1# Subscribing to Address Sanitizer Events (C/C++)
2
3## **Available APIs**
4
5For details about how to use the APIs (such as parameter usage restrictions and value ranges), see [HiAppEvent](../reference/apis-performance-analysis-kit/_hi_app_event.md#hiappevent).
6
7**Subscription APIs**:
8
9| **API**                                                      | **Description**                                        |
10| ------------------------------------------------------------ | -------------------------------------------- |
11| int OH_HiAppEvent_AddWatcher(HiAppEvent_Watcher \*watcher)   | Adds a watcher to listen for application events.|
12| int OH_HiAppEvent_RemoveWatcher (HiAppEvent_Watcher \*watcher) | Removes a watcher for the specified application events.|
13
14## **How to Develop**
15
16The following describes how to subscribe an address sanitizer event for an array bounds write.
17
181. Create a native C++ project and import the **jsoncpp** file to the project. The directory structure is as follows:
19
20   ```yml
21   entry:
22     src:
23       main:
24         cpp:
25           - json:
26               - json.h
27               - json-forwards.h
28           - types:
29               libentry:
30                 - index.d.ts
31           - CMakeLists.txt
32           - napi_init.cpp
33           - jsoncpp.cpp
34         ets:
35           - entryability:
36               - EntryAbility.ets
37           - pages:
38               - Index.ets
39   ```
40
412. In the **CMakeLists.txt** file, add the source file and dynamic libraries.
42
43   ```cmake
44   # Add the jsoncpp.cpp file, which is used to parse the JSON strings in the subscription events.
45   add_library(entry SHARED napi_init.cpp jsoncpp.cpp)
46   # Add libhiappevent_ndk.z.so and libhilog_ndk.z.so (log output). 
47   target_link_libraries(entry PUBLIC libace_napi.z.so libhilog_ndk.z.so libhiappevent_ndk.z.so)
48   ```
49
503. Import the dependency files to the **napi_init.cpp** file, and define **LOG_TAG**.
51
52   ```c++
53   # include "json/json.h"
54   # include "hilog/log.h"
55   # include "hiappevent/hiappevent.h"
56   
57   # undef LOG_TAG
58   # define LOG_TAG "testTag"
59   ```
60
614. Subscribe to application events. 
62
63   - Watcher of the onReceive type:
64
65     In the **napi_init.cpp** file, define the methods related to the watcher of the onReceive type.
66
67     ```c++
68     // Define a variable to cache the pointer to the created watcher.
69     static HiAppEvent_Watcher *systemEventWatcher; 
70
71     static void OnReceive(const char *domain, const struct HiAppEvent_AppEventGroup *appEventGroups, uint32_t groupLen) {
72         for (int i = 0; i < groupLen; ++i) {
73             for (int j = 0; j < appEventGroups[i].infoLen; ++j) {
74                 OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.domain=%{public}s", appEventGroups[i].appEventInfos[j].domain);
75                 OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.name=%{public}s", appEventGroups[i].appEventInfos[j].name);
76                 OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.eventType=%{public}d", appEventGroups[i].appEventInfos[j].type);
77                 if (strcmp(appEventGroups[i].appEventInfos[j].domain, DOMAIN_OS) == 0 && 
78                     strcmp(appEventGroups[i].appEventInfos[j].name, EVENT_ADDRESS_SANITIZER) == 0) {
79                     Json::Value params;
80                     Json::Reader reader(Json::Features::strictMode());
81                     Json::FastWriter writer;
82                     if (reader.parse(appEventGroups[i].appEventInfos[j].params, params)) {
83                         auto time = params["time"].asInt64();
84                         auto bundleVersion = params["bundle_version"].asString();
85                         auto bundleName = params["bundle_name"].asString();
86                         auto pid = params["pid"].asInt();
87                         auto uid = params["uid"].asInt();
88                         auto type = params["type"].asString();
89                         auto boolFlag = params["log_over_limit"].asBool();
90                         std::string logOverLimit = params["log_over_limit"].asBool() ? "true" : "false";
91                         auto externalLog = writer.write(params["external_log"]);
92                         OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.params.time=%{public}lld", time);
93                         OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.params.bundle_version=%{public}s", bundleVersion.c_str());
94                         OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.params.bundle_name=%{public}s", bundleName.c_str());
95                         OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.params.pid=%{public}d", pid);
96                         OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.params.uid=%{public}d", uid);
97                         OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.params.type=%{public}s", type.c_str());
98                         OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.params.external_log=%{public}s", externalLog.c_str());
99                         OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.params.log_over_limit=%{public}s", logOverLimit.c_str());
100                     }
101                 }
102             }
103         }
104     }
105
106     static napi_value RegisterWatcher(napi_env env, napi_callback_info info) {
107         // Set the watcher name. The system identifies different watchers based on their names.
108         systemEventWatcher = OH_HiAppEvent_CreateWatcher("onReceiverWatcher");
109         // Set the event type to EVENT_ADDRESS_SANITIZER.
110         const char *names[] = {EVENT_ADDRESS_SANITIZER};
111         // Add the system events to watch, for example, system events.
112         OH_HiAppEvent_SetAppEventFilter(systemEventWatcher, DOMAIN_OS, 0, names, 1);
113         // Set the implemented callback. After receiving the event, the watcher immediately triggers the OnReceive callback.
114         OH_HiAppEvent_SetWatcherOnReceive(systemEventWatcher, OnReceive);
115         // Add a watcher to listen for the specified event.
116         OH_HiAppEvent_AddWatcher(systemEventWatcher);
117         return {};
118     }
119     ```
120
121   - Watcher of the onTrigger type:
122
123     In the **napi_init.cpp** file, define the methods related to the watcher of the OnTrigger type.
124
125     ```c++
126     // Define a variable to cache the pointer to the created watcher.
127     static HiAppEvent_Watcher *systemEventWatcher;
128     
129     // Implement the callback function used to return the listened events. The content pointed by the events pointer is valid only in this function.
130     static void OnTake(const char *const *events, uint32_t eventLen) {
131         Json::Reader reader(Json::Features::strictMode());
132         Json::FastWriter writer;
133         for (int i = 0; i < eventLen; ++i) {
134             Json::Value eventInfo;
135             if (reader.parse(events[i], eventInfo)) {
136                 auto domain =  eventInfo["domain_"].asString();
137                 auto name = eventInfo["name_"].asString();
138                 auto type = eventInfo["type_"].asInt();
139                 OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.domain=%{public}s", domain.c_str());
140                 OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.name=%{public}s", name.c_str());
141                 OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.eventType=%{public}d", type);
142                 if (domain ==  DOMAIN_OS && name == EVENT_ADDRESS_SANITIZER) {
143                     auto time = eventInfo["time"].asInt64();
144                     auto bundleVersion = eventInfo["bundle_version"].asString();
145                     auto bundleName = eventInfo["bundle_name"].asString();
146                     auto pid = eventInfo["pid"].asInt();
147                     auto uid = eventInfo["uid"].asInt();
148                     auto asanType = eventInfo["type"].asString();
149                     auto externalLog = writer.write(eventInfo["external_log"]);
150                     std::string logOverLimit = eventInfo["log_over_limit"].asBool() ? "true" : "false";
151                     OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.params.time=%{public}lld", time);
152                     OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.params.bundle_version=%{public}s", bundleVersion.c_str());
153                     OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.params.bundle_name=%{public}s", bundleName.c_str());
154                     OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.params.pid=%{public}d", pid);
155                     OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.params.uid=%{public}d", uid);
156                     OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.params.crash_type=%{public}s", asanType.c_str());
157                     OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.params.external_log=%{public}s", externalLog.c_str());
158                     OH_LOG_INFO(LogType::LOG_APP, "HiAppEvent eventInfo.params.log_over_limit=%{public}s", logOverLimit.c_str());
159                 }
160             }
161         }
162     }
163     
164     // Implement the subscription callback function to apply custom processing to the obtained event logging data.
165     static void OnTrigger(int row, int size) {
166         // After the callback is received, obtain the specified number of received events.
167         OH_HiAppEvent_TakeWatcherData(systemEventWatcher, row, OnTake);
168     }
169     
170     static napi_value RegisterWatcher(napi_env env, napi_callback_info info) {
171         // Set the watcher name. The system identifies different watchers based on their names.
172         systemEventWatcher = OH_HiAppEvent_CreateWatcher("onTriggerWatcher");
173         // Set the event type to EVENT_ADDRESS_SANITIZER.
174         const char *names[] = {EVENT_ADDRESS_SANITIZER};
175         // Add the system events to watch, for example, system events.
176         OH_HiAppEvent_SetAppEventFilter(systemEventWatcher, DOMAIN_OS, 0, names, 1);
177         // Set the implemented callback function. The callback function will be triggered when the conditions set by OH_HiAppEvent_SetTriggerCondition are met.
178         OH_HiAppEvent_SetWatcherOnTrigger(systemEventWatcher, OnTrigger);
179         // Set the conditions for triggering the subscription callback. For example, trigger this onTrigger callback when the number of new event logs is 1.
180         OH_HiAppEvent_SetTriggerCondition(systemEventWatcher, 1, 0, 0);
181         // Add a watcher to listen for the specified event.
182         OH_HiAppEvent_AddWatcher(systemEventWatcher);
183         return {};
184     }
185     ```
186
1875. Construct an address out-of-bounds error.
188   
189   In the **napi_init.cpp** file, define a **Test** method to perform out-of-bounds access on an integer array.
190
191   ```c++
192   static napi_value Test(napi_env env, napi_callback_info info)
193   {
194       int a[10];
195       a[10] = 1;
196       return {};
197   }
198   ```
199
2006. Register **RegisterWatcher** and **Test** as ArkTS APIs.
201
202   In the **napi_init.cpp** file, register **RegisterWatcher** and **Test** as ArkTS APIs.
203
204   ```c++
205   static napi_value Init(napi_env env, napi_value exports)
206   {
207       napi_property_descriptor desc[] = {
208           { "registerWatcher", nullptr, RegisterWatcher, nullptr, nullptr, nullptr, napi_default, nullptr },
209           { "test", nullptr, Test, nullptr, nullptr, nullptr, napi_default, nullptr}
210       };
211       napi_define_properties(env, exports, sizeof(desc) / sizeof(desc[0]), desc);
212       return exports;
213   }
214   ```
215
216   In the **index.d.ts** file, define ArkTS APIs.
217
218   ```typescript
219   export const registerWatcher: () => void;
220   export const test: () => void;
221   ```
222
2237. In the **EntryAbility.ets** file, add the following interface invocation to **onCreate()**.
224
225   ```typescript
226   // Import the dependent module.
227   import testNapi from 'libentry.so'
228
229   // Add the interface invocation to onCreate().
230   // Register the system event watcher at startup.
231   testNapi.registerWatcher();
232   ```
233
2348. In the **entry/src/main/ets/pages/Index.ets** file, add a button to trigger the address sanitizer event.
235
236   ```ts
237   import testNapi from 'libentry.so'
238
239   @Entry
240   @Component
241   struct Index {
242     build() {
243       Row() {
244         Column() {
245           Button("address-sanitizer").onClick(() => {
246             testNapi.test();
247           })
248         }
249         .width('100%')
250       }
251       .height('100%')
252     }
253   }
254   ```
255
2569. In DevEco Studio, choose **entry**, click **Edit Configurations**, click **Diagnostics**, select **Address Sanitizer**, and click **OK**. Click the **Run** button to run the project. Then, click the **address-sanitizer** button to trigger an address sanitizer event. The application crashes. After restarting the application, you can view the following event information in the **Log** window.
257
258   ```text
259   HiAppEvent eventInfo.domain=OS
260   HiAppEvent eventInfo.name=ADDRESS_SANITIZER
261   HiAppEvent eventInfo.eventType=1
262   HiAppEvent eventInfo.params.time=1713148093326
263   HiAppEvent eventInfo.params.bundle_version=1.0.0
264   HiAppEvent eventInfo.params.bundle_name=com.example.myapplication
265   HiAppEvent eventInfo.params.pid=3378
266   HiAppEvent eventInfo.params.uid=20020140
267   HiAppEvent eventInfo.params.type="stack-buffer-overflow"
268   HiAppEvent eventInfo.params.external_log=["/data/storage/el2/log/hiappevent/ADDRESS_SANITIZER_1713148093326_3378.log"]
269   HiAppEvent eventInfo.params.log_over_limit=false
270   ```
271
27210. Remove the application event watcher.
273
274    ```c++
275    static napi_value RemoveWatcher(napi_env env, napi_callback_info info) {
276        // Remove the watcher.
277        OH_HiAppEvent_RemoveWatcher(systemEventWatcher);
278        return {};
279    }
280    ```
281
28211. Destroy the application event watcher.
283
284    ```c++
285    static napi_value DestroyWatcher(napi_env env, napi_callback_info info) {
286        // Destroy the created watcher and set systemEventWatcher to nullptr.
287        OH_HiAppEvent_DestroyWatcher(systemEventWatcher);
288        systemEventWatcher = nullptr;
289        return {};
290    }
291    ```
292
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