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      2 
      3 <section id="frequently-asked-questions">
      4 <h1 id="frequently-asked-questions">Frequently Asked Questions</h1>
      5 <div class="contents local" id="contents" style="display: none">
      6 <ul class="small-gap">
      7 <li><p class="first"><a class="reference internal" href="#what-is-native-client-good-for" id="id3">What is Native Client Good For?</a></p>
      8 <ul class="small-gap">
      9 <li><a class="reference internal" href="#why-did-google-build-native-client" id="id4">Why did Google build Native Client?</a></li>
     10 <li><a class="reference internal" href="#when-should-i-use-native-client" id="id5">When should I use Native Client?</a></li>
     11 <li><a class="reference internal" href="#when-should-i-use-portable-native-client" id="id6">When should I use Portable Native Client?</a></li>
     12 <li><a class="reference internal" href="#how-fast-does-code-run-in-portable-native-client" id="id7">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="id8">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="id9">If I want direct access to the OS, should I use Native Client?</a></li>
     15 </ul>
     16 </li>
     17 <li><p class="first"><a class="reference internal" href="#development-environments-and-tools" id="id10">Development Environments and Tools</a></p>
     18 <ul class="small-gap">
     19 <li><a class="reference internal" href="#what-development-environment-and-development-operating-system-do-you-recommend" id="id11">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="id12">I&#8217;m not familiar with native development tools, can I still use the Native Client SDK?</a></li>
     21 </ul>
     22 </li>
     23 <li><p class="first"><a class="reference internal" href="#openness-and-supported-architectures-and-languages" id="id13">Openness, and Supported Architectures and Languages</a></p>
     24 <ul class="small-gap">
     25 <li><a class="reference internal" href="#is-native-client-open-is-it-a-standard" id="id14">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="id15">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="id16">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="#will-you-only-support-chrome-what-about-other-browsers" id="id17">Will 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="id18">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="id19">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="id20">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="id21">Can I use Native Client for 3D graphics?</a></li>
     33 <li><a class="reference internal" href="#does-native-client-support-concurrency-parallelism" id="id22">Does Native Client support concurrency/parallelism?</a></li>
     34 </ul>
     35 </li>
     36 <li><p class="first"><a class="reference internal" href="#coming-soon" id="id23">Coming Soon</a></p>
     37 <ul class="small-gap">
     38 <li><a class="reference internal" href="#do-native-client-modules-have-access-to-external-devices" id="id24">Do Native Client modules have access to external devices?</a></li>
     39 </ul>
     40 </li>
     41 <li><p class="first"><a class="reference internal" href="#security-and-privacy" id="id25">Security and Privacy</a></p>
     42 <ul class="small-gap">
     43 <li><a class="reference internal" href="#what-happens-to-my-data-when-i-use-native-client" id="id26">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="id27">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="id28">How does Google know that the safety measures in Native Client are sufficient?</a></li>
     46 </ul>
     47 </li>
     48 <li><p class="first"><a class="reference internal" href="#development" id="id29">Development</a></p>
     49 <ul class="small-gap">
     50 <li><a class="reference internal" href="#how-do-i-debug" id="id30">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="id31">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="id32">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="id33">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="id34">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="id35">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="id36">Do all the files in an application need to be served from the same domain?</a></li>
     57 </ul>
     58 </li>
     59 <li><p class="first"><a class="reference internal" href="#portability" id="id37">Portability</a></p>
     60 <ul class="small-gap">
     61 <li><a class="reference internal" href="#do-i-have-to-do-anything-special-to-make-my-application-run-on-different-operating-systems" id="id38">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="id39">How easy is it to port my existing native code to Native Client?</a></li>
     63 </ul>
     64 </li>
     65 <li><p class="first"><a class="reference internal" href="#troubleshooting" id="id40">Troubleshooting</a></p>
     66 <ul class="small-gap">
     67 <li><a class="reference internal" href="#my-pexe-isn-t-loading-help" id="id41">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="id42">My <code>.nexe</code> files never finish loading. What gives?</a></li>
     69 </ul>
     70 </li>
     71 </ul>
     72 
     73 </div><p>This document answers some frequently asked questions about Native
     74 Client (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>
     82 <section id="what-is-native-client-good-for">
     83 <h2 id="what-is-native-client-good-for">What is Native Client Good For?</h2>
     84 <section id="why-did-google-build-native-client">
     85 <h3 id="why-did-google-build-native-client">Why did Google build Native Client?</h3>
     86 <ul class="small-gap">
     87 <li><strong>Performance:</strong> Native Client modules run nearly as fast as native
     88 compiled code.</li>
     89 <li><strong>Security:</strong> Native Client lets users run native compiled code in the
     90 browser with the same level of security and privacy as traditional web
     91 applications.</li>
     92 <li><p class="first"><strong>Convenience:</strong></p>
     93 <ul class="small-gap">
     94 <li>Developers can leverage existing code, written in C/C++ or other
     95 languages, in their applications without forcing users to install a
     96 plugin.</li>
     97 <li>This code can interact with the embedding web page as part of an
     98 HTML and JavaScript web application, or it can be a self-contained
     99 and immersive experience.</li>
    100 </ul>
    101 </li>
    102 <li><p class="first"><strong>Portability:</strong> Native Client and Portable Native Client applications
    103 can execute on:</p>
    104 <ul class="small-gap">
    105 <li>The Windows, Mac, Linux or ChromeOS operating systems.</li>
    106 <li>Processors with the x86-32, x86-64, or ARM instruction set
    107 architectures. Native Client also has experimental support for MIPS.</li>
    108 </ul>
    109 </li>
    110 </ul>
    111 <p>Portable Native client further enhances the above:</p>
    112 <ul class="small-gap">
    113 <li><strong>Performance:</strong> Each PNaCl release brings with it more performance
    114 enhancements. Already-released applications get faster over time,
    115 conserving user&#8217;s battery.</li>
    116 <li><strong>Security:</strong> Users are kept secure with an ever-improving sandbox
    117 model which adapts to novel attacks, without affecting
    118 already-released applications.</li>
    119 <li><strong>Convenience:</strong> Developers only need to ship a single <code>.pexe</code> file,
    120 not one <code>.nexe</code> file per supported architecture.</li>
    121 <li><strong>Portability:</strong> Developers and users don&#8217;t need to worry about
    122 already-released applications not working on new hardware: PNaCl
    123 already supports all architectures NaCl does, and as PNaCl evolves it
    124 gains support for new processors and fully uses their capabilities.</li>
    125 </ul>
    126 <p>For more details, refer to the <a class="reference internal" href="/native-client/nacl-and-pnacl.html"><em>history behind and comparison of
    127 NaCl and PNaCl</em></a>.</p>
    128 </section><section id="when-should-i-use-native-client">
    129 <h3 id="when-should-i-use-native-client">When should I use Native Client?</h3>
    130 <p>The following are some typical use cases. For details, see the
    131 <a class="reference internal" href="/native-client/overview.html"><em>Technical Overview</em></a>.</p>
    132 <ul class="small-gap">
    133 <li>Porting existing software components for use in a web application.</li>
    134 <li>Porting legacy desktop applications.</li>
    135 <li>Handling browser-side encryption and decryption for an enterprise
    136 application.</li>
    137 <li>Handling multimedia for a web application.</li>
    138 <li>Handling various aspects of web-based games, including physics engines
    139 and AI.</li>
    140 </ul>
    141 <p>Native Client is a versatile technology; we expect that it will also be
    142 used in many other contexts outside of Chrome.</p>
    143 </section><section id="when-should-i-use-portable-native-client">
    144 <h3 id="when-should-i-use-portable-native-client">When should I use Portable Native Client?</h3>
    145 <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
    146 open web whereas NaCl only works on the Chrome Web Store.</p>
    147 </section><section id="how-fast-does-code-run-in-portable-native-client">
    148 <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
    150 the following overhead for optimized PNaCl compared to regular optimized
    151 LLVM:</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
    168 cases are likely to achieve better or worse performance than the above
    169 averages. For example floating-point heavy code usually exhibits much
    170 lower overheads whereas very branch-heavy code often performs worse.</p>
    171 <p>Note that PNaCl supports performance features that are often used in
    172 native 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>
    174 <p>For details, see:</p>
    175 <ul class="small-gap">
    176 <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>
    177 <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>
    178 </ul>
    179 <p>If your code isn&#8217;t performing as close to native speed as you&#8217;d expect,
    180 <a class="reference internal" href="/native-client/help.html"><em>let us know</em></a>!</p>
    181 </section><section id="why-use-portable-native-client-instead-of-technology-x">
    182 <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:
    184 Flash, Java, Silverlight, ActiveX, .NET, asm.js, etc...</p>
    185 <p>Different technologies have different strengths and weaknesses. In
    186 appropriate contexts, Portable Native Client can be faster, more secure,
    187 and/or more compatible across operating systems and architectures than
    188 other technologies.</p>
    189 <p>Portable Native Client complement other technologies by giving web
    190 developers a new capability: the ability to run fast, secure native code
    191 from a web browser in an architecture-independent way.</p>
    192 </section><section id="if-i-want-direct-access-to-the-os-should-i-use-native-client">
    193 <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>
    194 <p>No&#8212;Native Client does not provide direct access to the OS or devices,
    195 or otherwise bypass the JavaScript security model. For more information,
    196 see later sections of this FAQ.</p>
    197 </section></section><section id="development-environments-and-tools">
    198 <h2 id="development-environments-and-tools">Development Environments and Tools</h2>
    199 <section id="what-development-environment-and-development-operating-system-do-you-recommend">
    200 <h3 id="what-development-environment-and-development-operating-system-do-you-recommend">What development environment and development operating system do you recommend?</h3>
    201 <p>You can develop on Windows, Mac, or Linux, and the resulting Native
    202 Client or Portable Native Client application will run inside the Google
    203 Chrome browser on all those platforms as well as ChromeOS. You can also
    204 develop on ChromeOS with <a class="reference external" href="https://github.com/dnschneid/crouton">Crouton</a>, and we&#8217;re working on
    205 self-hosting a full development environment on Portable Native Client.</p>
    206 <p>Any editor+shell combination should work as well as IDEs like Eclipse,
    207 Visual 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>
    208 </section><section id="i-m-not-familiar-with-native-development-tools-can-i-still-use-the-native-client-sdk">
    209 <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>
    210 <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
    211 instructions</em></a> useful, and you can look at
    212 the code and Makefiles for the SDK examples to understand how the
    213 examples are built and run.</p>
    214 <p>You&#8217;ll need to learn how to use some tools (like GCC, LLVM, make,
    215 Eclipse, Visual Studio, or Xcode) before you can get very far with the
    216 SDK. Try seaching for an <a class="reference external" href="https://www.google.com/search?q=gcc+introduction">introduction to GCC</a>.</p>
    217 </section></section><section id="openness-and-supported-architectures-and-languages">
    218 <h2 id="openness-and-supported-architectures-and-languages">Openness, and Supported Architectures and Languages</h2>
    219 <section id="is-native-client-open-is-it-a-standard">
    220 <h3 id="is-native-client-open-is-it-a-standard">Is Native Client open? Is it a standard?</h3>
    221 <p>Native Client is completely open: the executable format is open and the
    222 <a class="reference external" href="nacl_project_">source code is open</a>. Right
    223 now the Native Client project is in its early stages, so it&#8217;s premature
    224 to consider Native Client for standardization.</p>
    225 <p>We consistenly try to document our design and implementation and hope to
    226 standardize Portable Native Client when it gains more traction. A good
    227 example is our <a class="reference internal" href="/native-client/reference/pnacl-bitcode-abi.html"><em>PNaCl bitcode reference manual</em></a>.</p>
    228 </section><section id="what-are-the-supported-instruction-set-architectures">
    229 <h3 id="what-are-the-supported-instruction-set-architectures">What are the supported instruction set architectures?</h3>
    230 <p>Portable Native Client uses an architecture-independent format (the
    231 <code>.pexe</code>) which can currently be translated to execute on processors
    232 with the x86-32, x86-64, and ARM instruction set architectures, as well
    233 as experimental support for MIPS. As new architectures come along and
    234 become popular we expect Portable Native Client to support them without
    235 developers having to recompile their code.</p>
    236 <p>Native Client can currently execute on the same architectures as
    237 Portable Native Client but is only supported on the Chrome Web
    238 Store. Native Client&#8217;s <code>.nexe</code> files are architecture-dependent and
    239 cannot adapt to new architectures without recompilation, we therefore
    240 deem them better suited to a web store than to the open web.</p>
    241 <p>With Portable Native Client we deliver a system that has comparable
    242 portability to JavaScript and can adapt to new instruction set
    243 architectures without requiring recompilation. The web is better when
    244 it&#8217;s platform-independent, and we&#8217;d like it to stay that way.</p>
    245 </section><section id="do-i-have-to-use-c-or-c-i-d-really-like-to-use-another-language">
    246 <span id="other-languages"></span><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>
    247 <p>Right now only C and C++ are supported directly by the toolchain in the
    248 SDK. C# and other languages in the .NET family are supported via the
    249 <a class="reference external" href="https://github.com/elijahtaylor/mono">Mono port</a> for Native
    250 Client. Moreover, there are several ongoing projects to support
    251 additional 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
    252 Ruby</a>)
    253 as well as to compile more languages to LLVM&#8217;s intermediate
    254 representation (e.g. support Haskell with <a class="reference external" href="http://www.haskell.org/ghc/docs/latest/html/users_guide/code-generators.html">GHC</a>
    255 or support Fortran with <a class="reference external" href="https://flang-gsoc.blogspot.ie/2013/09/end-of-gsoc-report.html">flang</a>), or
    256 transpile languages to C/C++ (source-to-source compilation).</p>
    257 <p>If you&#8217;re interested in getting other languages working, please contact the
    258 Native Client team by way of the <a class="reference external" href="https://groups.google.com/group/native-client-discuss">native-client-discuss mailing list</a>.</p>
    259 </section><section id="will-you-only-support-chrome-what-about-other-browsers">
    260 <h3 id="will-you-only-support-chrome-what-about-other-browsers">Will you only support Chrome? What about other browsers?</h3>
    261 <p>We aim to support multiple browsers. However, a number of features that
    262 we consider requirements for a production-quality system that keeps the
    263 user safe are difficult to implement without help from the
    264 browser. Specific examples are an out-of-process plugin architecture and
    265 appropriate interfaces for integrated 3D graphics. We have worked
    266 closely with Chromium developers to deliver these features and we are
    267 eager to collaborate with developers from other browsers.</p>
    268 </section><section id="what-s-the-difference-between-npapi-and-pepper">
    269 <h3 id="what-s-the-difference-between-npapi-and-pepper">What&#8217;s the difference between NPAPI and Pepper?</h3>
    270 <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
    271 lets Native Client modules communicate with the browser. Pepper supports
    272 various features that don&#8217;t have robust support in NPAPI, such as event
    273 handling, out-of-process plugins, and asynchronous interfaces. Native
    274 Client has transitioned from using NPAPI to using Pepper.</p>
    275 </section><section id="is-npapi-part-of-the-native-client-sdk">
    276 <h3 id="is-npapi-part-of-the-native-client-sdk">Is NPAPI part of the Native Client SDK?</h3>
    277 <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
    278 Chrome</a>.</p>
    279 </section><section id="does-native-client-support-simd-vector-instructions">
    280 <h3 id="does-native-client-support-simd-vector-instructions">Does Native Client support SIMD vector instructions?</h3>
    281 <p>Native Client currently supports SSE on x86 and NEON on ARM. Support for
    282 AVX on x86 is under way.</p>
    283 <p>Portable Native Client supports portable SIMD vectors, as detailed in
    284 <a class="reference internal" href="/native-client/reference/pnacl-c-cpp-language-support.html#portable-simd-vectors"><em>Portable SIMD Vectors</em></a>.</p>
    285 </section><section id="can-i-use-native-client-for-3d-graphics">
    286 <h3 id="can-i-use-native-client-for-3d-graphics">Can I use Native Client for 3D graphics?</h3>
    287 <p>Yes. Native Client supports <a class="reference external" href="https://www.khronos.org/opengles/">OpenGL ES 2.0</a>.</p>
    288 <p>To alert the user regarding their hardware platform&#8217;s 3D feature set
    289 before loading a large NaCl application, see <a class="reference internal" href="/native-client/devguide/coding/3D-graphics.html"><em>Vetting the driver in
    290 Javascript</em></a>.</p>
    291 <p>Some GL extensions are exposed to Native Client applications, see the
    292 <a class="reference external" href="https://src.chromium.org/viewvc/chrome/trunk/src/ppapi/lib/gl/gles2/gles2.c">GLES2 file</a>.
    293 This file is part of the GL wrapper supplied by the library
    294 <code>ppapi_gles2</code> which you&#8217;ll want to include in your project.  In most
    295 cases extensions map to extensions available on other platforms, or
    296 differ very slightly (if they differ, the extension is usually CHROMIUM
    297 or ANGLE instead of EXT).</p>
    298 </section><section id="does-native-client-support-concurrency-parallelism">
    299 <h3 id="does-native-client-support-concurrency-parallelism">Does Native Client support concurrency/parallelism?</h3>
    300 <p>Native Client and Portable Native Client both support pthreads,
    301 C11/C++11 threads, and low-level synchronization primitives (mutex,
    302 barriers, atomic read/modify/write, compare-and-exchange, etc...), thus
    303 allowing your Native Client application to utilize several CPU cores.
    304 Note that this allows you to modify datastructures concurrently without
    305 needing to copy them, which is often a limitation of shared-nothing
    306 systems. 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>
    307 <p>Native Client doesn&#8217;t support HTML5 Web Workers directly but can
    308 interact with JavaScript code which does.</p>
    309 </section></section><section id="coming-soon">
    310 <h2 id="coming-soon">Coming Soon</h2>
    311 <section id="do-native-client-modules-have-access-to-external-devices">
    312 <h3 id="do-native-client-modules-have-access-to-external-devices">Do Native Client modules have access to external devices?</h3>
    313 <p>At this time Native Client modules do not have access to serial ports,
    314 camera devices, or microphones: Native Client can only use native
    315 resources that today&#8217;s browsers can access. However, we intend to
    316 recommend such features to the standards bodies and piggyback on their
    317 efforts to make these resources available inside the browser.</p>
    318 <p>You can generally think of Pepper as the C/C++ bindings to the
    319 capabilities of HTML5. The goal is for Pepper and JavaScript to evolve
    320 together and stay on par with each other with respect to features and
    321 capabilities.</p>
    322 </section></section><section id="security-and-privacy">
    323 <h2 id="security-and-privacy">Security and Privacy</h2>
    324 <section id="what-happens-to-my-data-when-i-use-native-client">
    325 <h3 id="what-happens-to-my-data-when-i-use-native-client">What happens to my data when I use Native Client?</h3>
    326 <p>Users can opt-in to sending usage statistics and crash information in
    327 Chrome, which includes usage statistics and crash information about
    328 Native Client. Crashes in your code won&#8217;t otherwise send your
    329 information to Google: Google counts the number of such crashes, but
    330 does so anonymously without sending your application&#8217;s data or its debug
    331 information.</p>
    332 <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
    333 Chrome privacy policy</a> and the <a class="reference external" href="https://www.google.com/chrome/intl/en/eula_text.html">Google
    334 Chrome Terms of Service</a>.</p>
    335 </section><section id="how-does-native-client-prevent-sandboxed-code-from-doing-bad-things">
    336 <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>
    337 <p>Native Client&#8217;s sandbox works by validating the untrusted code (the
    338 compiled Native Client module) before running it. The validator checks
    339 the following:</p>
    340 <ul class="small-gap">
    341 <li><strong>Data integrity:</strong> No loads or stores are permitted outside of the
    342 data sandbox. In particular this means that once loaded into memory,
    343 the binary is not writable. This is enforced by operating system
    344 protection mechanisms. While new instructions can be inserted at
    345 runtime to support things like JIT compilers, such instructions will
    346 be subject to runtime verification according to the following
    347 constraints before they are executed.</li>
    348 <li><strong>No unsafe instructions:</strong> The validator ensures that the Native
    349 Client application does not contain any unsafe instructions. Examples
    350 of unsafe instructions are <code>syscall</code>, <code>int</code>, and <code>lds</code>.</li>
    351 <li><strong>Control flow integrity:</strong> The validator ensures that all direct and
    352 indirect branches target a safe instruction.</li>
    353 </ul>
    354 <p>The beauty of the Native Client sandbox is in reducing &#8220;safe&#8221; code to a
    355 few simple rules that can be verified by a small trusted validator: the
    356 compiler isn&#8217;t trusted. The same applies to Portable Native Client where
    357 even the <code>.pexe</code> to <code>.nexe</code> translator, a simplified compiler
    358 backend, isn&#8217;t trusted: it is validated before executing, and so is its
    359 output.</p>
    360 <p>In addition to static analysis of untrusted code, the Native Client
    361 runtime also includes an outer sandbox that mediates system calls. For
    362 more details about both sandboxes, see <a class="reference external" href="http://research.google.com/pubs/pub34913.html">Native Client: A Sandbox for
    363 Portable, Untrusted x86 Code</a>
    364 (PDF).</p>
    365 </section><section id="how-does-google-know-that-the-safety-measures-in-native-client-are-sufficient">
    366 <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>
    367 <p>Google has taken several steps to ensure that Native Client&#8217;s security
    368 works, including:</p>
    369 <ul class="small-gap">
    370 <li>Open source, peer-reviewed papers describing the design.</li>
    371 <li>A <a class="reference internal" href="/native-client/community/security-contest/index.html"><em>security contest</em></a>.</li>
    372 <li>Multiple internal and external security reviews.</li>
    373 <li>The ongoing vigilance of our engineering and developer community.</li>
    374 </ul>
    375 <p>Google is committed to making Native Client safer than JavaScript and
    376 other popular browser technologies. If you have suggestions for security
    377 improvements, let the team know, by way of the <a class="reference external" href="https://groups.google.com/group/native-client-discuss">native-client-discuss
    378 mailing list</a>.</p>
    379 </section></section><section id="development">
    380 <h2 id="development">Development</h2>
    381 <section id="how-do-i-debug">
    382 <h3 id="how-do-i-debug">How do I debug?</h3>
    383 <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
    384 debug Native Client modules with some <a class="reference internal" href="/native-client/devguide/devcycle/debugging.html"><em>alternative approaches</em></a>.</p>
    385 </section><section id="how-do-i-build-x86-32-x86-64-or-arm-nexes">
    386 <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>
    387 <p>By default, the applications in the <code>/examples</code> folder create
    388 architecture-independent <code>.pexe</code> for Portable Native Client. To
    389 generate a <code>.nexe</code> targetting one specific architecture using the
    390 Native Client or Portable Native Client toolchains, see the
    391 <a class="reference internal" href="/native-client/devguide/devcycle/building.html"><em>Building instructions</em></a>.</p>
    392 </section><section id="how-can-my-web-application-determine-which-nexe-to-load">
    393 <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>
    394 <p>Your application does not need to make the decision of loading an
    395 x86-32, x86-64 or ARM <code>.nexe</code> explicitly&#8212;the Native Client runtime
    396 examines a manifest file (<code>.nmf</code>) to pick the right <code>.nexe</code> file for
    397 a given user. You can generate a manifest file using a Python script
    398 that&#8217;s included in the SDK (see the <code>Makefile</code> in any of the SDK
    399 examples for an illustration of how to do so). Your HTML file specifies
    400 the manifest filename in the <code>src</code> attribute of the <code>&lt;embed&gt;</code>
    401 tag. You can see the way the pieces fit together by examining the
    402 examples included in the SDK.</p>
    403 </section><section id="is-it-possible-to-build-a-native-client-module-with-just-plain-c-not-c">
    404 <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>
    405 <p>Yes. See the <code>&quot;Hello, World!&quot;</code> in C example in the SDK under
    406 <code>examples/tutorial/using_ppapi_simple/</code>, or the Game of Life example
    407 under <code>examples/demo/life/life.c</code>.</p>
    408 </section><section id="what-unix-system-calls-can-i-make-through-native-client">
    409 <h3 id="what-unix-system-calls-can-i-make-through-native-client">What UNIX system calls can I make through Native Client?</h3>
    410 <p>Native Client doesn&#8217;t directly expose any system calls from the host OS
    411 because of the inherent security risks and because the resulting
    412 application would not be portable across operating systems. Instead,
    413 Native Client provides portable cross-OS abstractions wrapping or
    414 proxying OS functionality or emulating UNIX system calls. For example,
    415 Native Client provides an <code>mmap()</code> system call that behaves much like
    416 the standard UNIX <code>mmap()</code> system call.</p>
    417 </section><section id="is-my-favorite-third-party-library-available-for-native-client">
    418 <h3 id="is-my-favorite-third-party-library-available-for-native-client">Is my favorite third-party library available for Native Client?</h3>
    419 <p>Google has ported several third-party libraries to Native Client; such
    420 libraries are available in the <a class="reference external" href="https://code.google.com/p/naclports">naclports</a> project. We encourage you to
    421 contribute libraries to naclports, and/or to host your own ported
    422 libraries, and to <a class="reference external" href="https://groups.google.com/group/native-client-discuss">let the team know about it</a> when you do.</p>
    423 </section><section id="do-all-the-files-in-an-application-need-to-be-served-from-the-same-domain">
    424 <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>
    425 <p>The <code>.nmf</code>, and <code>.nexe</code> or <code>.pexe</code> files must either be served from the
    426 same origin as the embedding page or an origin that has been configured
    427 correctly using <a class="reference external" href="http://en.wikipedia.org/wiki/Cross-origin_resource_sharing">CORS</a>.</p>
    428 <p>For applications installed from the Chrome Web Store the Web Store manifest
    429 must include the correct, verified domain of the embedding page.</p>
    430 </section></section><section id="portability">
    431 <h2 id="portability">Portability</h2>
    432 <section id="do-i-have-to-do-anything-special-to-make-my-application-run-on-different-operating-systems">
    433 <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>
    434 <p>No. Native Client and Portable Native Client applications run without
    435 modification on all supported operating systems.</p>
    436 <p>However, to run on different instruction set architectures (such as
    437 x86-32, x86-64 or ARM), you currently have to either:</p>
    438 <ul class="small-gap">
    439 <li>Use Portable Native Client.</li>
    440 <li>Build and supply a separate <code>.nexe</code> file for each architecture, and
    441 make them available on the Chrome Web Store. See <a class="reference internal" href="/native-client/devguide/devcycle/building.html"><em>target
    442 architectures</em></a> for details about which
    443 <code>.nexe</code> files will run on which architectures.</li>
    444 </ul>
    445 </section><section id="how-easy-is-it-to-port-my-existing-native-code-to-native-client">
    446 <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>
    447 <p>In most cases you won&#8217;t have to rewrite much, if any, code. The Native
    448 Client-specific tools, such as <code>pnacl-clang++</code> or <code>x86_64-nacl-g++</code>,
    449 take care of most of the necessary changes. You may need to make some
    450 changes to your operating system calls and interactions with external
    451 devices to work with the web. Porting existing Linux libraries is
    452 generally straightforward, with large libraries often requiring no
    453 source change.</p>
    454 <p>The following kinds of code may be more challenging to port:</p>
    455 <ul class="small-gap">
    456 <li>Code that does direct TCP/IP or UDP networking. For security reasons
    457 these APIs are only available to packaged applications, not on the
    458 open web, after asking for the appropriate permissions. Native Client
    459 is otherwise restricted to the networking APIs available in the
    460 browser.</li>
    461 <li>Code that creates processes, including UNIX forks. Creating processes
    462 is not supported for security reasons. However, threads are supported.</li>
    463 <li>Code that needs to do local file I/O. Native Client is restricted to
    464 accessing URLs and to local storage in the browser (the Pepper file I/O API
    465 has access to the same per-application storage that JavaScript has via Local
    466 Storage). HTML5 File System can be used, among others. For POSIX compatabiliy
    467 the Native Client SDK includes a library called nacl_io which allows the
    468 application to interact with all these types of files via standard POSIX I/O
    469 functions (e.g. open/fopen/read/write/...). See <a class="reference internal" href="/native-client/devguide/coding/nacl_io.html"><em>Using NaCl I/O</em></a> for more details.</li>
    470 </ul>
    471 </section></section><section id="troubleshooting">
    472 <span id="faq-troubleshooting"></span><h2 id="troubleshooting"><span id="faq-troubleshooting"></span>Troubleshooting</h2>
    473 <section id="my-pexe-isn-t-loading-help">
    474 <h3 id="my-pexe-isn-t-loading-help">My <code>.pexe</code> isn&#8217;t loading, help!</h3>
    475 <ul class="small-gap">
    476 <li>You must use Google Chrome version 31 or greater for Portable Native
    477 Client. Make sure you have Portable Native Client installed in
    478 <code>about:nacl</code>; if not open <code>about:components</code> and &#8220;Check for
    479 update&#8221; for PNaCl.</li>
    480 <li>PNaCl <code>.pexe</code> must be compiled with pepper_31 SDK or higher (earlier
    481 SDK versions had experimental support for PNaCl, now deprecated).</li>
    482 <li>Your application can verify that Portable Native Client is supported
    483 in JavaScript with <code>navigator.mimeTypes['application/x-pnacl'] !==
    484 undefined</code>. This is preferred over checking the Chrome version.</li>
    485 </ul>
    486 </section><section id="my-nexe-files-never-finish-loading-what-gives">
    487 <h3 id="my-nexe-files-never-finish-loading-what-gives">My <code>.nexe</code> files never finish loading. What gives?</h3>
    488 <p>Here are ways to resolve some common problems that can prevent loading:</p>
    489 <ul class="small-gap">
    490 <li>You must use Google Chrome version 14 or greater for Native Client.</li>
    491 <li>If you haven&#8217;t already done so, enable the Native Client flag in
    492 Google Chrome. Type <code>about:flags</code> in the Chrome address bar, scroll
    493 down to &#8220;Native Client&#8221;, click the &#8220;Enable&#8221; link, scroll down to the
    494 bottom of the page, and click the &#8220;Relaunch Now&#8221; button (all browser
    495 windows will restart).</li>
    496 <li>Verify that the Native Client plugin is enabled in Google Chrome. Type
    497 <code>about:plugins</code> in the Chrome address bar, scroll down to &#8220;Native
    498 Client&#8221;, and click the &#8220;Enable&#8221; link. (You do not need to relaunch
    499 Chrome after you enable the Native Client plugin).</li>
    500 <li>Make sure that the <code>.nexe</code> files are being served from a web
    501 server. Native Client uses the same-origin security policy, which
    502 means that modules will not load in pages opened with the <code>file://</code>
    503 protocol. In particular, you can&#8217;t run the examples in the SDK by
    504 simply dragging the HTML files from the desktop into the browser. See
    505 <a class="reference internal" href="/native-client/devguide/devcycle/running.html"><em>Running Native Client Applications</em></a>
    506 for instructions on how to run the httpd.py mini-server included in
    507 the SDK.</li>
    508 <li>The <code>.nexe</code> files must have been compiled using SDK version 0.5 or
    509 greater.</li>
    510 <li>You must load the correct <code>.nexe</code> file for your machine&#8217;s specific
    511 instruction set architecture (x86-32, x86-64 or ARM). You can ensure
    512 you&#8217;re loading the correct <code>.nexe</code> file by building a separate
    513 <code>.nexe</code> for each architecture, and using a <code>.nmf</code> manifest file to
    514 let the browser select the correct <code>.nexe</code> file. Note: the need to
    515 select a processor-specific <code>.nexe</code> goes away with Portable Native
    516 Client.</li>
    517 <li>If things still aren&#8217;t working, <a class="reference internal" href="/native-client/help.html"><em>ask for help</em></a>!</li>
    518 </ul>
    519 </section></section></section>
    520 
    521 {{/partials.standard_nacl_article}}
    522