1page.title=Namespaces for Native Libraries 2@jd:body 3 4<!-- 5 Copyright 2016 The Android Open Source Project 6 7 Licensed under the Apache License, Version 2.0 (the "License"); 8 you may not use this file except in compliance with the License. 9 You may obtain a copy of the License at 10 11 http://www.apache.org/licenses/LICENSE-2.0 12 13 Unless required by applicable law or agreed to in writing, software 14 distributed under the License is distributed on an "AS IS" BASIS, 15 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 See the License for the specific language governing permissions and 17 limitations under the License. 18--> 19 20<div id="qv-wrapper"> 21 <div id="qv"> 22 <h2>In this document</h2> 23 <ol id="auto-toc"> 24 </ol> 25 </div> 26</div> 27 28<p> 29Android 7.0 introduces namespaces for native libraries to limit internal API 30visibility and resolve situations when apps accidentally end up using platform 31libraries instead of their own. See the <a 32href="http://android-developers.blogspot.com/2016/06/improving-stability-with-private-cc.html">Improving 33Stability with Private C/C++ Symbol Restrictions in Android 7.0</a> Android 34Developers blog post</a> for application-specific changes. 35</p> 36 37<h2 id="architecture">Architecture</h2> 38 39<p> 40The change separates system libraries from application libraries and makes it 41hard to use internal system libraries by accident (and vice versa). 42</p> 43 44<img src="images/namespace-libraries.png" alt="Namespaces for native libraries" width="466" id="namespace-libraries" /> 45<p class="img-caption"> 46 <strong>Figure 1.</strong> Namespaces for native libraries 47</p> 48 49<p> 50Namespaces for native libraries prevent apps from using private-platform native 51APIs (as was done with OpenSSL). It also removes situations where apps 52accidentally end up using platform libraries instead of their own (as witnessed 53with <code>libpng</code>). 54</p> 55 56<h2 id="adding-additional-native-libraries">Adding additional native 57libraries</h2> 58 59<p> 60In addition to standard public native libraries, vendors may choose to provide 61additional native libraries accessible to apps by putting them under the 62<code>/vendor</code> library folder (/vendor/lib for 32 bit libraries and, 63/vendor/lib64 for 64 bit) and listing them in: 64<code>/vendor/etc/public.libraries.txt</code> 65</p> 66 67<h2 id="updating-app-non-public">Updating apps to not use non-public native libraries</h2> 68 69<p> 70This feature is enabled only for applications targeting SDK version 24 or later; 71for backward compatibility, see <a 72href="http://android-developers.blogspot.com/2016/06/improving-stability-with-private-cc.html">Table 731. What to expect if your app is linking against private native libraries</a>. 74The list of Android native libraries accessible to apps (also know as 75public native libraries) is listed in CDD section 3.1.1. Apps targeting 24 or 76later and using any non-public libraries should be updated. Please see <a 77href="https://developer.android.com/preview/behavior-changes.html#ndk">NDK Apps 78Linking to Platform Libraries </a> for more details. 79</p> 80
