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1# Subscribing to Address Sanitizer Events (ArkTS)
2
3## Available APIs
4
5For details about how to use the APIs, see [@ohos.hiviewdfx.hiAppEvent (Application Event Logging)](../reference/apis-performance-analysis-kit/js-apis-hiviewdfx-hiappevent.md).
6
7| API| **Description**|
8| -------- | -------- |
9| addWatcher(watcher: Watcher): AppEventPackageHolder | Adds a watcher to subscribe to application events.|
10| removeWatcher(watcher: Watcher): void | Removes a watcher to unsubscribe from application events.|
11
12## **How to Develop**
13
14The following describes how to subscribe an address sanitizer event for an array bounds write.
15
16### Step 1: Creating a Project
17
181. Create a native C++ project. The directory structure is as follows:
19
20   ```yml
21   entry:
22     src:
23       main:
24         cpp:
25           - types:
26               libentry:
27                 - index.d.ts
28           - CMakeLists.txt
29           - napi_init.cpp
30         ets:
31           - entryability:
32               - EntryAbility.ets
33           - pages:
34               - Index.ets
35   ```
36
372. In the **entry/src/main/ets/entryability/EntryAbility.ets** file of the project, import the dependent modules.
38
39   ```ts
40   import { hiAppEvent, hilog } from '@kit.PerformanceAnalysisKit';
41   ```
42
43### Step 2: Subscribing to Address Sanitizer Events
44
451. In the **entry/src/main/ets/entryability/EntryAbility.ets** file of the project, add a watcher in **onCreate()** to subscribe to system events. The sample code is as follows:
46
47   ```ts
48   hiAppEvent.addWatcher({
49     // Set the watcher name. The system identifies different watchers based on their names.
50     name: "watcher",
51     // You can subscribe to system events that you are interested in. For example, the address sanitizer event.
52     appEventFilters: [
53
54         domain: hiAppEvent.domain.OS,
55         names: [hiAppEvent.event.ADDRESS_SANITIZER]
56       }
57     ],
58     // Implement a callback for the registered system event so that you can apply custom processing to the event data obtained.
59     onReceive: (domain: string, appEventGroups: Array<hiAppEvent.AppEventGroup>) => {
60       hilog.info(0x0000, 'testTag', `HiAppEvent onReceive: domain=${domain}`);
61       for (const eventGroup of appEventGroups) {
62         // The event name uniquely identifies a system event.
63         hilog.info(0x0000, 'testTag', `HiAppEvent eventName=${eventGroup.name}`);
64         for (const eventInfo of eventGroup.appEventInfos) {
65           // Customize how to process the event data obtained, for example, print the event data in the log.
66           hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.domain=${eventInfo.domain}`);
67           hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.name=${eventInfo.name}`);
68           hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.eventType=${eventInfo.eventType}`);
69           hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.time=${eventInfo.params['time']}`);
70           hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.bundle_version=${eventInfo.params['bundle_version']}`);
71           hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.bundle_name=${eventInfo.params['bundle_name']}`);
72           hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.pid=${eventInfo.params['pid']}`);
73           hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.uid=${eventInfo.params['uid']}`);
74           hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.type=${eventInfo.params['type']}`);
75           hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.external_log=${JSON.stringify(eventInfo.params['external_log'])}`);
76           hilog.info(0x0000, 'testTag', `HiAppEvent eventInfo.log_over_limit=${eventInfo.params['log_over_limit']}`);
77         }
78       }
79     }
80   });
81   ```
82
83### Step 3: Constructing an Address Sanitizer Error
84
851. In the **entry/src/main/cpp/napi_init.cpp** file, implement the array bounds write scenario and provide Node-API for the application layer code to call. The sample code is as follows:
86
87   ```c++
88   #include "napi/native_api.h"
89
90   static napi_value Test(napi_env env, napi_callback_info info)
91   {
92       int a[10];
93       // Construct the array bounds write.
94       a[10] = 1;
95       return {};
96   }
97
98   EXTERN_C_START
99   static napi_value Init(napi_env env, napi_value exports)
100   {
101       napi_property_descriptor desc[] = {
102           { "test", nullptr, Test, nullptr, nullptr, nullptr, napi_default, nullptr }
103       };
104       napi_define_properties(env, exports, sizeof(desc) / sizeof(desc[0]), desc);
105       return exports;
106   }
107   EXTERN_C_END
108
109   static napi_module demoModule = {
110       .nm_version = 1,
111       .nm_flags = 0,
112       .nm_filename = nullptr,
113       .nm_register_func = Init,
114       .nm_modname = "entry",
115       .nm_priv = ((void*)0),
116       .reserved = { 0 }
117   };
118
119   extern "C" __attribute__((constructor)) void RegisterEntryModule(void)
120   {
121       napi_module_register(&demoModule);
122   }
123   ```
124
1252. Edit the **entry/src/main/cpp/types/libentry/index.d.ts** file. The sample code is as follows:
126
127   ```ts
128   export const test: () => void;
129   ```
130
1313. In the **entry > src > main > ets > pages > Index.ets** file, add a button to trigger an address sanitizer event.
132
133   ```ts
134   import testNapi from 'libentry.so';
135
136   @Entry
137   @Component
138   struct Index {
139     build() {
140       Row() {
141         Column() {
142           Button("address-sanitizer").onClick(() => {
143             testNapi.test();
144           })
145         }
146         .width('100%')
147       }
148       .height('100%')
149     }
150   }
151   ```
152
1534. 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.
154
155   ```text
156   HiAppEvent onReceive: domain=OS
157   HiAppEvent eventName=ADDRESS_SANITIZER
158   HiAppEvent eventInfo.domain=OS
159   HiAppEvent eventInfo.name=ADDRESS_SANITIZER
160   HiAppEvent eventInfo.eventType=1
161   HiAppEvent eventInfo.time=1713161197957
162   HiAppEvent eventInfo.bundle_version=1.0.0
163   HiAppEvent eventInfo.bundle_name=com.example.myapplication
164   HiAppEvent eventInfo.pid=12889
165   HiAppEvent eventInfo.uid=20020140
166   HiAppEvent eventInfo.type=stack-buffer-overflow
167   HiAppEvent eventInfo.external_log=["/data/storage/el2/log/hiappevent/ADDRESS_SANITIZER_1713161197960_12889.log"]
168   HiAppEvent eventInfo.log_over_limit=false
169   ```
170