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Issue 476793002: Per P0 reqs add launch pts + make download obvious. Also misc cpy edits. (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: Created 6 years, 4 months ago
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1 {{+bindTo:partials.standard_nacl_article}} 1 {{+bindTo:partials.standard_nacl_article}}
2 2
3 <section id="nacl-and-pnacl"> 3 <section id="nacl-and-pnacl">
4 <span id="id1"></span><h1 id="nacl-and-pnacl"><span id="id1"></span>NaCl and PNa Cl</h1> 4 <span id="id1"></span><h1 id="nacl-and-pnacl"><span id="id1"></span>NaCl and PNa Cl</h1>
5 <p>This document describes the differences between <strong>Native Client</strong > and 5 <p>This document describes the differences between <strong>Native Client</strong > and
6 <strong>Portable Native Client</strong>, and provides recommendations for when t o use each.</p> 6 <strong>Portable Native Client</strong>, and provides recommendations for when t o use each.</p>
7 <div class="contents local" id="contents" style="display: none"> 7 <div class="contents local" id="contents" style="display: none">
8 <ul class="small-gap"> 8 <ul class="small-gap">
9 <li><a class="reference internal" href="#native-client-nacl" id="id3">Native Cli ent (NaCl)</a></li> 9 <li><a class="reference internal" href="#native-client-nacl" id="id3">Native Cli ent (NaCl)</a></li>
10 <li><a class="reference internal" href="#portable-native-client-pnacl" id="id4"> Portable Native Client (PNaCl)</a></li> 10 <li><a class="reference internal" href="#portable-native-client-pnacl" id="id4"> Portable Native Client (PNaCl)</a></li>
11 <li><a class="reference internal" href="#when-to-use-pnacl" id="id5">When to use PNaCl</a></li> 11 <li><a class="reference internal" href="#when-to-use-pnacl" id="id5">When to use PNaCl</a></li>
12 <li><a class="reference internal" href="#when-to-use-nacl" id="id6">When to use NaCl</a></li> 12 <li><a class="reference internal" href="#when-to-use-nacl" id="id6">When to use NaCl</a></li>
13 </ul> 13 </ul>
14 14
15 </div><section id="native-client-nacl"> 15 </div><section id="native-client-nacl">
16 <h2 id="native-client-nacl">Native Client (NaCl)</h2> 16 <h2 id="native-client-nacl">Native Client (NaCl)</h2>
17 <p>Native Client enables the execution of native code securely inside web 17 <p>Native Client enables the execution of native code securely inside web
18 applications through the use of advanced <a class="reference external" href="/na tive-client/community/talks#research">Software Fault Isolation (SFI) 18 applications through the use of advanced <a class="reference external" href="/na tive-client/community/talks#research">Software Fault Isolation (SFI)
19 techniques</a>. Since its launch in 19 techniques</a>. Since its launch in
20 2011, Native Client has provided developers with the ability to harness a 20 2011, Native Client has provided developers with the ability to harness a
21 client machine&#8217;s computational power to a much fuller extent than traditio nal 21 client machine&#8217;s computational power to a much fuller extent than traditio nal
22 web technologies, by running compiled C and C++ code at near-native speeds and 22 web technologies, by running compiled C and C++ code at near-native speeds and
23 taking advantage of multiple cores with shared memory.</p> 23 taking advantage of multiple cores with shared memory.</p>
24 <p>While Native Client provides operating system independence, it requires 24 <p>While Native Client provides operating system independence, it requires
25 developers to generate architecture-specific executable modules 25 developers to generate architecture-specific executable
26 (<strong>nexe</strong> modules) for each hardware platform. This is not only inc onvenient 26 (<strong>nexe</strong>) modules for each hardware platform. This is not only inc onvenient
27 for developers, but architecture-specific machine code is not portable and thus 27 for developers, but architecture-specific machine code is not portable and thus
28 not well-suited for the open web. The traditional method of application 28 not well-suited for the open web. The traditional method of application
29 distribution on the web is through a self-contained bundle of HTML, CSS, 29 distribution on the web is through a self-contained bundle of HTML, CSS,
30 JavaScript, and other resources (images, etc.) that can be hosted on a server 30 JavaScript, and other resources (images, etc.) that can be hosted on a server
31 and run inside a web browser. With this type of distribution, a website 31 and run inside a web browser. With this type of distribution, a website
32 created today should still work years later, on all platforms. 32 created today should still work years later, on all platforms.
33 Architecture-specific executables are clearly not a good fit for distribution 33 Architecture-specific executables are clearly not a good fit for distribution
34 on the web. As a consequence, Native Client has been restricted to 34 on the web. As a consequence, Native Client has been restricted to
35 applications and browser extensions that are installed through the 35 applications and browser extensions that are installed through the
36 Chrome Web Store.</p> 36 Chrome Web Store.</p>
37 </section><section id="portable-native-client-pnacl"> 37 </section><section id="portable-native-client-pnacl">
38 <h2 id="portable-native-client-pnacl">Portable Native Client (PNaCl)</h2> 38 <h2 id="portable-native-client-pnacl">Portable Native Client (PNaCl)</h2>
39 <p>PNaCl solves the portability problem by splitting the compilation process 39 <p>PNaCl solves the portability problem by splitting the compilation process
40 into two parts:</p> 40 into two parts:</p>
41 <ol class="arabic simple"> 41 <ol class="arabic simple">
42 <li>compiling the source code to a portable bitcode format, and</li> 42 <li>compiling the source code to a portable bitcode format, and</li>
43 <li>translating the bitcode to a host-specific executable.</li> 43 <li>translating the bitcode to a host-specific executable just before execution. </li>
44 </ol> 44 </ol>
45 <p>PNaCl enables developers 45 <p>PNaCl enables developers to distribute <strong>portable executables</strong> (<strong>pexe</strong>)
46 to distribute <strong>portable executables</strong> (<strong>pexe</strong> modul es) that the hosting 46 modules that the hosting environment (in other words, the Chrome browser) can
47 environment (e.g., the Chrome browser) can translate to native code before 47 translate to native code before executing. This portability aligns Native Client
48 executing. This portability aligns Native Client with existing open web 48 with existing open web technologies such as JavaScript. A developer can
49 technologies such as JavaScript: A developer can distribute a <strong>pexe</stro ng> 49 distribute a <strong>pexe</strong> as part of an application (along with HTML, C SS, and
50 as part of an application (along with HTML, CSS, and JavaScript), 50 JavaScript), and the user&#8217;s machine is simply able to run it.</p>
51 and the user&#8217;s machine is simply able to run it.</p>
52 <p>With PNaCl, a developer generates a single <strong>pexe</strong> from source code, 51 <p>With PNaCl, a developer generates a single <strong>pexe</strong> from source code,
53 rather than multiple platform-specific nexes. The <strong>pexe</strong> provides both 52 rather than multiple platform-specific nexes. The <strong>pexe</strong> provides both
54 architecture- and OS-independence. Since the <strong>pexe</strong> uses an abstr act, 53 architecture- and OS-independence. Since the <strong>pexe</strong> uses an abstr act,
55 architecture-independent format, it does not suffer from the portability 54 architecture-independent format, it does not suffer from the portability
56 problem described above. Future versions of hosting environments should 55 problem described above. Future versions of hosting environments should
57 have no problem executing the <strong>pexe</strong>, even on new architectures. 56 have no problem executing the <strong>pexe</strong>, even on new architectures.
58 Moreover, if an existing architecture is subsequently enhanced, the 57 Moreover, if an existing architecture is subsequently enhanced, the
59 <strong>pexe</strong> doesn&#8217;t even have to be recompiled&#8212;in some cas es the 58 <strong>pexe</strong> doesn&#8217;t even have to be recompiled. In some cases th e
60 client-side translation will automatically be able to take advantage of 59 client-side translation will automatically be able to take advantage of
61 the new capabilities.</p> 60 the new capabilities. A <strong>pexe</strong> module can be part of any web
62 <p><strong>In short, PNaCl combines the portability of existing web technologies with 61 application. It does not have to be distributed through the Chrome Web
63 the performance and security benefits of Native Client.</strong></p> 62 Store. In short, PNaCl combines the portability of existing web technologies
64 <p>With the advent of PNaCl, the distribution restriction of Native Client 63 with the performance and security benefits of Native Client.</p>
65 can be lifted. Specifically, a <strong>pexe</strong> module can be part of any w eb
66 application&#8212;it does not have to be distributed through the Chrome Web
67 Store.</p>
68 <p>PNaCl is a new technology, and as such it still has a few limitations 64 <p>PNaCl is a new technology, and as such it still has a few limitations
69 as compared to NaCl. These limitations are described below.</p> 65 as compared to NaCl. These limitations are described below.</p>
70 </section><section id="when-to-use-pnacl"> 66 </section><section id="when-to-use-pnacl">
71 <h2 id="when-to-use-pnacl">When to use PNaCl</h2> 67 <h2 id="when-to-use-pnacl">When to use PNaCl</h2>
72 <p>PNaCl is the preferred toolchain for Native Client, and the only way to deplo y 68 <p>PNaCl is the preferred toolchain for Native Client, and the only way to deplo y
73 Native Client modules on the open web. Unless your project is subject to one 69 Native Client modules on the open web. Unless your project is subject to one
74 of the narrow limitations described below 70 of the narrow limitations described below
75 (see <a class="reference internal" href="#when-to-use-nacl"><em>When to use NaCl </em></a>), you should use PNaCl.</p> 71 (see <a class="reference internal" href="#when-to-use-nacl"><em>When to use NaCl </em></a>), you should use PNaCl.</p>
76 <p>Beginning with version 31, the Chrome browser supports translation of 72 <p>Beginning with version 31, the Chrome browser supports translation of
77 <strong>pexe</strong> modules and their use in web applications, without requiri ng 73 <strong>pexe</strong> modules and their use in web applications, without requiri ng
78 any installation (either of a browser plugin or of the applications 74 any installation (either of a browser plugin or of the applications
79 themselves). Native Client and PNaCl are open-source technologies, and 75 themselves). Native Client and PNaCl are open-source technologies, and
80 our hope is that they will be added to other hosting platforms in the 76 our hope is that they will be added to other hosting platforms in the
81 future.</p> 77 future.</p>
82 <p>If controlled distribution through the Chrome Web Store is an important part 78 <p>If controlled distribution through the Chrome Web Store is an important part
83 of your product plan, the benefits of PNaCl are less critical for you. But 79 of your product plan, the benefits of PNaCl are less critical for you. But
84 you can still use the PNaCl toolchain and distribute your application 80 you can still use the PNaCl toolchain and distribute your application
85 through the Chrome Web Store, and thereby take advantage of the 81 through the Chrome Web Store, and thereby take advantage of the
86 conveniences of PNaCl, such as not having to explicitly compile your application 82 conveniences of PNaCl, such as not having to explicitly compile your application
87 for all supported architectures.</p> 83 for all supported architectures.</p>
88 </section><section id="when-to-use-nacl"> 84 </section><section id="when-to-use-nacl">
89 <span id="id2"></span><h2 id="when-to-use-nacl"><span id="id2"></span>When to us e NaCl</h2> 85 <span id="id2"></span><h2 id="when-to-use-nacl"><span id="id2"></span>When to us e NaCl</h2>
90 <p>The limitations below apply to the current release of PNaCl. If any of 86 <p>The limitations below apply to the current release of PNaCl. If any of
91 these limitations are critical for your application, you should use 87 these limitations are critical for your application, you should use
92 non-portable NaCl:</p> 88 non-portable NaCl:</p>
93 <ul class="small-gap"> 89 <ul class="small-gap">
94 <li>By its nature, PNaCl does not support architecture-specific 90 <li>PNaCl does not support architecture-specific
95 instructions in an application (i.e., inline assembly), but tries to 91 instructions in an application (i.e., inline assembly), but tries to
96 offer high-performance portable equivalents. One such example is 92 offer high-performance portable equivalents. One such example is
97 PNaCl&#8217;s <a class="reference internal" href="/native-client/reference/pnacl -c-cpp-language-support.html#portable-simd-vectors"><em>Portable SIMD Vectors</e m></a>.</li> 93 PNaCl&#8217;s <a class="reference internal" href="/native-client/reference/pnacl -c-cpp-language-support.html#portable-simd-vectors"><em>Portable SIMD Vectors</e m></a>.</li>
98 <li>Currently PNaCl only supports static linking with the <code>newlib</code> 94 <li>PNaCl only supports static linking with the <code>newlib</code>
99 C standard library (the Native Client SDK provides a PNaCl port of 95 C standard library (the Native Client SDK provides a PNaCl port of
100 <code>newlib</code>). Dynamic linking and <code>glibc</code> are not yet support ed. 96 <code>newlib</code>). Dynamic linking and <code>glibc</code> are not yet support ed.
101 Work is under way to enable dynamic linking in future versions of PNaCl.</li> 97 Work is under way to enable dynamic linking in future versions of PNaCl.</li>
102 <li>In the initial release, PNaCl does not support some GNU extensions 98 <li>PNaCl does not support some GNU extensions
103 like taking the address of a label for computed <code>goto</code>, or nested 99 like taking the address of a label for computed <code>goto</code>, or nested
104 functions.</li> 100 functions.</li>
105 </ul> 101 </ul>
106 </section></section> 102 </section></section>
107 103
108 {{/partials.standard_nacl_article}} 104 {{/partials.standard_nacl_article}}
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