| <!DOCTYPE html> |
| <!-- |
| Copyright 2014 The Chromium Authors. All rights reserved. |
| Use of this source code is governed by a BSD-style license that can be |
| found in the LICENSE file. |
| --> |
| <html> |
| <head> |
| <meta charset="utf-8"> |
| <title>C++11 use in Chromium</title> |
| <link rel="stylesheet" href="c++11.css"> |
| <style> |
| table tbody tr td:first-child { |
| font-weight: bold; |
| font-size: 110%; |
| } |
| </style> |
| </head> |
| <body> |
| <div id="content"> |
| <h1>C++11 use in Chromium</h1> |
| |
| <p><i>This document lives at src/styleguide/c++/c++11.html in a Chromium |
| checkout.</i></p> |
| |
| <p>This document summarizes the features of C++11 (both in the language itself |
| and in enhancements to the Standard Library) and describes which features are |
| allowed in Chromium and contains pointers to more detailed information. The |
| Guide applies to Chromium and its subprojects. Subprojects can choose to be |
| more restrictive if they need to compile on more toolchains than Chromium.</p> |
| |
| <p>You can propose to make a feature available or to ban a |
| feature by sending an email to <a |
| href="https://groups.google.com/a/chromium.org/forum/#!forum/cxx">cxx@chromium.org</a>. |
| Ideally include a short blurb on what the feature is, and why you think it |
| should or should not be allowed. Ideally, the list will arrive at some |
| consensus and the wiki page will be updated to mention that consensus. If |
| there's no consensus, <code>src/styleguide/c++/OWNERS</code> get to decide -- |
| for divisive features, we expect the decision to be to not use the feature yet |
| and possibly discuss it again a few months later, when we have more experience |
| with the language.</p> |
| |
| <h2>Table of Contents</h2> |
| <ol class="toc"> |
| <li>Allowed Features<ol> |
| <li><a href="#core-whitelist">Language</a></li> |
| <li><a href="#library-whitelist">Library</a></li> |
| </ol></li> |
| <li>Banned Features<ol> |
| <li><a href="#core-blacklist">Language</a></li> |
| <li><a href="#library-blacklist">Library</a></li> |
| </ol></li> |
| <li>To Be Discussed<ol> |
| <li><a href="#core-review">Language</a></li> |
| <li><a href="#library-review">Library</a></li> |
| </ol></li> |
| </ol> |
| |
| <h2 id="whitelist"><a name="core-whitelist"></a>C++11 Allowed Features</h2> |
| |
| <p>The following features are currently allowed.</p> |
| |
| <table id="whitelist_lang_list" class="unlined striped"> |
| <tbody> |
| |
| <tr> |
| <th style='width:220px;'>Feature</th> |
| <th style='width:260px;'>Snippet</th> |
| <th style='width:240px;'>Description</th> |
| <th style='width:240px;'>Documentation Link</th> |
| <th style='width:240px;'>Notes and Discussion Thread</th> |
| </tr> |
| |
| <tr> |
| <td>Aliases</td> |
| <td><code>using <i>new_alias</i> = <i>typename</i></code></td> |
| <td>Allow parameterized typedefs</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/type_alias">Type alias (using syntax)</a></td> |
| <td>Use instead of typedef, unless the header needs to be compatible with C. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/8dOAMzgR4ao">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Angle Bracket Parsing in Templates</td> |
| <td><code>>></code> for <code>> ></code>, <code><::</code> for <code>< ::</code></td> |
| <td>More intuitive parsing of template parameters</td> |
| <td><a href="http://stackoverflow.com/questions/15785496/c-templates-angle-brackets-pitfall-what-is-the-c11-fix">C++ Templates Angle Brackets Pitfall</a></td> |
| <td>Recommended to increase readability. Approved without discussion.</td> |
| </tr> |
| |
| <tr> |
| <td>Arrays</td> |
| <td><code>std::array</code></td> |
| <td>A fixed-size replacement for built-in arrays, with STL support</td> |
| <td><a href="http://en.cppreference.com/w/cpp/container/array">std::array</a></td> |
| <td>Useful in performance-critical situations, with small, fixed-size arrays. In most cases, consider std::vector instead. std::vector is cheaper to std::move and is more widely used. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/cxx/pVRQCRWHEU8">Discussion thread</a>.</td> |
| </tr> |
| |
| <tr> |
| <td>Automatic Types</td> |
| <td><code>auto</code></td> |
| <td>Automatic type deduction</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/auto">auto specifier</a></td> |
| <td><a href="https://google.github.io/styleguide/cppguide.html#auto">Google Style Guide</a>. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/OQyYSfH9m2M">Discussion thread</a>. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/5-Bt3BJzAo0">Another discussion thread</a>.</td> |
| </tr> |
| |
| <tr> |
| <td>Constant Expressions</td> |
| <td><code>constexpr</code></td> |
| <td>Compile-time constant expressions</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/constexpr">constexpr specifier</a></td> |
| <td>Prefer to <code>const</code> for variables where possible. Use cautiously on functions. Don't go out of the way to convert existing code. <a href="https://google.github.io/styleguide/cppguide.html#Use_of_constexpr">Google Style Guide</a></td> |
| </tr> |
| |
| <tr> |
| <td>Declared Type Accessor</td> |
| <td><code>decltype(<i>expression</i>)</code></td> |
| <td>Provides a means to determine the type of an expression at compile-time, useful most often in templates.</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/decltype">decltype specifier</a></td> |
| <td>Usage should be rare. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/_zoNvZd_dSo">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Default Function Creation</td> |
| <td><code><i>Function</i>(<i>arguments</i>) = default;</code></td> |
| <td>Instructs the compiler to generate a default version of the indicated function</td> |
| <td><a href="http://stackoverflow.com/questions/823935/whats-the-point-in-defaulting-functions-in-c11">What's the point in defaulting functions in C++11?</a></td> |
| <td><a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/qgU4mh_MpGA">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Default Function Template Arguments</td> |
| <td><code>template <typename T = <i>type</i>><br /> |
| <i>type</i> <i>Function</i>(T <i>var</i>) {}</code></td> |
| <td>Allow function templates, like classes, to have default arguments</td> |
| <td><a href="http://stackoverflow.com/questions/2447458/default-template-arguments-for-function-templates">Default Template Arguments for Function Templates</a></td> |
| <td><a href="https://groups.google.com/a/chromium.org/forum/#!topic/cxx/9KtaAsome-o">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Delegated Constructors</td> |
| <td><code>Class() : Class(0) {}<br /> |
| Class(<i>type</i> <i>var</i>) : Class(<i>var</i>, 0) {}</code></td> |
| <td>Allow overloaded constructors to use common initialization code</td> |
| <td><a href="https://www.ibm.com/developerworks/community/blogs/5894415f-be62-4bc0-81c5-3956e82276f3/entry/introduction_to_the_c_11_feature_delegating_constructors?lang=en">Introduction to the C++11 feature: delegating constructors</a></td> |
| <td><a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/0zVA8Ctx3Xo">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Enumerated Type Classes and Enum Bases</td> |
| <td><code>enum class <i>classname</i><br /> |
| enum class <i>classname</i> : <i>base-type</i><br /> |
| enum <i>enumname</i> : <i>base-type</i></code></td> |
| <td>Provide enums as full classes, with no implicit conversion to booleans or integers. Provide an explicit underlying type for enum classes and regular enums.</td> |
| <td><a href="http://www.stroustrup.com/C++11FAQ.html#enum">enum-class</a></td> |
| <td>Enum classes are still enums and follow enum naming rules (which means SHOUTY_CASE in the <a href="http://www.chromium.org/developers/coding-style#Naming">Chromium Style Guide</a>). <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/Q5WmkAImanc">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Explicit Conversion Operators</td> |
| <td><code>explicit operator <i>type</i>() { ... }</code></td> |
| <td>Allows conversion operators that cannot be implicitly invoked</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/explicit">explicit specifier</a></td> |
| <td>Prefer to the "safe bool" idiom. <a href="https://groups.google.com/a/chromium.org/d/msg/chromium-dev/zGF1SrQ-1HQ/BAiC12vwPeEJ">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Final Specifier</td> |
| <td><code>final</code></td> |
| <td> Indicates that a class or function is final and cannot be overridden</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/final">final Language Reference</a></td> |
| <td>Recommended for new code. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/VTNZzizN0zo">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Function Suppression</td> |
| <td><code><i>Function</i>(<i>arguments</i>) = delete;</code></td> |
| <td>Suppresses the implementation of a function, especially a synthetic function such as a copy constructor</td> |
| <td>TODO: documentation link</td> |
| <td><a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/i1o7-RNRnMs">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Lambda Expressions</td> |
| <td><code>[<i>captures</i>](<i>params</i>) -> <i>ret</i> { <i>body</i> }</code></td> |
| <td>Anonymous functions</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/lambda">Lambda functions</a></td> |
| <td>Do not bind or store lambdas outside the lifetime of the stack frame they are defined in; use <code>base::Bind</code> and <code>base::Callback</code> instead, because they offer protection against a large class of object lifetime mistakes. Don't use default captures (<code>[=]</code>, <code>[&]</code> – <a href="https://google.github.io/styleguide/cppguide.html#Lambda_expressions">Google Style Guide</a>). Lambdas are typically useful as a parameter to methods or functions that will use them immediately, such as those in <code><algorithm></code>. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/D9UnnxBnciQ">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Local Types as Template Arguments</td> |
| <td><code>void func() {<br /> |
| class Pred {<br /> |
| public:<br /> |
| bool operator()(const T&) { ... }<br /> |
| };<br /> |
| std::remove_if(vec.begin(), vec.end(), Pred());</code></td> |
| <td>Allows local and unnamed types as template arguments</td> |
| <td><a href="http://stackoverflow.com/questions/742607/using-local-classes-with-stl-algorithms">Local types, types without linkage and unnamed types as template arguments</a></td> |
| <td>Usage should be rare. Approved without discussion.</td> |
| </tr> |
| |
| <tr> |
| <td>Non-Static Class Member Initializers</td> |
| <td><code>class C {<br /> |
| <i>type</i> <i>var</i> = <i>value</i>;<br /> |
| C() // copy-initializes <i>var</i></code> |
| <td>Allows non-static class members to be initialized at their definitions (outside constructors)</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/data_members">Non-static data members</a></td> |
| <td><a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/zqB-DySA4V0">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Null Pointer Constant</td> |
| <td><code>nullptr</code></td> |
| <td>Declares a type-safe null pointer</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/nullptr">nullptr</a></td> |
| <td>Prefer over <code>NULL</code> or <code>0</code>. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/4mijeJHzxLg">Discussion thread</a>. <a href="https://google.github.io/styleguide/cppguide.html#0_and_nullptr/NULL">Google Style Guide</a>. <code>std::nullptr_t</code> can be used too.</td> |
| </tr> |
| |
| <tr> |
| <td>Override Specifier</td> |
| <td><code>override</code></td> |
| <td>Indicates that a class or function overrides a base implementation</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/override">override Language Reference</a></td> |
| <td>Recommended for new code. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/VTNZzizN0zo">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Range-Based For Loops</td> |
| <td><code>for (<i>type</i> <i>var</i> : <i>range</i>)</code></td> |
| <td>Facilitates a more concise syntax for iterating over the elements of a container (or a range of iterators) in a <code>for</code> loop</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/range-for">Range-based for loop</a></td> |
| <td>As a rule of thumb, use <code>for (const auto& ...)</code>, <code>for (auto& ...)</code>, or <code>for (<i>concrete type</i> ...)</code>. For pointers, use <code>for (auto* ...)</code> to make clear that the copy of the loop variable is intended, and only a pointer is copied. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/hpzz4EqbVmc">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Rvalue References</td> |
| <td><code>T(T&& t)</code> and <code>T& operator=(T&& t)<br/><br/> |
| template <typename T><br/>void Function(T&& t) { ... }</code></td> |
| <td>Reference that only binds to a temporary object</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/references#Rvalue_references">Rvalue references</a></td> |
| <td>As per the <a href="https://google.github.io/styleguide/cppguide.html#Rvalue_references">Google Style Guide</a>: Only use these to define move constructors and move assignment operators, and for perfect forwarding. Most classes should not be copyable, even if movable. Continue to use DISALLOW_COPY_AND_ASSIGN in most cases. <a href="https://groups.google.com/a/chromium.org/d/topic/chromium-dev/UnRaORb4TSw">Discussion thread</a>. <a href="https://groups.google.com/a/chromium.org/d/topic/cxx/Q526tkruXpM">Another discussion thread</a>.</td> |
| </tr> |
| |
| <tr> |
| <td>Standard Integers</td> |
| <td>Typedefs within <code><stdint.h></code> and <code><inttypes></code></td> |
| <td>Provides fixed-size integers independent of platforms</td> |
| <td><a href="http://www.cplusplus.com/reference/cstdint/"><stdint.h> (cstdint)</a></td> |
| <td>Already in common use in the codebase. Approved without discussion.</td> |
| </tr> |
| |
| <tr> |
| <td>Static Assertions</td> |
| <td><code>static_assert(<i>bool</i>, <i>string</i>)</code></td> |
| <td>Tests compile-time conditions</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/static_assert">Static Assertion</a></td> |
| <td><a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/POISBQEhGzU">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Trailing Return Types</td> |
| <td><code>auto <i>function declaration</i> -> <i>return_type</i></code></td> |
| <td>Allows trailing function return value syntax</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/function">Declaring functions</a></td> |
| <td>Use only where it considerably improves readability. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/OQyYSfH9m2M">Discussion thread</a>. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/cxx/Lkp0nubVd0Q">Another discussion thread.</a></td> |
| </tr> |
| |
| <tr> |
| <td>Uniform Initialization Syntax</td> |
| <td><code><i>type</i> <i>name</i> {[<i>value</i> ..., <i>value</i>]};</code></td> |
| <td>Allows any object of primitive, aggregate or class type to be initialized using brace syntax</td> |
| <td><a href="http://www.stroustrup.com/C++11FAQ.html#uniform-init">Uniform initialization syntax and semantics</a></td> |
| <td>See the <a href="https://www.chromium.org/developers/coding-style/cpp-dos-and-donts?pli=1#TOC-Variable-initialization">Chromium C++ Dos And Don'ts guidance</a> on when to use this. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/GF96FshwHLw">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Variadic Macros</td> |
| <td><code>#define <i>MACRO</i>(...) <i>Impl</i>(<i>args</i>, __VA_ARGS__)</code></td> |
| <td>Allows macros that accept a variable number of arguments</td> |
| <td><a href="http://stackoverflow.com/questions/4786649/are-variadic-macros-nonstandard">Are Variadic macros nonstandard?</a></td> |
| <td>Usage should be rare. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/sRx9j3CQqyA">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Variadic Templates</td> |
| <td><code>template <<i>typename</i> ... <i>arg</i>></code></td> |
| <td>Allows templates that accept a variable number of arguments</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/parameter_pack">Parameter pack</a></td> |
| <td>Usage should be rare. Use instead of .pump files. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/6ItymeMXpMc">Discussion thread</a></td> |
| </tr> |
| |
| </tbody> |
| </table> |
| |
| <h2 id="whitelist"><a name="library-whitelist"></a>C++11 Allowed Library Features</h2> |
| |
| <p>The following library features are currently allowed.</p> |
| |
| <table id="whitelist_lib_list" class="unlined striped"> |
| <tbody> |
| |
| <tr> |
| <th style='width:240px;'>Feature or Library</th> |
| <th style='width:240px;'>Snippet</th> |
| <th style='width:240px;'>Description</th> |
| <th style='width:240px;'>Documentation Link</th> |
| <th style='width:240px;'>Notes</th> |
| </tr> |
| |
| <tr> |
| <td>Access to underlying <code>std::vector</code> data</td> |
| <td><code>v.data()</code></td> |
| <td>Returns a pointer to a <code>std::vector</code>'s underlying data, accounting for empty vectors.</td> |
| <td><a href="http://en.cppreference.com/w/cpp/container/vector/data">std::vector::data</a></td> |
| <td><a href="https://groups.google.com/a/chromium.org/forum/#!topic/cxx/16V7fmtbzok">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Algorithms</td> |
| <td>All C++11 features in <code><algorithm></code>:<br/> |
| <code>all_of</code>, <code>any_of</code>, <code>none_of</code><br/> |
| <code>find_if_not</code><br/> |
| <code>copy_if</code>, <code>copy_n</code><br/> |
| <code>move</code>, <code>move_backward</code> (see note)<br/> |
| <code>shuffle</code><br/> |
| <code>is_partitioned</code>, <code>partition_copy</code>, <code>partition_point</code><br/> |
| <code>is_sorted</code>, <code>is_sorted_until</code><br/> |
| <code>is_heap</code>, <code>is_heap_until</code><br/> |
| <code>minmax</code>, <code>minmax_element</code><br/> |
| <code>is_permutation<br/></td> |
| <td>Safe and performant implementations of common algorithms</td> |
| <td><a href="http://en.cppreference.com/w/cpp/header/algorithm"><algorithm></a></td> |
| <td><a href="https://groups.google.com/a/chromium.org/forum/#!topic/cxx/UJQk8S1IuHk">Discussion thread</a><br/> Note that <algorithm> contains a range-based <code>move</code> method. This is allowed, but because people may confuse it with the single-arg <code>std::move</code>, there is often a way to write code without it that is more readable. <a href='https://groups.google.com/a/chromium.org/forum/#!topic/cxx/8WzmtYrZvQ8'>Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Begin and End Non-Member Functions</td> |
| <td><code>std::begin()</code>, <code>std::end()</code></td> |
| <td>Allows use of free functions on any container, including fixed-size arrays</td> |
| <td><a href="http://en.cppreference.com/w/cpp/iterator/begin">std::begin</a>, <a href="http://en.cppreference.com/w/cpp/iterator/end">std::end</a></td> |
| <td>Useful for fixed-size arrays. Note that non-member <code>cbegin()</code> and <code>cend()</code> are not available until C++14. <a href="https://groups.google.com/a/chromium.org/d/topic/cxx/5iFNE8P5qT4/discussion">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Conditional Type Selection</td> |
| <td><code>std::enable_if</code>, <code>std::conditional</code></td> |
| <td>Enables compile-time conditional type selection</td> |
| <td><a href="http://en.cppreference.com/w/cpp/types/enable_if">std::enable_if</a>, <a href="http://en.cppreference.com/w/cpp/types/conditional">conditional</a></td> |
| <td>Usage should be rare. <a href='https://groups.google.com/a/chromium.org/forum/#!topic/cxx/vCxo4tZNd_M'>Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Constant Iterator Methods on Containers</td> |
| <td>E.g. <code>std::vector::cbegin()</code>, <code>std::vector::cend()</code></td> |
| <td>Allows more widespread use of <code>const_iterator</code></td> |
| <td><a href="http://en.cppreference.com/w/cpp/container/vector/begin">std::vector::cbegin</a>, <a href="http://en.cppreference.com/w/cpp/container/vector/end">std::vector::cend<a></td> |
| <td>Applies to all containers, not just <code>vector</code>. Consider using <code>const_iterator</code> over <code>iterator</code> where possible for the same reason as using <code>const</code> variables and functions where possible; see Effective Modern C++ item 13 for motivation. <a href="https://groups.google.com/a/chromium.org/d/topic/cxx/cS83F_buqLM/discussion">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Containers containing movable types</td> |
| <td><code>vector<scoped_ptr></code></td> |
| <td>Enables containers that contain move-only types like <code>scoped_ptr</code></td> |
| <td>TODO</td> |
| <td>Prefer over <a href="http://crbug.com/554289">ScopedVector</a>.</td> |
| </tr> |
| |
| <tr> |
| <td>Declared Type As Value</td> |
| <td><code>std::declval<<i>class</i>>()</code></td> |
| <td>Converts a type to a reference of the type to allow use of members of the type without constructing it in templates.</td> |
| <td><a href="http://en.cppreference.com/w/cpp/utility/declval">std::declval</a></td> |
| <td>Usage should be rare. <a href="https://groups.google.com/a/chromium.org/d/topic/cxx/ku6lYjk0-OU/discussion">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Emplacement methods for containers</td> |
| <td><code>emplace()</code>, <code>emplace_back()</code>, <code>emplace_front()</code>, <code>emplace_hint()</code></td> |
| <td>Constructs elements directly within a container without a copy or a move. Less verbose than <code>push_back()</code> due to not naming the type being constructed.</td> |
| <td>E.g. <a href="http://en.cppreference.com/w/cpp/container/vector/emplace_back">std::vector::emplace_back</a></td> |
| <td><code>std::map::emplace()</code> is not yet available on all libstdc++ versions we support. When using emplacement for performance reasons, your type should probably be movable (since e.g. a vector of it might be resized); given a movable type, then, consider whether you really need to avoid the move done by <code>push_back()</code>. For readability concerns, treat like <code>auto</code>; sometimes the brevity over <code>push_back()</code> is a win, sometimes a loss. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/cxx/m3cblzEta7A">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Forwarding references</td> |
| <td><code>std::forward()</code></td> |
| <td>Perfectly forwards arguments (including rvalues)</td> |
| <td><a href="http://en.cppreference.com/w/cpp/utility/forward">std::forward</a></td> |
| <td>Allowed, though usage should be rare (primarily for forwarding constructor arguments, or in carefully reviewed library code). <a href="https://groups.google.com/a/chromium.org/d/topic/cxx/-O7euklhSxs/discussion">Discussion thread</a> |
| </td> |
| </tr> |
| |
| <tr> |
| <td>Initializer Lists</td> |
| <td><code>std::initializer_list<T></code></td> |
| <td>Allows containers to be initialized with aggregate elements</td> |
| <td><a href="http://en.cppreference.com/w/cpp/utility/initializer_list">std::initializer_list</a></td> |
| <td>Be cautious adding new constructors which take these, as they can hide non-initializer_list constructors in undesirable ways; see Effective Modern C++ Item 7 for more.</td> |
| </tr> |
| |
| <tr> |
| <td>Math functions</td> |
| <td>All C++11 features in <code><cmath></code>, e.g.:<br/> |
| <code>INFINITY</code>, <code>NAN</code>, <code>FP_NAN</code><br/> |
| <code>float_t</code>, <code>double_t</code><br/> |
| <code>fmax</code>, <code>fmin</code>, <code>trunc</code>, <code>round</code><br/> |
| <code>isinf</code>, <code>isnan</code><br/></td> |
| <td>Useful for math-related code</td> |
| <td><a href="http://en.cppreference.com/w/cpp/header/cmath"><cmath></a></td> |
| <td><a href="https://groups.google.com/a/chromium.org/forum/#!topic/cxx/P-1bFBXMeUk">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Move Iterator Adaptor</td> |
| <td><code>std::make_move_iterator()</code></td> |
| <td>Wraps an iterator so that it moves objects instead of copying them.</td> |
| <td><a href="http://en.cppreference.com/w/cpp/iterator/make_move_iterator">std::make_move_iterator</a></td> |
| <td>Useful to move objects between containers that contain move-only types like <code>scoped_ptr</code>. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/cxx/lccnUljOHQU">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Move Semantics</td> |
| <td><code>std::move()</code></td> |
| <td>Facilitates efficient move operations</td> |
| <td><a href="http://en.cppreference.com/w/cpp/utility/move">std::move</a></td> |
| <td><a href='https://groups.google.com/a/chromium.org/forum/#!topic/cxx/x_dWFxJFdbM'>Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>String Direct Reference Functions</td> |
| <td><code>std::string::front()</code>, <code>std::string::back()</code></td> |
| <td>Returns a reference to the front or back of a string</td> |
| <td><a href="http://en.cppreference.com/w/cpp/string/basic_string/front">std::basic_string::front</a>, <a href="http://en.cppreference.com/w/cpp/string/basic_string/back">std::basic_string::back</a></td> |
| <td><a href="https://groups.google.com/a/chromium.org/forum/#!topic/cxx/DRJuROAYCV4">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Type Traits</td> |
| <td>All C++11 features in <code><type_traits></code> except for aligned storage (see separate item), e.g.:<br/> |
| <code>integral_constant</code><br/> |
| <code>is_floating_point</code>, <code>is_rvalue_reference</code>, <code>is_scalar</code><br/> |
| <code>is_const</code>, <code>is_pod</code>, <code>is_unsigned</code><br/> |
| <code>is_default_constructible</code>, <code>is_move_constructible</code>, <code>is_copy_assignable</code><br/> |
| <code>enable_if</code>, <code>conditional</code>, <code>result_of</code><br/></td> |
| <td>Allows compile-time inspection of the properties of types</td> |
| <td><a href="http://en.cppreference.com/w/cpp/header/type_traits"><type_traits></a></td> |
| <td>Note that not all type traits are available on all platforms (e.g. <code>std::underlying_type</code> doesn't work in libstdc++4.6). Use judiciously. <a href='https://groups.google.com/a/chromium.org/forum/#!topic/cxx/vCxo4tZNd_M'>Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Tuples</td> |
| <td>All C++11 features in <code><tuple></code>, e.g. <code>std::tie</code> and <code>std::tuple</code>.</td> |
| <td>A fixed-size ordered collection of values of mixed types</td> |
| <td><a href="http://en.cppreference.com/w/cpp/header/tuple"><tuple></a></td> |
| <td>Prefer <code>std::tuple</code> over <a href="https://crbug.com/554987"><code>base::Tuple</code></a>.</td> |
| </tr> |
| |
| <tr> |
| <td>Unordered Associative Containers</td> |
| <td><code>std::unordered_set</code>, <code>std::unordered_map</code>, <code>std::unordered_multiset</code>, <code>std::unordered_multimap</code></td> |
| <td>Allows efficient containers of key/value pairs</td> |
| <td><a href="http://en.cppreference.com/w/cpp/container/unordered_map">std::unordered_map</a>, <a href="http://en.cppreference.com/w/cpp/container/unordered_set">std::unordered_set</a></td> |
| <td>Per the <a href="https://google.github.io/styleguide/cppguide.html#std_hash">Google Style Guide</a>, specify custom hashers instead of specializing <code>std::hash</code> for custom types. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/cxx/nCdjQqnouO4">Discussion thread</a>.</td> |
| </tr> |
| |
| <tr> |
| <td>Unique Pointers</td> |
| <td><code>std::unique_ptr<<i>type</i>></code></td> |
| <td>A smart pointer with sole ownership of the owned object.</td> |
| <td><a href="http://en.cppreference.com/w/cpp/memory/unique_ptr">std::unique_ptr</a></td> |
| <td>Use in all newly written code. <a href="https://google.github.io/styleguide/cppguide.html#Ownership_and_Smart_Pointers">Google Style Guide</a>. <a href="https://groups.google.com/a/chromium.org/d/msg/cxx/aT2wsBLKvzI/oZuZ718oAwAJ">Discussion thread</a>. <code>scoped_ptr</code> is a <a href="https://groups.google.com/a/chromium.org/d/msg/chromium-dev/roY78iTblYc/bb8nYsxfCgAJ">typedef for <code>std::unique_ptr</code></a> and is going away shortly.</td> |
| </tr> |
| |
| </tbody> |
| </table> |
| |
| <h2 id="blacklist">C++11 Blacklist (Disallowed and Banned Features)</h2> |
| |
| <p>This section lists features that are not allowed to be used yet. |
| |
| <h3 id="blacklist_banned"><a name="core-blacklist"></a>C++11 Banned Features</h3> |
| |
| <p>This section lists C++11 features that are not allowed in the Chromium |
| codebase. |
| </p> |
| |
| <table id="banned_list" class="unlined striped"> |
| <tbody> |
| |
| <tr> |
| <th style='width:240px;'>Feature or Library</th> |
| <th style='width:240px;'>Snippet</th> |
| <th style='width:240px;'>Description</th> |
| <th style='width:240px;'>Documentation Link</th> |
| <th style='width:240px;'>Notes</th> |
| </tr> |
| |
| <tr> |
| <td>Alignment Features</td> |
| <td><code>alignas</code> specifier, <code>alignof</code> operator</td> |
| <td>Object alignment</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/alignas">alignas</a>, <a href="http://en.cppreference.com/w/cpp/language/alignof">alignof</a></td> |
| <td>Reevaluate now that MSVS2015 is available. <a href="https://groups.google.com/a/chromium.org/d/msg/cxx/rwXN02jzzq0/CpUc1ZzMBQAJ">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Function Local Variable</td> |
| <td><code>__func__</code></td> |
| <td>Provides a local variable of the name of the enclosing function for logging purposes</td> |
| <td><a href="http://www.informit.com/guides/content.aspx?g=cplusplus&seqNum=338">The __func__ Predeclared Identifier is Coming to C++</a></td> |
| <td>Reevaluate now that MSVS2015 is available. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/ojGfcgSDzHM">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Inherited Constructors</td> |
| <td><code>class Derived : Base {<br /> |
| using Base::Base;<br /> |
| };</code></td> |
| <td>Allow derived classes to inherit constructors from base classes</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/using_declaration">Using-declaration</a></td> |
| <td>Reevaluate now that MSVS2015 is available. <a href="https://groups.google.com/a/chromium.org/d/msg/chromium-dev/BULzgIKZ-Ao/PLO7_GoVNvYJ">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td><code>long long</code> Type</td> |
| <td><code>long long <i>var</i>= <i>value</i>;</code></td> |
| <td>An integer of at least 64 bits</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/types">Fundamental types</a></td> |
| <td>Use a stdint.h type if you need a 64bit number. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/RxugZ-pIDxk">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Raw String Literals</td> |
| <td><code>string <i>var</i>=R"(<i>raw_string</i>)";</code></td> |
| <td>Allows a string to be encoded without any escape sequences, easing parsing in regex expressions, for example</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/string_literal">string literal</a></td> |
| <td>Causes incorrect line numbers in MSVS2013 and gcc. Reevaluate once that works. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/2kWQHbbuMHI">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>UTF-16 and UTF-32 Support (16-Bit and 32-Bit Character Types)</td> |
| <td><code>char16_t</code> and <code>char32_t</code></td> |
| <td>Provides character types for handling 16-bit and 32-bit code units (useful for encoding UTF-16 and UTF-32 string data)</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/types">Fundamental types</a></td> |
| <td>Reevaluate now that MSVS2015 is available. Non-UTF-8 text is banned by the <a href="https://google.github.io/styleguide/cppguide.html#Non-ASCII_Characters">Google Style Guide</a>. However, may be useful for consuming non-ASCII data. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/ME2kL7_Kvyk">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>UTF-8, UTF-16, UTF-32 String Literals</td> |
| <td><code>u8"<i>string</i>", u"<i>string</i>", U"<i>string</i>"</code></td> |
| <td>Enforces UTF-8, UTF-16, UTF-32 encoding on all string literals</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/string_literal">string literal</a></td> |
| <td>Reevaluate now that MSVS2015 is available. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/gcoUbcjfsII">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Ref-qualified Member Functions</td> |
| <td><code>class T {<br /> |
| void f() & {}<br /> |
| void f() && {}<br /> |
| };<br /> |
| t.f(); // first<br /> |
| T().f(); // second<br /> |
| std::move(t).f(); // second</code></td> |
| <td>Allows class member functions to only bind to |this| as an rvalue or lvalue.</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/member_functions">Member functions</a></td> |
| <td>Banned in the <a href="https://google.github.io/styleguide/cppguide.html#C++11">Google Style Guide</a>. Banned in Chromium except by explicit approval from <code>styleguide/c++/OWNERS</code>. <a href="https://groups.google.com/a/chromium.org/d/topic/cxx/gowclr2LPQA/discussion">Discussion Thread</a></td> |
| </tr> |
| |
| </tbody> |
| </table> |
| |
| <h3 id="blacklist_stdlib"><a name="library-blacklist"></a>C++11 Banned Library Features</h3> |
| |
| <p>This section lists C++11 library features that are not allowed in the Chromium codebase.</p> |
| |
| <table id="blacklist_lib_list" class="unlined striped"> |
| <tbody> |
| |
| <tr> |
| <th style='width:240px;'>Feature</th> |
| <th style='width:240px;'>Snippet</th> |
| <th style='width:240px;'>Description</th> |
| <th style='width:240px;'>Documentation Link</th> |
| <th style='width:240px;'>Notes</th> |
| </tr> |
| |
| <tr> |
| <td>Chrono Library</td> |
| <td><code><chrono></code></td> |
| <td>Provides a standard date and time library</td> |
| <td><a href="http://en.cppreference.com/w/cpp/chrono">Date and time utilities</a></td> |
| <td>Duplicated <code>Time</code> APIs in <code>base/</code>. Keep using the <code>base/</code> classes.</td> |
| </tr> |
| |
| <tr> |
| <td>Regex Library</td> |
| <td><code><regex></code></td> |
| <td>Provides a standard regular expressions library</td> |
| <td><a href="http://en.cppreference.com/w/cpp/regex">Regular expressions library</a></td> |
| <td>We already have too many regular expression libraries in Chromium. Use re2 when in doubt.</td> |
| </tr> |
| |
| <tr> |
| <td>Thread Library</td> |
| <td><code><thread></code> support, including<br /> |
| <code><future></code>, <code><mutex></code>, <code><condition_variable></code></td> |
| <td>Provides a standard mulitthreading library using <code>std::thread</code> and associates</td> |
| <td><a href="http://en.cppreference.com/w/cpp/thread">Thread support library</a></td> |
| <td>C++11 has all kinds of classes for threads, mutexes, etc. Since we already have good code for this in <code>base/</code>, we should keep using the base classes, at least at first. <code>base::Thread</code> is tightly coupled to <code>MessageLoop</code> which would make it hard to replace. We should investigate using standard mutexes, or unique_lock, etc. to replace our locking/synchronization classes.</td> |
| </tr> |
| |
| <tr> |
| <td>Atomics</td> |
| <td><code>std::atomic</code> and others in <code><atomic></code></td> |
| <td>Fine-grained atomic types and operations</td> |
| <td><a href="http://en.cppreference.com/w/cpp/atomic"><atomic></a></td> |
| <td>Use in tcmalloc has caused <a href="http://crbug.com/572525">performance regressions</a>. Banned until we understand this better. <a href="https://groups.google.com/a/chromium.org/d/topic/cxx/Ej3RAiaI44s/discussion">Discussion Thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Shared Pointers</td> |
| <td><code>std::shared_ptr</code></td> |
| <td>Allows shared ownership of a pointer through reference counts</td> |
| <td><a href="http://en.cppreference.com/w/cpp/memory/shared_ptr">std::shared_ptr</a></td> |
| <td>Needs a lot more evaluation for Chromium, and there isn't enough of a push for this feature. <a href="https://google.github.io/styleguide/cppguide.html#Ownership_and_Smart_Pointers">Google Style Guide</a>. <a href="https://groups.google.com/a/chromium.org/d/topic/cxx/aT2wsBLKvzI/discussion">Discussion Thread</a>.</td> |
| </tr> |
| |
| </tbody> |
| </table> |
| |
| |
| <h3 id="blacklist_review"><a name="core-review"></a>C++11 Features To Be Discussed</h3> |
| |
| <p>The following C++ language features are currently disallowed. |
| See the top of this page on how to propose moving a feature from this list |
| into the allowed or banned sections. Note that not all of these features |
| work in all our compilers yet.</p> |
| |
| <table id="blacklist_review_list" class="unlined striped"> |
| <tbody> |
| |
| <tr> |
| <th style='width:240px;'>Feature</th> |
| <th style='width:240px;'>Snippet</th> |
| <th style='width:240px;'>Description</th> |
| <th style='width:240px;'>Documentation Link</th> |
| <th style='width:240px;'>Notes</th> |
| </tr> |
| |
| <tr> |
| <td>Attributes</td> |
| <td><code>[[<i>attribute_name</i>]]</code></td> |
| <td>Attaches properties to declarations that specific compiler implementations may use.</td> |
| <td><a href="http://www.codesynthesis.com/~boris/blog/2012/04/18/cxx11-generalized-attributes/">C++11 generalized attributes</a></td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>Exception Features</td> |
| <td><code>noexcept</code>, <code>exception_ptr</code>, <code>current_exception()</code>, <code>rethrow_exception</code>, <code>nested_exception</code></td> |
| <td>Enhancements to exception throwing and handling</td> |
| <td><a href="http://en.cppreference.com/w/cpp/error/exception">std::exception</a></td> |
| <td>Exceptions are banned by the <a href="https://google.github.io/styleguide/cppguide.html#Exceptions">Google Style Guide</a>. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/8i4tMqNpHhg">Discussion thread</a></td> |
| </tr> |
| |
| <tr> |
| <td>Inline Namespaces</td> |
| <td><code>inline</code></td> |
| <td>Allows better versioning of namespaces</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/namespace">Namespaces</a></td> |
| <td>Unclear how it will work with components</td> |
| </tr> |
| |
| <tr> |
| <td>Union Class Members</td> |
| <td><code>union <i>name</i> {<i>class</i> <i>var</i>}</code></td> |
| <td>Allows class type members</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/union">Union declarations</a></td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>User-Defined Literals</td> |
| <td><code><i>type</i> <i>var</i> = <i>literal_value</i>_<i>type</i></code></td> |
| <td>Allows user-defined literal expressions</td> |
| <td><a href="http://en.cppreference.com/w/cpp/language/user_literal">User-defined literals</a></td> |
| <td></td> |
| </tr> |
| |
| </tbody> |
| </table> |
| |
| <h3 id="blacklist_stdlib_review"><a name="library-review"></a>C++11 Standard Library Features To Be Discussed</h3> |
| |
| <p>The following C++ library features are currently disallowed. See the top of this page on how to propose moving a feature from this list into the allowed or banned sections. Note that not all of these features work in all our compilers yet.</p> |
| |
| <table id="banned_stdlib" class="unlined striped"> |
| |
| <tbody> |
| <tr> |
| <th style='width:240px;'>Feature</th> |
| <th style='width:240px;'>Snippet</th> |
| <th style='width:240px;'>Description</th> |
| <th style='width:240px;'>Documentation Link</th> |
| <th style='width:240px;'>Style Guide Usage</th> |
| </tr> |
| |
| <tr> |
| <td>Address Retrieval</td> |
| <td><code>std::addressof()</code></td> |
| <td>Obtains the address of an object even with overloaded <code>operator&</code></td> |
| <td><a href="http://en.cppreference.com/w/cpp/memory/addressof">std::addressof</a></td> |
| <td>Usage should be rare as <a href="https://google.github.io/styleguide/cppguide.html#Operator_Overloading">operator overloading</a> is rare and <code>&</code> should suffice in most cases. May be preferable over <code>&</code> for performing object identity checks.</td> |
| </tr> |
| |
| <tr> |
| <td>Aligned Storage</td> |
| <td><code>std::aligned_storage<Size, Align>::type</code><br /> |
| <code>std::alignment_of<T></code>, <code>std::aligned_union<Size, ...Types></code> <code>std::max_align_t</code></td> |
| <td>Declare uninitialized storage having a specified alignment, or determine alignments.</td> |
| <td><a href="http://en.cppreference.com/w/cpp/types/aligned_storage">std::aligned_storage</a></td> |
| <td><code>std::aligned_storage</code> and <code>std::aligned_union</code> are disallowed in google3 over concerns about compatibility with internal cross-compiling toolchains.</td> |
| </tr> |
| |
| <tr> |
| <td>Allocator Traits</td> |
| <td><code>std::allocator_traits</code></td> |
| <td>Provides an interface for accessing custom allocators</td> |
| <td><a href="http://en.cppreference.com/w/cpp/memory/allocator_traits">std::allocator_traits</a></td> |
| <td>Usage should be rare.</td> |
| </tr> |
| |
| <tr> |
| <td>Bind Operations</td> |
| <td><code>std::bind(<i>function</i>, <i>args</i>, ...)</code></td> |
| <td>Declares a function object bound to certain arguments</td> |
| <td>TODO: documentation link</td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>C Floating-Point Environment</td> |
| <td><code><cfenv></code>, <code><fenv.h></code></td> |
| <td>Provides floating point status flags and control modes for C-compatible code</td> |
| <td><a href="http://en.cppreference.com/w/cpp/header/cfenv">Standard library header <cfenv></a></td> |
| <td>Banned in <a href="https://google.github.io/styleguide/cppguide.html#C++11">Google Style Guide</a> due to concerns about compiler support.</td> |
| </tr> |
| |
| <tr> |
| <td>Complex Inverse Trigonometric and Hyperbolic Functions</td> |
| <td>Functions within <code><complex></code></td> |
| <td>Adds inverse trigonomentric and hyperbolic non-member functions to the <code><complex></code> library.</td> |
| <td><a href="http://en.cppreference.com/w/cpp/numeric/complex">std::complex</a></td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>Container Compaction Functions</td> |
| <td><code>std::vector::shrink_to_fit()</code>, <code>std::deque::shrink_to_fit()</code>, <code>std::string::shrink_to_fit()</code></td> |
| <td>Requests the removal of unused space in the container</td> |
| <td><a href="http://en.cppreference.com/w/cpp/container/vector/shrink_to_fit">std::vector::shrink_to_fit</a>, <a href="http://en.cppreference.com/w/cpp/container/deque/shrink_to_fit">std::deque::shrink_to_fit</a>, <a href="http://en.cppreference.com/w/cpp/string/basic_string/shrink_to_fit">std::basic_string::shrink_to_fit</a></td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>Date/Time String Formatting Specifiers</td> |
| <td><code>std::strftime()</code></td> |
| <td>Converts date and time information into a formatted string using new specifiers</td> |
| <td><a href="http://en.cppreference.com/w/cpp/chrono/c/strftime">std::strftime</a></td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>Function Return Type Deduction</td> |
| <td><code>std::result_of<<i>Functor(ArgTypes...)</i>></code></td> |
| <td>Extracts the return type from the type signature of a function call invocation at compile-time.</td> |
| <td><a href="http://en.cppreference.com/w/cpp/types/result_of">std::result_of</a></td> |
| <td><a href="http://stackoverflow.com/questions/15486951/why-does-stdresult-of-take-an-unrelated-function-type-as-a-type-argument">Why does std::result_of take an (unrelated) function type as a type argument?</a></td> |
| </tr> |
| |
| <tr> |
| <td>Function Objects</td> |
| <td><code>std::function</code></td> |
| <td>Wraps a standard polymorphic function</td> |
| <td>TODO: documentation link</td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>Forward Lists</td> |
| <td><code>std::forward_list</code></td> |
| <td>Provides an efficient singly linked list</td> |
| <td><a href="http://en.cppreference.com/w/cpp/container/forward_list">std::forward_list</a></td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>Gamma Natural Log</td> |
| <td><code>std::lgamma()</code></td> |
| <td>Computes the natural log of the gamma of a floating point value</td> |
| <td><a href="http://en.cppreference.com/w/cpp/numeric/math/lgamma">std::lgamma</a></td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>Garbage Collection Features</td> |
| <td><code>std::{un}declare_reachable()</code>, <code>std::{un}declare_no_pointers()</code></td> |
| <td>Enables garbage collection implementations</td> |
| <td><a href="http://en.cppreference.com/w/cpp/memory/gc/declare_reachable">std::declare_reachable</a>, <a href="http://en.cppreference.com/w/cpp/memory/gc/declare_no_pointers">std::declare_no_pointers</a></td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>Iterator Operators</td> |
| <td><code>std::next()</code>, <code>std::prev()</code></td> |
| <td>Copies an iterator and increments or decrements the copy by some value</td> |
| <td><a href="http://en.cppreference.com/w/cpp/iterator/next">std::next</a>, <a href="http://en.cppreference.com/w/cpp/iterator/prev">std::prev</a></td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>Pointer Traits Class Template</td> |
| <td><code>std::pointer_traits</code></td> |
| <td>Provides a standard way to access properties of pointers and pointer-like types</td> |
| <td><a href="http://en.cppreference.com/w/cpp/memory/pointer_traits">std::pointer_traits</a></td> |
| <td>Useful for determining the element type pointed at by a (possibly smart) pointer.</td> |
| </tr> |
| |
| <tr> |
| <td>Random Number Generators</td> |
| <td>Functions within <code><random></code></td> |
| <td>Random number generation algorithms and utilities</td> |
| <td><a href="http://en.cppreference.com/w/cpp/numeric/random">Pseudo-random number generation</a></td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>Ratio Template Class</td> |
| <td><code>std::ratio<<i>numerator</i>, <i>denominator</i>></code></td> |
| <td>Provides compile-time rational numbers</td> |
| <td><a href="http://en.cppreference.com/w/cpp/numeric/ratio/ratio">std::ratio</a></td> |
| <td>Banned in <a href="https://google.github.io/styleguide/cppguide.html#C++11">Google Style Guide</a> due to concerns that they are tied to a more template-heavy interface style.</td> |
| </tr> |
| |
| <tr> |
| <td>Reference Wrapper Classes</td> |
| <td><code>std::reference_wrapper</code> and <code>std::ref()</code>, <code>std::cref()</code></td> |
| <td>Allows you to wrap a reference within a standard object (and use those within containers)</td> |
| <td><a href="http://www.informit.com/guides/content.aspx?g=cplusplus&seqNum=217">Reference Wrappers</a></td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>Soft Program Exits</td> |
| <td><code>std::at_quick_exit()</code>, <code>std::quick_exit()</code></td> |
| <td>Allows registration of functions to be called upon exit, allowing cleaner program exit than <code>abort()</code> or <code>exit</code></td> |
| <td><a href="http://en.cppreference.com/w/cpp/utility/program/quick_exit">std:quick_exit</a></td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>String to Number Functions</td> |
| <td><code>std::stoi()</code>, <code>std::stol()</code>, <code>std::stoul()</code>, <code>std::stoll</code>, <code>std::stoull()</code>, <code>std::stof()</code>, <code>std::stod()</code>, <code>std::stold()</code>, <code>std::to_string()</code></td> |
| <td>Converts strings to numbers</td> |
| <td><a href="http://en.cppreference.com/w/cpp/string/basic_string/stol">std::stoi, std::stol, std::stoll</a>, <a href="http://en.cppreference.com/w/cpp/string/basic_string/stoul">std::stoul, std::stoull</a>, <a href="http://en.cppreference.com/w/cpp/string/basic_string/stof">std::stof, std::stod, std::stold</a></td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>System Errors</td> |
| <td><code><system_error></code></td> |
| <td>Provides a standard system error library</td> |
| <td><a href="http://en.cppreference.com/w/cpp/error/system_error">std::system_error</a></td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>Type-Generic Math Functions</td> |
| <td>Functions within <code><ctgmath></code></td> |
| <td>Provides a means to call real or complex functions based on the type of arguments</td> |
| <td><a href="http://en.cppreference.com/w/cpp/header/ctgmath">Standard library header <ctgmath></a></td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>Type Info Enhancements</td> |
| <td><code>std::type_index</code>, <code>std::type_info::hash_code()</code></td> |
| <td>Allows type information (most often within containers) that can be copied, assigned, or hashed</td> |
| <td><a href="http://en.cppreference.com/w/cpp/types/type_index">std::type_index</a>, <a href="http://en.cppreference.com/w/cpp/types/type_info/hash_code">std::type_info::hash_code</a></td> |
| <td><code>std::type_index</code> is a thin wrapper for <code>std::type_info</code>, allowing you to use it directly within both associative and unordered containers</td> |
| </tr> |
| |
| <tr> |
| <td>Variadic Copy Macro</td> |
| <td><code>va_copy(va_list <i>dest</i>, va_list <i>src</i>)</code></td> |
| <td>Makes a copy of the variadic function arguments</td> |
| <td></td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>Weak Pointers</td> |
| <td><code>std::weak_ptr</code></td> |
| <td>Allows a weak reference to a <code>std::shared_ptr</code></td> |
| <td><a href="http://en.cppreference.com/w/cpp/memory/weak_ptr">std::weak_ptr</a></td> |
| <td><a href="https://google.github.io/styleguide/cppguide.html#Ownership_and_Smart_Pointers">Ownership and Smart Pointers</a></td> |
| </tr> |
| |
| <tr> |
| <td>Wide String Support</td> |
| <td><code>std::wstring_convert</code>, <code>std::wbuffer_convert</code><br /> |
| <code>std::codecvt_utf8</code>, <code>std::codecvt_utf16</code>, <code>std::codecvt_utf8_utf16</code></td> |
| <td>Converts between string encodings</td> |
| <td><a href="http://en.cppreference.com/w/cpp/locale/wstring_convert">std::wstring_convert</a>, <a href="http://en.cppreference.com/w/cpp/locale/wbuffer_convert">std::wbuffer_convert</a>, <a href="http://en.cppreference.com/w/cpp/locale/codecvt_utf8">std::codecvt_utf8</a>, <a href="http://en.cppreference.com/w/cpp/locale/codecvt_utf16">std::codecvt_utf16</a>, <a href="http://en.cppreference.com/w/cpp/locale/codecvt_utf8_utf16">std::codecvt_utf8_utf16</a></td> |
| <td>Non-UTF-8 text is banned by the <a href="https://google.github.io/styleguide/cppguide.html#Non-ASCII_Characters">Google Style Guide</a>. However, may be useful for consuming non-ASCII data.</td> |
| </tr> |
| |
| </tbody> |
| </table> |
| |
| </div> |
| </body> |
| </html> |