前言

最近寫C++代碼，老是擔心代碼存在內存泄露，膽戰心驚的，Andorid中Java層代碼內存泄露可以借助leakcanary進行檢測；找了一番，找到了PC上C++上的內存泄露檢測庫LeakTracer，于是再找了下，找到了Android上的移植版。

首先建立一個項目，在根目錄下建立thirdparty目錄，進入該目錄，clone相關庫代碼

1	git clone git@github.com:lizhangqu/LeakTracer.git

在項目src/main/cpp下建立CMakeLists.txt，內容如下

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project(Test)cmake_minimum_required (VERSION 3.6)include_directories( ${PROJECT_SOURCE_DIR}/include/ ${PROJECT_SOURCE_DIR}/../../../../thirdparty/LeakTracer/libleaktracer/include/)set(LEAKTRACER_SOURCES ${PROJECT_SOURCE_DIR}/../../../../thirdparty/LeakTracer/libleaktracer/src/AllocationHandlers.cpp#${PROJECT_SOURCE_DIR}/../../../../thirdparty/LeakTracer/libleaktracer/src/LeakTracerC.c#檢測c代碼時打開此注釋，否則不要打開 ${PROJECT_SOURCE_DIR}/../../../../thirdparty/LeakTracer/libleaktracer/src/MemoryTrace.cpp)add_library(leaktracer STATIC ${LEAKTRACER_SOURCES})set(TEST_FILES ${CMAKE_SOURCE_DIR}/native.cpp)add_library(test-jniSHARED ${TEST_FILES})target_link_libraries(test-jnileaktracerlog)

建立src/main/cpp/include/native.h和src/main/cpp/native.cpp文件

native.h

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//// Created by 李樟取 on 2017/6/4.//#ifndef TEST_H#define TEST_H#include "jni.h"#ifndef NELEM# define NELEM(x) ((int) (sizeof(x) / sizeof((x)[0])))#endif#ifndef CLASSNAME#define CLASSNAME "io/github/lizhangqu/test/Test"#endif#ifdef ANDROID#include <android/log.h>#define TAG "Test"#define ALOGE(fmt, ...) __android_log_print(ANDROID_LOG_ERROR, TAG, fmt, ##__VA_ARGS__)#define ALOGI(fmt, ...) __android_log_print(ANDROID_LOG_INFO, TAG, fmt, ##__VA_ARGS__)#define ALOGD(fmt, ...) __android_log_print(ANDROID_LOG_DEBUG, TAG, fmt, ##__VA_ARGS__)#define ALOGW(fmt, ...) __android_log_print(ANDROID_LOG_WARN, TAG, fmt, ##__VA_ARGS__)#else#define ALOGE printf#define ALOGI printf#define ALOGD printf#define ALOGW printf#endif#endif //TEST_H

native.cpp

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#include "native.h"#include "MemoryTrace.hpp"#include <fstream>void test(JNIEnv *env, jobject thiz) { }static const JNINativeMethod sMethods[] = {{ const_cast<char *>("test"), const_cast<char *>("()V"), reinterpret_cast<void *>(test)},};int registerNativeMethods(JNIEnv *env, const char *className, const JNINativeMethod *methods, const int numMethods) {jclass clazz = env->FindClass(className); if (!clazz) {ALOGE("Native registration unable to find class '%s'\n", className); return JNI_FALSE;} if (env->RegisterNatives(clazz, methods, numMethods) != 0) {ALOGE("RegisterNatives failed for '%s'\n", className);env->DeleteLocalRef(clazz); return JNI_FALSE;}env->DeleteLocalRef(clazz); return JNI_TRUE;}jint JNI_OnLoad(JavaVM *vm, void *reserved) {JNIEnv *env; if (vm->GetEnv(reinterpret_cast<void **>(&env), JNI_VERSION_1_6) != JNI_OK) { return -1;}registerNativeMethods(env, CLASSNAME, sMethods, NELEM(sMethods)); return JNI_VERSION_1_6;}

編寫test函數，簡單進行內測泄露檢測

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class MemoryTest {};void test(JNIEnv *env, jobject thiz) {leaktracer::MemoryTrace::GetInstance().startMonitoringAllThreads();MemoryTest *memoryTest = new MemoryTest;leaktracer::MemoryTrace::GetInstance().stopAllMonitoring(); std::ofstream out;out.open("/sdcard/leaks.out", std::ios_base::out); if (out.is_open()) {leaktracer::MemoryTrace::GetInstance().writeLeaks(out);} else {ALOGE("Failed to write to \"leaks.out\"\n");}}

運行程序后調用test函數，將/sdcard/leaks.out pull到項目根目錄

1	adb pull /sdcard/leaks.out

其內容類似如下內容

12	# LeakTracer report diff_utc_mono=1496511718.682943leak, time=135120.534718, stack=0x36fd6 0x35a90 0x359a4 0x32fea 0xc952d3d0, size=1, data=�

借助thirdparty/LeakTracer/helper/leak-analyze-addr2line工具還原內測泄露堆棧。

進入項目根目錄，執行leak-analyze-addr2line

1	./thirdparty/LeakTracer/helpers/leak-analyze-addr2line ./library/build/intermediates/cmake/debug/obj/armeabi/libtest-jni.so ./leaks.out

在mac上，會出現一個錯誤，原因是leak-analyze-addr2line中用到了addr2line工具，而mac上如果沒有此工具，就會報錯，錯誤如下：

解決方法很簡單，將ndk目錄中的arm-linux-androideabi-addr2line拷到./thirdparty/LeakTracer/helpers/下，并重命名為addr2line，然后將./thirdparty/LeakTracer/helpers/加到環境變量中，如下代碼

12	cp $ANDROID_NDK_HOME/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64/bin/arm-linux-androideabi-addr2line ./thirdparty/LeakTracer/helpers/addr2lineexport PATH=$PATH:`pwd`/thirdparty/LeakTracer/helpers

$ANDROID_NDK_HOME表示ndk的根目錄。

之后再次調用命令

1	./thirdparty/LeakTracer/helpers/leak-analyze-addr2line ./library/build/intermediates/cmake/debug/obj/armeabi/libtest-jni.so ./leaks.out

這時候輸出如下

native.cpp:15行出現泄露，找到15行對應的代碼，即如下代碼出現泄露

1	MemoryTest *memoryTest = new MemoryTest;

加入delete代碼，再跑一次

12	MemoryTest *memoryTest = new MemoryTest;delete memoryTest;

輸出如下

發現之前的泄露不見了

最后，值得注意的是，要想使用LeakTracer需要保留so足夠多的debug信息，否則可能不能正常檢測。

項目Demo地址見NDKMemoryLeakSample

http://fucknmb.com/2017/06/05/Android-NDK-%E5%86%85%E5%AD%98%E6%B3%84%E9%9C%B2%E6%A3%80%E6%B5%8B/

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