1# C++ Support<a name="EN-US_TOPIC_0000001079036442"></a> 2 3- [Basic Concepts](#section11374125415814) 4- [Working Principles](#section189351319134418) 5- [Development Guidelines](#section166302407911) 6 - [Available APIs](#section1881825119919) 7 - [How to Develop](#section76371145108) 8 - [Development Example](#section994427141111) 9 10 11## Basic Concepts<a name="section11374125415814"></a> 12 13As one of the most widely used programming languages, C++ supports features, such as classes, encapsulation, and overloading. It is an object-oriented programming language developed based on the C language. 14 15## Working Principles<a name="section189351319134418"></a> 16 17The compiler supports C++ code identification. The system calls the constructors of global objects to perform initialization operations. 18 19## Development Guidelines<a name="section166302407911"></a> 20 21### Available APIs<a name="section1881825119919"></a> 22 23**Table 1** APIs supported by C++ 24 25<a name="table14277123518139"></a> 26<table><thead align="left"><tr id="row152771935131315"><th class="cellrowborder" valign="top" width="23.792379237923793%" id="mcps1.2.4.1.1"><p id="p1127733591316"><a name="p1127733591316"></a><a name="p1127733591316"></a>Category</p> 27</th> 28<th class="cellrowborder" valign="top" width="33.02330233023302%" id="mcps1.2.4.1.2"><p id="p22771357138"><a name="p22771357138"></a><a name="p22771357138"></a>API</p> 29</th> 30<th class="cellrowborder" valign="top" width="43.18431843184319%" id="mcps1.2.4.1.3"><p id="p327714358130"><a name="p327714358130"></a><a name="p327714358130"></a>Description</p> 31</th> 32</tr> 33</thead> 34<tbody><tr id="row119525513581"><td class="cellrowborder" valign="top" width="23.792379237923793%" headers="mcps1.2.4.1.1 "><p id="p2099535514346"><a name="p2099535514346"></a><a name="p2099535514346"></a>Prerequisites for using C++ features</p> 35</td> 36<td class="cellrowborder" valign="top" width="33.02330233023302%" headers="mcps1.2.4.1.2 "><p id="p3155620345"><a name="p3155620345"></a><a name="p3155620345"></a>LOS_CppSystemInit</p> 37</td> 38<td class="cellrowborder" valign="top" width="43.18431843184319%" headers="mcps1.2.4.1.3 "><p id="p4616566343"><a name="p4616566343"></a><a name="p4616566343"></a>Initializes C++ constructors.</p> 39</td> 40</tr> 41</tbody> 42</table> 43 44### How to Develop<a name="section76371145108"></a> 45 46Before using C++ features, you need to call **LOS\_CppSystemInit** to initialize C++ constructors. The initialized constructors are stored in the **init\_array** section, and the section range is passed by the variables **\_\_init\_array\_start\_\_** and **\_\_init\_array\_end\_\_**. 47 48**Table 2** Parameter description 49 50<a name="table71191652173718"></a> 51<table><thead align="left"><tr id="row1512085253715"><th class="cellrowborder" valign="top" width="42.77%" id="mcps1.2.3.1.1"><p id="p16120175233720"><a name="p16120175233720"></a><a name="p16120175233720"></a>Parameter</p> 52</th> 53<th class="cellrowborder" valign="top" width="57.230000000000004%" id="mcps1.2.3.1.2"><p id="p61205526372"><a name="p61205526372"></a><a name="p61205526372"></a>Description</p> 54</th> 55</tr> 56</thead> 57<tbody><tr id="row11120135213714"><td class="cellrowborder" valign="top" width="42.77%" headers="mcps1.2.3.1.1 "><p id="p1053212673917"><a name="p1053212673917"></a><a name="p1053212673917"></a>__init_array_start__</p> 58</td> 59<td class="cellrowborder" valign="top" width="57.230000000000004%" headers="mcps1.2.3.1.2 "><p id="p2208154219392"><a name="p2208154219392"></a><a name="p2208154219392"></a>Start of the <strong id="b13329113893818"><a name="b13329113893818"></a><a name="b13329113893818"></a>init_array</strong> section</p> 60</td> 61</tr> 62<tr id="row1591908143918"><td class="cellrowborder" valign="top" width="42.77%" headers="mcps1.2.3.1.1 "><p id="p491968193914"><a name="p491968193914"></a><a name="p491968193914"></a>__init_array_end__</p> 63</td> 64<td class="cellrowborder" valign="top" width="57.230000000000004%" headers="mcps1.2.3.1.2 "><p id="p6919189393"><a name="p6919189393"></a><a name="p6919189393"></a>End of the <strong id="b48960753912"><a name="b48960753912"></a><a name="b48960753912"></a>init_array</strong> section</p> 65</td> 66</tr> 67</tbody> 68</table> 69 70> **NOTE:** 71>The **LOS\_CppSystemInit** function must be called before a C++ service. When the C library used by the third-party compiler is not musl libc, some classes or APIs \(such as **std::thread** and **std::mutex**\) that are closely related to system resources have compatibility issues and are not recommended to use. 72 73### Development Example<a name="section994427141111"></a> 74 75``` 76void app_init(void) 77{ 78...... 79/* Initialize C++ in the startup phase. */ 80LOS_CppSystemInit((UINTPTR)&__init_array_start__, (UINTPTR)&__init_array_end__); 81/* C++ service */ 82...... 83} 84``` 85 86
