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3<section id="frequently-asked-questions">
4<h1 id="frequently-asked-questions">Frequently Asked Questions</h1>
[email protected]26420f22014-01-24 18:06:135<div class="contents local" id="contents" style="display: none">
[email protected]bde3d5d2014-01-23 19:26:046<ul class="small-gap">
[email protected]81156022014-07-09 22:04:557<li><p class="first"><a class="reference internal" href="#what-is-native-client-good-for" id="id1">What is Native Client Good For?</a></p>
[email protected]bde3d5d2014-01-23 19:26:048<ul class="small-gap">
[email protected]81156022014-07-09 22:04:559<li><a class="reference internal" href="#why-did-google-build-native-client" id="id2">Why did Google build Native Client?</a></li>
10<li><a class="reference internal" href="#when-should-i-use-portable-native-client-instead-of-native-client" id="id3">When should I use Portable Native Client instead of Native Client?</a></li>
11<li><a class="reference internal" href="#when-should-i-use-portable-native-client-native-client" id="id4">When should I use Portable Native Client / Native Client?</a></li>
12<li><a class="reference internal" href="#how-fast-does-code-run-in-portable-native-client" id="id5">How fast does code run in Portable Native Client?</a></li>
13<li><a class="reference internal" href="#why-use-portable-native-client-instead-of-technology-x" id="id6">Why use Portable Native Client instead of <em>&lt;technology X&gt;</em>?</a></li>
14<li><a class="reference internal" href="#if-i-want-direct-access-to-the-os-should-i-use-native-client" id="id7">If I want direct access to the OS, should I use Native Client?</a></li>
[email protected]bde3d5d2014-01-23 19:26:0415</ul>
16</li>
[email protected]81156022014-07-09 22:04:5517<li><p class="first"><a class="reference internal" href="#development-environments-and-tools" id="id8">Development Environments and Tools</a></p>
[email protected]bde3d5d2014-01-23 19:26:0418<ul class="small-gap">
[email protected]81156022014-07-09 22:04:5519<li><a class="reference internal" href="#what-development-environment-and-development-operating-system-do-you-recommend" id="id9">What development environment and development operating system do you recommend?</a></li>
20<li><a class="reference internal" href="#i-m-not-familiar-with-native-development-tools-can-i-still-use-the-native-client-sdk" id="id10">I&#8217;m not familiar with native development tools, can I still use the Native Client SDK?</a></li>
[email protected]bde3d5d2014-01-23 19:26:0421</ul>
22</li>
[email protected]81156022014-07-09 22:04:5523<li><p class="first"><a class="reference internal" href="#openness-and-supported-architectures-and-languages" id="id11">Openness, and Supported Architectures and Languages</a></p>
[email protected]bde3d5d2014-01-23 19:26:0424<ul class="small-gap">
[email protected]81156022014-07-09 22:04:5525<li><a class="reference internal" href="#is-native-client-open-is-it-a-standard" id="id12">Is Native Client open? Is it a standard?</a></li>
26<li><a class="reference internal" href="#what-are-the-supported-instruction-set-architectures" id="id13">What are the supported instruction set architectures?</a></li>
27<li><a class="reference internal" href="#do-i-have-to-use-c-or-c-i-d-really-like-to-use-another-language" id="id14">Do I have to use C or C++? I&#8217;d really like to use another language.</a></li>
28<li><a class="reference internal" href="#do-you-only-support-chrome-what-about-other-browsers" id="id15">Do you only support Chrome? What about other browsers?</a></li>
29<li><a class="reference internal" href="#what-s-the-difference-between-npapi-and-pepper" id="id16">What&#8217;s the difference between NPAPI and Pepper?</a></li>
30<li><a class="reference internal" href="#is-npapi-part-of-the-native-client-sdk" id="id17">Is NPAPI part of the Native Client SDK?</a></li>
31<li><a class="reference internal" href="#does-native-client-support-simd-vector-instructions" id="id18">Does Native Client support SIMD vector instructions?</a></li>
32<li><a class="reference internal" href="#can-i-use-native-client-for-3d-graphics" id="id19">Can I use Native Client for 3D graphics?</a></li>
33<li><a class="reference internal" href="#does-native-client-support-concurrency-parallelism" id="id20">Does Native Client support concurrency/parallelism?</a></li>
[email protected]bde3d5d2014-01-23 19:26:0434</ul>
35</li>
[email protected]81156022014-07-09 22:04:5536<li><p class="first"><a class="reference internal" href="#coming-soon" id="id21">Coming Soon</a></p>
[email protected]bde3d5d2014-01-23 19:26:0437<ul class="small-gap">
[email protected]81156022014-07-09 22:04:5538<li><a class="reference internal" href="#do-native-client-modules-have-access-to-external-devices" id="id22">Do Native Client modules have access to external devices?</a></li>
[email protected]bde3d5d2014-01-23 19:26:0439</ul>
40</li>
[email protected]81156022014-07-09 22:04:5541<li><p class="first"><a class="reference internal" href="#security-and-privacy" id="id23">Security and Privacy</a></p>
[email protected]bde3d5d2014-01-23 19:26:0442<ul class="small-gap">
[email protected]81156022014-07-09 22:04:5543<li><a class="reference internal" href="#what-happens-to-my-data-when-i-use-native-client" id="id24">What happens to my data when I use Native Client?</a></li>
44<li><a class="reference internal" href="#how-does-native-client-prevent-sandboxed-code-from-doing-bad-things" id="id25">How does Native Client prevent sandboxed code from doing Bad Things?</a></li>
45<li><a class="reference internal" href="#how-does-google-know-that-the-safety-measures-in-native-client-are-sufficient" id="id26">How does Google know that the safety measures in Native Client are sufficient?</a></li>
[email protected]bde3d5d2014-01-23 19:26:0446</ul>
47</li>
[email protected]81156022014-07-09 22:04:5548<li><p class="first"><a class="reference internal" href="#development" id="id27">Development</a></p>
[email protected]bde3d5d2014-01-23 19:26:0449<ul class="small-gap">
[email protected]81156022014-07-09 22:04:5550<li><a class="reference internal" href="#how-do-i-debug" id="id28">How do I debug?</a></li>
51<li><a class="reference internal" href="#how-do-i-build-x86-32-x86-64-or-arm-nexes" id="id29">How do I build x86-32, x86-64 or ARM <code>.nexes</code>?</a></li>
52<li><a class="reference internal" href="#how-can-my-web-application-determine-which-nexe-to-load" id="id30">How can my web application determine which <code>.nexe</code> to load?</a></li>
53<li><a class="reference internal" href="#is-it-possible-to-build-a-native-client-module-with-just-plain-c-not-c" id="id31">Is it possible to build a Native Client module with just plain C (not C++)?</a></li>
54<li><a class="reference internal" href="#what-unix-system-calls-can-i-make-through-native-client" id="id32">What UNIX system calls can I make through Native Client?</a></li>
55<li><a class="reference internal" href="#is-my-favorite-third-party-library-available-for-native-client" id="id33">Is my favorite third-party library available for Native Client?</a></li>
56<li><a class="reference internal" href="#do-all-the-files-in-an-application-need-to-be-served-from-the-same-domain" id="id34">Do all the files in an application need to be served from the same domain?</a></li>
[email protected]bde3d5d2014-01-23 19:26:0457</ul>
58</li>
[email protected]81156022014-07-09 22:04:5559<li><p class="first"><a class="reference internal" href="#portability" id="id35">Portability</a></p>
[email protected]bde3d5d2014-01-23 19:26:0460<ul class="small-gap">
[email protected]81156022014-07-09 22:04:5561<li><a class="reference internal" href="#do-i-have-to-do-anything-special-to-make-my-application-run-on-different-operating-systems" id="id36">Do I have to do anything special to make my application run on different operating systems?</a></li>
62<li><a class="reference internal" href="#how-easy-is-it-to-port-my-existing-native-code-to-native-client" id="id37">How easy is it to port my existing native code to Native Client?</a></li>
[email protected]bde3d5d2014-01-23 19:26:0463</ul>
64</li>
[email protected]81156022014-07-09 22:04:5565<li><p class="first"><a class="reference internal" href="#troubleshooting" id="id38">Troubleshooting</a></p>
[email protected]bde3d5d2014-01-23 19:26:0466<ul class="small-gap">
[email protected]81156022014-07-09 22:04:5567<li><a class="reference internal" href="#my-pexe-isn-t-loading-help" id="id39">My <code>.pexe</code> isn&#8217;t loading, help!</a></li>
68<li><a class="reference internal" href="#my-nexe-files-never-finish-loading-what-gives" id="id40">My <code>.nexe</code> files never finish loading. What gives?</a></li>
[email protected]bde3d5d2014-01-23 19:26:0469</ul>
70</li>
71</ul>
[email protected]26420f22014-01-24 18:06:1372
73</div><p>This document answers some frequently asked questions about Native
[email protected]bde3d5d2014-01-23 19:26:0474Client (NaCl) and Portable Native Client (PNaCl, pronounced
75&#8220;pinnacle&#8221;). For a high-level overview of Native Client, see the
76<a class="reference internal" href="/native-client/overview.html"><em>Technical Overview</em></a>.</p>
77<p>If you have questions that aren&#8217;t covered in this FAQ:</p>
78<ul class="small-gap">
79<li>Scan through the <a class="reference internal" href="/native-client/sdk/release-notes.html"><em>Release Notes</em></a>.</li>
80<li>Search through or ask on the <a class="reference internal" href="/native-client/help.html"><em>Native Client Forums</em></a>.</li>
81</ul>
[email protected]bde3d5d2014-01-23 19:26:0482<h2 id="what-is-native-client-good-for">What is Native Client Good For?</h2>
[email protected]bde3d5d2014-01-23 19:26:0483<h3 id="why-did-google-build-native-client">Why did Google build Native Client?</h3>
84<ul class="small-gap">
85<li><strong>Performance:</strong> Native Client modules run nearly as fast as native
86compiled code.</li>
87<li><strong>Security:</strong> Native Client lets users run native compiled code in the
88browser with the same level of security and privacy as traditional web
89applications.</li>
90<li><p class="first"><strong>Convenience:</strong></p>
91<ul class="small-gap">
92<li>Developers can leverage existing code, written in C/C++ or other
93languages, in their applications without forcing users to install a
94plugin.</li>
95<li>This code can interact with the embedding web page as part of an
96HTML and JavaScript web application, or it can be a self-contained
97and immersive experience.</li>
98</ul>
99</li>
100<li><p class="first"><strong>Portability:</strong> Native Client and Portable Native Client applications
101can execute on:</p>
102<ul class="small-gap">
103<li>The Windows, Mac, Linux or ChromeOS operating systems.</li>
104<li>Processors with the x86-32, x86-64, or ARM instruction set
105architectures. Native Client also has experimental support for MIPS.</li>
106</ul>
107</li>
108</ul>
109<p>Portable Native client further enhances the above:</p>
110<ul class="small-gap">
111<li><strong>Performance:</strong> Each PNaCl release brings with it more performance
112enhancements. Already-released applications get faster over time,
113conserving user&#8217;s battery.</li>
114<li><strong>Security:</strong> Users are kept secure with an ever-improving sandbox
115model which adapts to novel attacks, without affecting
116already-released applications.</li>
117<li><strong>Convenience:</strong> Developers only need to ship a single <code>.pexe</code> file,
118not one <code>.nexe</code> file per supported architecture.</li>
119<li><strong>Portability:</strong> Developers and users don&#8217;t need to worry about
120already-released applications not working on new hardware: PNaCl
121already supports all architectures NaCl does, and as PNaCl evolves it
122gains support for new processors and fully uses their capabilities.</li>
123</ul>
124<p>For more details, refer to the <a class="reference internal" href="/native-client/nacl-and-pnacl.html"><em>history behind and comparison of
125NaCl and PNaCl</em></a>.</p>
[email protected]81156022014-07-09 22:04:55126<h3 id="when-should-i-use-portable-native-client-instead-of-native-client">When should I use Portable Native Client instead of Native Client?</h3>
127<p>See <a class="reference internal" href="/native-client/nacl-and-pnacl.html"><em>NaCl and PNaCl</em></a>. In short: PNaCl works on the Open
128Web platform delivered by Chrome whereas NaCl only works on the Chrome Web
129Store.</p>
[email protected]81156022014-07-09 22:04:55130<h3 id="when-should-i-use-portable-native-client-native-client">When should I use Portable Native Client / Native Client?</h3>
[email protected]bde3d5d2014-01-23 19:26:04131<p>The following are some typical use cases. For details, see the
132<a class="reference internal" href="/native-client/overview.html"><em>Technical Overview</em></a>.</p>
133<ul class="small-gap">
[email protected]81156022014-07-09 22:04:55134<li>Porting existing applications or software components, written in C/C++ or
135virtual machines written in C/C++, for use in a web application.</li>
136<li><p class="first">Using compute-intensive applications, including threads and SIMD, such as:</p>
137<ul class="small-gap">
138<li>Scientific computing.</li>
[email protected]bde3d5d2014-01-23 19:26:04139<li>Handling multimedia for a web application.</li>
[email protected]81156022014-07-09 22:04:55140<li>Various aspects of web-based games, including physics engines and AI.</li>
[email protected]bde3d5d2014-01-23 19:26:04141</ul>
[email protected]81156022014-07-09 22:04:55142</li>
143<li>Running untrusted code on a server or within an application (such as a plugin
144system for a game).</li>
145</ul>
146<p>Portable Native Client and Native Client are versatile technologies which are
[email protected]bde3d5d2014-01-23 19:26:04147used in many other contexts outside of Chrome.</p>
[email protected]bde3d5d2014-01-23 19:26:04148<h3 id="how-fast-does-code-run-in-portable-native-client">How fast does code run in Portable Native Client?</h3>
149<p>Fast! The SPEC2k benchmarks (C, C++ and floating-point benchmarks) give
150the following overhead for optimized PNaCl compared to regular optimized
151LLVM:</p>
152<table border="1" class="docutils">
153<colgroup>
154</colgroup>
155<tbody valign="top">
156<tr class="row-odd"><td>x86-32</td>
157<td>15%</td>
158</tr>
159<tr class="row-even"><td>x86-64</td>
160<td>25%</td>
161</tr>
162<tr class="row-odd"><td>ARM</td>
163<td>10%</td>
164</tr>
165</tbody>
166</table>
167<p>Note that benchmark performance is sometimes bimodal, so different use
168cases are likely to achieve better or worse performance than the above
169averages. For example floating-point heavy code usually exhibits much
170lower overheads whereas very branch-heavy code often performs worse.</p>
[email protected]2d46b9b2014-04-24 17:07:45171<p>Note that PNaCl supports performance features that are often used in
172native code such as <a class="reference internal" href="/native-client/reference/pnacl-c-cpp-language-support.html#language-support-threading"><em>threading</em></a> and
173<a class="reference internal" href="/native-client/reference/pnacl-c-cpp-language-support.html#portable-simd-vectors"><em>Portable SIMD Vectors</em></a>.</p>
[email protected]bde3d5d2014-01-23 19:26:04174<p>For details, see:</p>
175<ul class="small-gap">
[email protected]81156022014-07-09 22:04:55176<li><a class="reference external" href="https://www.youtube.com/watch?v=675znN6tntw&amp;list=PLOU2XLYxmsIIwGK7v7jg3gQvIAWJzdat_">PNaCl SIMD: Speed on the Web</a>.</li>
[email protected]bde3d5d2014-01-23 19:26:04177<li><a class="reference external" href="https://nativeclient.googlecode.com/svn/data/site/NaCl_SFI.pdf">Adapting Software Fault Isolation to Contemporary CPU Architectures</a> (PDF).</li>
178<li><a class="reference external" href="http://research.google.com/pubs/pub34913.html">Native Client: A Sandbox for Portable, Untrusted x86 Code</a> (PDF).</li>
179</ul>
180<p>If your code isn&#8217;t performing as close to native speed as you&#8217;d expect,
181<a class="reference internal" href="/native-client/help.html"><em>let us know</em></a>!</p>
[email protected]bde3d5d2014-01-23 19:26:04182<h3 id="why-use-portable-native-client-instead-of-technology-x">Why use Portable Native Client instead of <em>&lt;technology X&gt;</em>?</h3>
183<p>Many other technologies can be compared to Portable Native Client:
184Flash, Java, Silverlight, ActiveX, .NET, asm.js, etc...</p>
185<p>Different technologies have different strengths and weaknesses. In
186appropriate contexts, Portable Native Client can be faster, more secure,
187and/or more compatible across operating systems and architectures than
188other technologies.</p>
189<p>Portable Native Client complement other technologies by giving web
190developers a new capability: the ability to run fast, secure native code
191from a web browser in an architecture-independent way.</p>
[email protected]bde3d5d2014-01-23 19:26:04192<h3 id="if-i-want-direct-access-to-the-os-should-i-use-native-client">If I want direct access to the OS, should I use Native Client?</h3>
193<p>No&#8212;Native Client does not provide direct access to the OS or devices,
194or otherwise bypass the JavaScript security model. For more information,
195see later sections of this FAQ.</p>
[email protected]bde3d5d2014-01-23 19:26:04196<h2 id="development-environments-and-tools">Development Environments and Tools</h2>
[email protected]bde3d5d2014-01-23 19:26:04197<h3 id="what-development-environment-and-development-operating-system-do-you-recommend">What development environment and development operating system do you recommend?</h3>
[email protected]81156022014-07-09 22:04:55198<p>You can develop on Windows, Mac, or Linux, and the resulting Native Client or
199Portable Native Client application will run inside the Google Chrome browser on
200all those platforms as well as ChromeOS. You can also develop on ChromeOS with
201<a class="reference external" href="https://github.com/dnschneid/crouton">Crouton</a> or our <a class="reference external" href="https://www.youtube.com/watch?v=OzNuzBDEWzk&amp;list=PLOU2XLYxmsIIwGK7v7jg3gQvIAWJzdat_">experimental development environment which runs within NaCl</a>,
202and we&#8217;re working on self-hosting a full development environment on Portable
203Native Client.</p>
[email protected]bde3d5d2014-01-23 19:26:04204<p>Any editor+shell combination should work as well as IDEs like Eclipse,
205Visual Studio with the <a class="reference internal" href="/native-client/devguide/devcycle/vs-addin.html"><em>Native Client Add-In</em></a> on Windows, or Xcode on Mac OSX.</p>
[email protected]bde3d5d2014-01-23 19:26:04206<h3 id="i-m-not-familiar-with-native-development-tools-can-i-still-use-the-native-client-sdk">I&#8217;m not familiar with native development tools, can I still use the Native Client SDK?</h3>
207<p>You may find our <a class="reference internal" href="/native-client/devguide/tutorial/index.html"><em>Tutorial</em></a> and <a class="reference internal" href="/native-client/devguide/devcycle/building.html"><em>Building
208instructions</em></a> useful, and you can look at
209the code and Makefiles for the SDK examples to understand how the
210examples are built and run.</p>
[email protected]81156022014-07-09 22:04:55211<p>You&#8217;ll need to learn how to use some tools (like GCC, LLVM, make, Eclipse,
212Visual Studio, or Xcode) before you can get very far with the SDK. Try seaching
213for an <a class="reference external" href="https://www.google.com/search?q=gcc+introduction">introduction to GCC</a>.</p>
[email protected]bde3d5d2014-01-23 19:26:04214<h2 id="openness-and-supported-architectures-and-languages">Openness, and Supported Architectures and Languages</h2>
[email protected]bde3d5d2014-01-23 19:26:04215<h3 id="is-native-client-open-is-it-a-standard">Is Native Client open? Is it a standard?</h3>
216<p>Native Client is completely open: the executable format is open and the
[email protected]46daa952014-07-11 18:08:44217<a class="reference external" href="https://code.google.com/p/nativeclient/">source code is open</a>. Right
[email protected]bde3d5d2014-01-23 19:26:04218now the Native Client project is in its early stages, so it&#8217;s premature
219to consider Native Client for standardization.</p>
220<p>We consistenly try to document our design and implementation and hope to
221standardize Portable Native Client when it gains more traction. A good
222example is our <a class="reference internal" href="/native-client/reference/pnacl-bitcode-abi.html"><em>PNaCl bitcode reference manual</em></a>.</p>
[email protected]bde3d5d2014-01-23 19:26:04223<h3 id="what-are-the-supported-instruction-set-architectures">What are the supported instruction set architectures?</h3>
224<p>Portable Native Client uses an architecture-independent format (the
225<code>.pexe</code>) which can currently be translated to execute on processors
226with the x86-32, x86-64, and ARM instruction set architectures, as well
227as experimental support for MIPS. As new architectures come along and
228become popular we expect Portable Native Client to support them without
229developers having to recompile their code.</p>
230<p>Native Client can currently execute on the same architectures as
231Portable Native Client but is only supported on the Chrome Web
232Store. Native Client&#8217;s <code>.nexe</code> files are architecture-dependent and
233cannot adapt to new architectures without recompilation, we therefore
234deem them better suited to a web store than to the open web.</p>
235<p>With Portable Native Client we deliver a system that has comparable
236portability to JavaScript and can adapt to new instruction set
237architectures without requiring recompilation. The web is better when
238it&#8217;s platform-independent, and we&#8217;d like it to stay that way.</p>
[email protected]c3c19f12014-08-06 18:01:43239<h3 id="do-i-have-to-use-c-or-c-i-d-really-like-to-use-another-language"><span id="other-languages"></span>Do I have to use C or C++? I&#8217;d really like to use another language.</h3>
[email protected]81156022014-07-09 22:04:55240<p>Right now only C and C++ are supported directly by the toolchain in the SDK. C#
241and other languages in the .NET family are supported via the <a class="reference external" href="https://github.com/elijahtaylor/mono">Mono port</a> for
242Native Client. Moreover, there are several ongoing projects to support
243additional language runtimes (e.g. <a class="reference external" href="https://code.google.com/p/naclports/source/browse#svn%2Ftrunk%2Fsrc%2Fexamples%2Ftools">naclports supports Lua, Python and Ruby</a>)
244as well as to compile more languages to LLVM&#8217;s intermediate representation
245(e.g. support <a class="reference external" href="http://halide-lang.org/">Halide</a>, Haskell with <a class="reference external" href="http://www.haskell.org/ghc/docs/latest/html/users_guide/code-generators.html">GHC</a> or support Fortran with <a class="reference external" href="https://flang-gsoc.blogspot.ie/2013/09/end-of-gsoc-report.html">flang</a>), or
JF Bastiend8377eb2015-01-19 18:06:14246transpile languages to C/C++ (source-to-source compilation). Even JavaScript is
247supported by compiling <a class="reference external" href="https://code.google.com/p/v8/">V8</a> to target PNaCl.</p>
248<p>The PNaCl toolchain is built on LLVM and can therefore generate code from
249languages such as <a class="reference external" href="http://www.rust-lang.org/">Rust</a>, <a class="reference external" href="https://golang.org">Go</a>, or Objective-C, but there may still be a few rough
250edges.</p>
[email protected]bde3d5d2014-01-23 19:26:04251<p>If you&#8217;re interested in getting other languages working, please contact the
[email protected]81156022014-07-09 22:04:55252Native Client team by way of the <a class="reference external" href="https://groups.google.com/group/native-client-discuss">native-client-discuss</a> mailing list.</p>
[email protected]81156022014-07-09 22:04:55253<h3 id="do-you-only-support-chrome-what-about-other-browsers">Do you only support Chrome? What about other browsers?</h3>
[email protected]bde3d5d2014-01-23 19:26:04254<p>We aim to support multiple browsers. However, a number of features that
255we consider requirements for a production-quality system that keeps the
256user safe are difficult to implement without help from the
257browser. Specific examples are an out-of-process plugin architecture and
258appropriate interfaces for integrated 3D graphics. We have worked
259closely with Chromium developers to deliver these features and we are
260eager to collaborate with developers from other browsers.</p>
[email protected]bde3d5d2014-01-23 19:26:04261<h3 id="what-s-the-difference-between-npapi-and-pepper">What&#8217;s the difference between NPAPI and Pepper?</h3>
262<p><a class="reference internal" href="/native-client/pepper_stable/index.html"><em>Pepper</em></a> (also known as PPAPI) is a new API that
263lets Native Client modules communicate with the browser. Pepper supports
264various features that don&#8217;t have robust support in NPAPI, such as event
265handling, out-of-process plugins, and asynchronous interfaces. Native
266Client has transitioned from using NPAPI to using Pepper.</p>
[email protected]bde3d5d2014-01-23 19:26:04267<h3 id="is-npapi-part-of-the-native-client-sdk">Is NPAPI part of the Native Client SDK?</h3>
[email protected]81156022014-07-09 22:04:55268<p>NPAPI is not supported by the Native Client SDK, and is <a class="reference external" href="http://blog.chromium.org/2013/09/saying-goodbye-to-our-old-friend-npapi.html">deprecated in Chrome</a>.</p>
[email protected]bde3d5d2014-01-23 19:26:04269<h3 id="does-native-client-support-simd-vector-instructions">Does Native Client support SIMD vector instructions?</h3>
[email protected]2d46b9b2014-04-24 17:07:45270<p>Portable Native Client supports portable SIMD vectors, as detailed in
271<a class="reference internal" href="/native-client/reference/pnacl-c-cpp-language-support.html#portable-simd-vectors"><em>Portable SIMD Vectors</em></a>.</p>
JF Bastien8084a6a02015-02-02 18:02:31272<p>Native Client supports SSE, AVX1, FMA3 and AVX2 (except for <cite>VGATHER</cite>) on x86
273and NEON on ARM.</p>
[email protected]bde3d5d2014-01-23 19:26:04274<h3 id="can-i-use-native-client-for-3d-graphics">Can I use Native Client for 3D graphics?</h3>
275<p>Yes. Native Client supports <a class="reference external" href="https://www.khronos.org/opengles/">OpenGL ES 2.0</a>.</p>
276<p>To alert the user regarding their hardware platform&#8217;s 3D feature set
277before loading a large NaCl application, see <a class="reference internal" href="/native-client/devguide/coding/3D-graphics.html"><em>Vetting the driver in
278Javascript</em></a>.</p>
[email protected]81156022014-07-09 22:04:55279<p>Some GL extensions are exposed to Native Client applications, see the <a class="reference external" href="https://code.google.com/p/chromium/codesearch#chromium/src/ppapi/lib/gl/gles2/gles2.c">GLES2
280file</a>. This file is part of the GL wrapper supplied by the library
281<code>ppapi_gles2</code> which you&#8217;ll want to include in your project. In most cases
282extensions map to extensions available on other platforms, or differ very
283slightly (if they differ, the extension is usually CHROMIUM or ANGLE instead of
284EXT).</p>
[email protected]bde3d5d2014-01-23 19:26:04285<h3 id="does-native-client-support-concurrency-parallelism">Does Native Client support concurrency/parallelism?</h3>
286<p>Native Client and Portable Native Client both support pthreads,
287C11/C++11 threads, and low-level synchronization primitives (mutex,
288barriers, atomic read/modify/write, compare-and-exchange, etc...), thus
289allowing your Native Client application to utilize several CPU cores.
290Note that this allows you to modify datastructures concurrently without
291needing to copy them, which is often a limitation of shared-nothing
292systems. For more information see <a class="reference internal" href="/native-client/reference/pnacl-c-cpp-language-support.html#memory-model-and-atomics"><em>memory model and atomics</em></a> and <a class="reference internal" href="/native-client/reference/pnacl-c-cpp-language-support.html#language-support-threading"><em>threading</em></a>.</p>
293<p>Native Client doesn&#8217;t support HTML5 Web Workers directly but can
294interact with JavaScript code which does.</p>
[email protected]bde3d5d2014-01-23 19:26:04295<h2 id="coming-soon">Coming Soon</h2>
[email protected]bde3d5d2014-01-23 19:26:04296<h3 id="do-native-client-modules-have-access-to-external-devices">Do Native Client modules have access to external devices?</h3>
297<p>At this time Native Client modules do not have access to serial ports,
298camera devices, or microphones: Native Client can only use native
299resources that today&#8217;s browsers can access. However, we intend to
300recommend such features to the standards bodies and piggyback on their
301efforts to make these resources available inside the browser.</p>
302<p>You can generally think of Pepper as the C/C++ bindings to the
303capabilities of HTML5. The goal is for Pepper and JavaScript to evolve
304together and stay on par with each other with respect to features and
305capabilities.</p>
[email protected]bde3d5d2014-01-23 19:26:04306<h2 id="security-and-privacy">Security and Privacy</h2>
[email protected]bde3d5d2014-01-23 19:26:04307<h3 id="what-happens-to-my-data-when-i-use-native-client">What happens to my data when I use Native Client?</h3>
308<p>Users can opt-in to sending usage statistics and crash information in
309Chrome, which includes usage statistics and crash information about
310Native Client. Crashes in your code won&#8217;t otherwise send your
311information to Google: Google counts the number of such crashes, but
312does so anonymously without sending your application&#8217;s data or its debug
313information.</p>
[email protected]81156022014-07-09 22:04:55314<p>For additional information about privacy and Chrome, see the <a class="reference external" href="https://www.google.com/chrome/intl/en/privacy.html">Google Chrome
315privacy policy</a> and the <a class="reference external" href="https://www.google.com/chrome/intl/en/eula_text.html">Google Chrome Terms of Service</a>.</p>
[email protected]bde3d5d2014-01-23 19:26:04316<h3 id="how-does-native-client-prevent-sandboxed-code-from-doing-bad-things">How does Native Client prevent sandboxed code from doing Bad Things?</h3>
317<p>Native Client&#8217;s sandbox works by validating the untrusted code (the
318compiled Native Client module) before running it. The validator checks
319the following:</p>
320<ul class="small-gap">
321<li><strong>Data integrity:</strong> No loads or stores are permitted outside of the
322data sandbox. In particular this means that once loaded into memory,
323the binary is not writable. This is enforced by operating system
324protection mechanisms. While new instructions can be inserted at
325runtime to support things like JIT compilers, such instructions will
326be subject to runtime verification according to the following
327constraints before they are executed.</li>
328<li><strong>No unsafe instructions:</strong> The validator ensures that the Native
329Client application does not contain any unsafe instructions. Examples
330of unsafe instructions are <code>syscall</code>, <code>int</code>, and <code>lds</code>.</li>
331<li><strong>Control flow integrity:</strong> The validator ensures that all direct and
332indirect branches target a safe instruction.</li>
333</ul>
334<p>The beauty of the Native Client sandbox is in reducing &#8220;safe&#8221; code to a
335few simple rules that can be verified by a small trusted validator: the
336compiler isn&#8217;t trusted. The same applies to Portable Native Client where
337even the <code>.pexe</code> to <code>.nexe</code> translator, a simplified compiler
338backend, isn&#8217;t trusted: it is validated before executing, and so is its
339output.</p>
[email protected]81156022014-07-09 22:04:55340<p>In addition to static analysis of untrusted code, the Native Client runtime also
341includes an outer sandbox that mediates system calls. For more details about
342both sandboxes, see <a class="reference external" href="http://research.google.com/pubs/pub34913.html">Native Client: A Sandbox for Portable, Untrusted x86 Code</a>
[email protected]bde3d5d2014-01-23 19:26:04343(PDF).</p>
[email protected]bde3d5d2014-01-23 19:26:04344<h3 id="how-does-google-know-that-the-safety-measures-in-native-client-are-sufficient">How does Google know that the safety measures in Native Client are sufficient?</h3>
[email protected]81156022014-07-09 22:04:55345<p>Google has taken several steps to ensure that Native Client&#8217;s security works,
346including:</p>
[email protected]bde3d5d2014-01-23 19:26:04347<ul class="small-gap">
348<li>Open source, peer-reviewed papers describing the design.</li>
349<li>A <a class="reference internal" href="/native-client/community/security-contest/index.html"><em>security contest</em></a>.</li>
350<li>Multiple internal and external security reviews.</li>
351<li>The ongoing vigilance of our engineering and developer community.</li>
352</ul>
[email protected]81156022014-07-09 22:04:55353<p>Google is committed to making Native Client safer than JavaScript and other
354popular browser technologies. If you have suggestions for security improvements,
355let the team know, by way of the <a class="reference external" href="https://groups.google.com/group/native-client-discuss">native-client-discuss</a> mailing list.</p>
[email protected]bde3d5d2014-01-23 19:26:04356<h2 id="development">Development</h2>
[email protected]bde3d5d2014-01-23 19:26:04357<h3 id="how-do-i-debug">How do I debug?</h3>
358<p>Instructions on <a class="reference internal" href="/native-client/sdk/examples.html#debugging-the-sdk-examples"><em>debugging the SDK examples</em></a> using GDB are available. You can also
359debug Native Client modules with some <a class="reference internal" href="/native-client/devguide/devcycle/debugging.html"><em>alternative approaches</em></a>.</p>
[email protected]bde3d5d2014-01-23 19:26:04360<h3 id="how-do-i-build-x86-32-x86-64-or-arm-nexes">How do I build x86-32, x86-64 or ARM <code>.nexes</code>?</h3>
361<p>By default, the applications in the <code>/examples</code> folder create
362architecture-independent <code>.pexe</code> for Portable Native Client. To
363generate a <code>.nexe</code> targetting one specific architecture using the
364Native Client or Portable Native Client toolchains, see the
365<a class="reference internal" href="/native-client/devguide/devcycle/building.html"><em>Building instructions</em></a>.</p>
[email protected]bde3d5d2014-01-23 19:26:04366<h3 id="how-can-my-web-application-determine-which-nexe-to-load">How can my web application determine which <code>.nexe</code> to load?</h3>
367<p>Your application does not need to make the decision of loading an
368x86-32, x86-64 or ARM <code>.nexe</code> explicitly&#8212;the Native Client runtime
369examines a manifest file (<code>.nmf</code>) to pick the right <code>.nexe</code> file for
370a given user. You can generate a manifest file using a Python script
371that&#8217;s included in the SDK (see the <code>Makefile</code> in any of the SDK
372examples for an illustration of how to do so). Your HTML file specifies
373the manifest filename in the <code>src</code> attribute of the <code>&lt;embed&gt;</code>
374tag. You can see the way the pieces fit together by examining the
375examples included in the SDK.</p>
[email protected]bde3d5d2014-01-23 19:26:04376<h3 id="is-it-possible-to-build-a-native-client-module-with-just-plain-c-not-c">Is it possible to build a Native Client module with just plain C (not C++)?</h3>
377<p>Yes. See the <code>&quot;Hello, World!&quot;</code> in C example in the SDK under
378<code>examples/tutorial/using_ppapi_simple/</code>, or the Game of Life example
379under <code>examples/demo/life/life.c</code>.</p>
[email protected]bde3d5d2014-01-23 19:26:04380<h3 id="what-unix-system-calls-can-i-make-through-native-client">What UNIX system calls can I make through Native Client?</h3>
381<p>Native Client doesn&#8217;t directly expose any system calls from the host OS
382because of the inherent security risks and because the resulting
383application would not be portable across operating systems. Instead,
384Native Client provides portable cross-OS abstractions wrapping or
385proxying OS functionality or emulating UNIX system calls. For example,
386Native Client provides an <code>mmap()</code> system call that behaves much like
387the standard UNIX <code>mmap()</code> system call.</p>
[email protected]bde3d5d2014-01-23 19:26:04388<h3 id="is-my-favorite-third-party-library-available-for-native-client">Is my favorite third-party library available for Native Client?</h3>
[email protected]81156022014-07-09 22:04:55389<p>Google has ported several third-party libraries to Native Client; such libraries
390are available in the <a class="reference external" href="https://code.google.com/p/naclports">naclports</a> project. We encourage you to contribute
391libraries to naclports, and/or to host your own ported libraries, and to let the
392team know about it on <a class="reference external" href="https://groups.google.com/group/native-client-discuss">native-client-discuss</a> when you do.</p>
[email protected]bde3d5d2014-01-23 19:26:04393<h3 id="do-all-the-files-in-an-application-need-to-be-served-from-the-same-domain">Do all the files in an application need to be served from the same domain?</h3>
394<p>The <code>.nmf</code>, and <code>.nexe</code> or <code>.pexe</code> files must either be served from the
395same origin as the embedding page or an origin that has been configured
396correctly using <a class="reference external" href="http://en.wikipedia.org/wiki/Cross-origin_resource_sharing">CORS</a>.</p>
397<p>For applications installed from the Chrome Web Store the Web Store manifest
398must include the correct, verified domain of the embedding page.</p>
[email protected]bde3d5d2014-01-23 19:26:04399<h2 id="portability">Portability</h2>
[email protected]bde3d5d2014-01-23 19:26:04400<h3 id="do-i-have-to-do-anything-special-to-make-my-application-run-on-different-operating-systems">Do I have to do anything special to make my application run on different operating systems?</h3>
401<p>No. Native Client and Portable Native Client applications run without
402modification on all supported operating systems.</p>
403<p>However, to run on different instruction set architectures (such as
404x86-32, x86-64 or ARM), you currently have to either:</p>
405<ul class="small-gap">
406<li>Use Portable Native Client.</li>
407<li>Build and supply a separate <code>.nexe</code> file for each architecture, and
408make them available on the Chrome Web Store. See <a class="reference internal" href="/native-client/devguide/devcycle/building.html"><em>target
409architectures</em></a> for details about which
410<code>.nexe</code> files will run on which architectures.</li>
411</ul>
[email protected]bde3d5d2014-01-23 19:26:04412<h3 id="how-easy-is-it-to-port-my-existing-native-code-to-native-client">How easy is it to port my existing native code to Native Client?</h3>
413<p>In most cases you won&#8217;t have to rewrite much, if any, code. The Native
414Client-specific tools, such as <code>pnacl-clang++</code> or <code>x86_64-nacl-g++</code>,
415take care of most of the necessary changes. You may need to make some
416changes to your operating system calls and interactions with external
417devices to work with the web. Porting existing Linux libraries is
418generally straightforward, with large libraries often requiring no
419source change.</p>
420<p>The following kinds of code may be more challenging to port:</p>
421<ul class="small-gap">
jfbbd7a2732015-02-09 18:22:10422<li>Code that does direct <a class="reference external" href="pepper_stable/cpp/classpp_1_1_u_d_p_socket">TCP</a> or
423<a class="reference external" href="pepper_stable/cpp/classpp_1_1_u_d_p_socket">UDP</a> networking. For security
424reasons these APIs are only available to <a class="reference external" href="/apps/about_apps">packaged applications</a> after asking for the appropriate permissions, not on the
425open web. Native Client is otherwise restricted to the networking APIs
426available in the browser. You may want to use to <a class="reference external" href="nacl_io">nacl_io library</a>
427to use POSIX-like sockets.</li>
428<li>Code that creates processes, including UNIX <code>fork</code>, won&#8217;t function
429as-is. However, threads are supported. You can nonetheless create new
430<code>&lt;embed&gt;</code> tags in your HTML page to launch new PNaCl processes, even using
431new <code>.pexe</code> files that your existing <code>.pexe</code> saved in a local
432filesystem. This is somewhat akin to <code>execve</code>, but the process management
433has to go through <code>postMessage</code> to JavaScript in order to create the new
434<code>&lt;embed&gt;</code>.</li>
435<li>Code that needs to do local file I/O. Native Client is restricted to accessing
436URLs and to local storage in the browser (the Pepper <a class="reference internal" href="/native-client/devguide/coding/file-io.html"><em>File IO API</em></a> has access to the same per-application storage that
437JavaScript has via Local Storage). HTML5 File System can be used, among
438others. For POSIX compatabiliy the Native Client SDK includes a library called
439nacl_io which allows the application to interact with all these types of files
440via standard POSIX I/O functions (e.g. <code>open</code> / <code>fopen</code> / <code>read</code> /
441<code>write</code> / ...). See <a class="reference internal" href="/native-client/devguide/coding/nacl_io.html"><em>Using NaCl I/O</em></a> for more
442details.</li>
[email protected]bde3d5d2014-01-23 19:26:04443</ul>
[email protected]c3c19f12014-08-06 18:01:43444<h2 id="troubleshooting"><span id="faq-troubleshooting"></span>Troubleshooting</h2>
[email protected]bde3d5d2014-01-23 19:26:04445<h3 id="my-pexe-isn-t-loading-help">My <code>.pexe</code> isn&#8217;t loading, help!</h3>
446<ul class="small-gap">
447<li>You must use Google Chrome version 31 or greater for Portable Native
jfbbd7a2732015-02-09 18:22:10448Client. Find your version of chrome by opening <code>about:chrome</code>, and <a class="reference external" href="http://www.google.com/chrome/">update
449Chrome</a> if you are on an older version. If
450you&#8217;re already using a recent version, open <code>about:components</code> and &#8220;Check
451for update&#8221; for PNaCl. Note that on ChromeOS PNaCl is always up to date,
452whereas on other operating systems it updates shortly after Chrome updates.</li>
jmedleya7749732014-11-05 15:19:55453<li>A PNaCl <code>.pexe</code> must be compiled with pepper_31 SDK or higher. <a class="reference internal" href="/native-client/sdk/download.html#updating-bundles"><em>Update
454your bundles</em></a> and make sure you&#8217;re using a version of
455Chrome that matches the SDK version.</li>
[email protected]bde3d5d2014-01-23 19:26:04456<li>Your application can verify that Portable Native Client is supported
457in JavaScript with <code>navigator.mimeTypes['application/x-pnacl'] !==
458undefined</code>. This is preferred over checking the Chrome version.</li>
459</ul>
[email protected]bde3d5d2014-01-23 19:26:04460<h3 id="my-nexe-files-never-finish-loading-what-gives">My <code>.nexe</code> files never finish loading. What gives?</h3>
461<p>Here are ways to resolve some common problems that can prevent loading:</p>
462<ul class="small-gap">
463<li>You must use Google Chrome version 14 or greater for Native Client.</li>
464<li>If you haven&#8217;t already done so, enable the Native Client flag in
465Google Chrome. Type <code>about:flags</code> in the Chrome address bar, scroll
466down to &#8220;Native Client&#8221;, click the &#8220;Enable&#8221; link, scroll down to the
467bottom of the page, and click the &#8220;Relaunch Now&#8221; button (all browser
468windows will restart).</li>
469<li>Verify that the Native Client plugin is enabled in Google Chrome. Type
470<code>about:plugins</code> in the Chrome address bar, scroll down to &#8220;Native
471Client&#8221;, and click the &#8220;Enable&#8221; link. (You do not need to relaunch
472Chrome after you enable the Native Client plugin).</li>
473<li>Make sure that the <code>.nexe</code> files are being served from a web
474server. Native Client uses the same-origin security policy, which
475means that modules will not load in pages opened with the <code>file://</code>
476protocol. In particular, you can&#8217;t run the examples in the SDK by
477simply dragging the HTML files from the desktop into the browser. See
478<a class="reference internal" href="/native-client/devguide/devcycle/running.html"><em>Running Native Client Applications</em></a>
479for instructions on how to run the httpd.py mini-server included in
480the SDK.</li>
481<li>The <code>.nexe</code> files must have been compiled using SDK version 0.5 or
482greater.</li>
483<li>You must load the correct <code>.nexe</code> file for your machine&#8217;s specific
484instruction set architecture (x86-32, x86-64 or ARM). You can ensure
485you&#8217;re loading the correct <code>.nexe</code> file by building a separate
486<code>.nexe</code> for each architecture, and using a <code>.nmf</code> manifest file to
487let the browser select the correct <code>.nexe</code> file. Note: the need to
488select a processor-specific <code>.nexe</code> goes away with Portable Native
489Client.</li>
490<li>If things still aren&#8217;t working, <a class="reference internal" href="/native-client/help.html"><em>ask for help</em></a>!</li>
491</ul>
[email protected]c3c19f12014-08-06 18:01:43492</section>
[email protected]bde3d5d2014-01-23 19:26:04493
494{{/partials.standard_nacl_article}}