Android NDK 内存泄露检测

前言

最近写C++代码，老是担心代码存在内存泄露，胆战心惊的，Andorid中Java层代码内存泄露可以借助leakcanary进行检测；找了一番，找到了PC上C++上的内存泄露检测库LeakTracer，于是再找了下，找到了Android上的移植版。

首先建立一个项目，在根目录下建立thirdparty目录，进入该目录，clone相关库代码

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

在项目src/main/cpp下建立CMakeLists.txt，内容如下

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
  #检测c代码时打开此注释，否则不要打开
  ${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-jni
    SHARED
    ${TEST_FILES})

target_link_libraries(
   test-jni
   leaktracer
   log
)

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

native.h

//
// 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

#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;
}

编写test函数，简单进行内测泄露检测

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");
    }
}

运行程序后调用test函数，将/sdcard/leaks.out pull到项目根目录

1	adb pull /sdcard/leaks.out

其内容类似如下内容

1 2	# LeakTracer report diff_utc_mono=1496511718.682943 leak, time=135120.534718, stack=0x36fd6 0x35a90 0x359a4 0x32fea 0xc952d3d0, size=1, data=�

借助thirdparty/LeakTracer/helper/leak-analyze-addr2line工具还原内测泄露堆栈。

进入项目根目录，执行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，会出现一个错误，原因是leak-analyze-addr2line中用到了addr2line工具，而mac上如果没有此工具，就会报错，错误如下：

解决方法很简单，将ndk目录中的arm-linux-androideabi-addr2line拷到./thirdparty/LeakTracer/helpers/下，并重命名为addr2line，然后将./thirdparty/LeakTracer/helpers/加到环境变量中，如下代码

1
2

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

$ANDROID_NDK_HOME表示ndk的根目录。

之后再次调用命令

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

这时候输出如下

native.cpp:15行出现泄露，找到15行对应的代码，即如下代码出现泄露

1	MemoryTest *memoryTest = new MemoryTest;

加入delete代码，再跑一次

1 2	MemoryTest *memoryTest = new MemoryTest; delete memoryTest;

输出如下

发现之前的泄露不见了

最后，值得注意的是，要想使用LeakTracer需要保留so足够多的debug信息，否则可能不能正常检测。

项目Demo地址见NDKMemoryLeakSample