTEL CONFIDENTIAL 19

Example: threading

High-level:

• Cross-platform API for

threads and mutexes

• Known behaviour
• No third-party frameworks

Low-level:

• Lock-free programming
• Memory model makes it clear

what can or can’t happen

– Compiler optimisations

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Example: type traits

• New type definitions:

– Standard layout – Trivial

• Allows generic containers to optimise operations
• memcpy & realloc

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Example: type traits & move semantics

• New type definitions:

– Standard layout – Trivial

• Huge library of traits, like

– is_enum, is_function, is_pod – is_polymorphic, is_abstract – is_nothrow_constructible, has_virtual_destructor

• “Temporaries” can be

modified

• Avoids copying unnecessarily

More efficient containers

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Why this is important for open source?

• Fewer occasions for

undefined behaviour

• Incremental improvements

for existing code More readable code Better code Fewer bugs Happy users!

INTEL CONFIDENTIAL 23

Thank you

• Questions?
• This presentation will be available at:

http://oscon.com/slides

• thiago.macieira@intel.com