【发布时间】：2012-06-22 07:23:26
【问题描述】：
第一次使用 JNI 访问 c 库时，我想到了使用 valgrind 来检查任何内存泄漏。 Valgrind 在 jvm 中报告了很多泄漏。:(
使用 Push/Poplocal 框架来管理本地引用，当然还需要从 Get(UTFChars/Arrays) 释放引用。除此之外，它还报告 AttachCurrentThread 方法可能丢失，而实际上我通过回调函数中的 DetachCurrentThread 成功分离了它。
现在我只需要建议/解释报告的泄漏根本不是真的，不会影响我的应用程序，尤其是它在服务器端的应用程序。对我来说，我怀疑在我的应用程序退出并且 valgrind 已经完成检查部分之后，库的卸载和销毁尚未完成。希望也有遇到过这种情况的人来听听。
//示例代码
void event_callback(void .., int ..)
{
printf("--Enter event_callback Function--\n");
int detach = 0;
//store our jnienv for this thread
JNIEnv *g_env = NULL;
// if our jni env is not attached for this thread, then we will attach it
int getEnvStat = (*g_jvm)->GetEnv(g_jvm, (void **)&g_env, JNI_VERSION_1_6);
if (getEnvStat == JNI_EDETACHED)
{
//if not attached, then lets attached g_env
printf("JNIEnv not attached. Attaching..\n");
if ((*g_jvm)->AttachCurrentThread(g_jvm, (void **) &g_env, NULL) != 0)
{
printf("Failed to attach\n");
return;
}
else
{
detach = 1;
}
}
else if (getEnvStat == JNI_OK)
{
printf("GetEnv: jenv is just OK, already attached.\n");
}
else if (getEnvStat == JNI_EVERSION)
{
printf("GetEnv: version not supported\n");
return;
}
if((*g_env)->PushLocalFrame(g_env, 10)<0)
{
printf("Out of memory\n");
}
//...some useful code here
(*g_env)->PopLocalFrame(g_env, NULL);
if(detach == 1)
{
int result = (*g_jvm)->DetachCurrentThread(g_jvm);
printf("DetachCurrentThread result: %d\n", result);
}
printf("--Exit event_callback Function--\n");
}
报告：
==20914== 1,035 的丢失记录 903 中可能丢失 1 个块中的 432 个字节
==20914== at 0x4028876: malloc (vg_replace_malloc.c:236)
==20914== by 0x4950461: os::malloc(unsigned int) (在/usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client/libjvm.so)
==20914== by 0x464470C: CHeapObj::operator new(unsigned int) (在 /usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client/libjvm.so)
==20914== by 0x496BB13: ParkEvent::Allocate(Thread*) (在 /usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client/libjvm.so)
==20914== by 0x4A13CCD: Thread::Thread()（在 /usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client/libjvm.so 中）
==20914== by 0x4A15091：JavaThread::JavaThread(bool)（在 /usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client/libjvm.so 中）
==20914== by 0x4853723: attach_current_thread.isra.103.part.104（在/usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client/libjvm.so）
==20914== by 0x7B17791：event_callback（在 /home/Wrapper/TJNIBridge/libJNIBridge.so 中）
==20914== by 0x7B44431: xmpp_event_main (my_xmpp.c:562)
==20914== by 0x412146D: 克隆 (clone.S:130)
我还在 jvm lib 下方粘贴了一些报告的泄漏。
==20914== 1 个块中的 4,612（1,284 个直接，3,328 个间接）字节在 1,035 个中的第 1,009 个丢失记录中肯定丢失了
==20914== at 0x4028876: malloc (vg_replace_malloc.c:236)
==20914== by 0x4950461: os::malloc(unsigned int) (在/usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client/libjvm.so)
==20914== by 0x464470C: CHeapObj::operator new(unsigned int) (在 /usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client/libjvm.so)
==20914== by 0x4A14BE9：WatcherThread::start()（在 /usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client/libjvm.so 中）
==20914== by 0x4A192DF: Threads::create_vm(JavaVMInitArgs*, bool*) (在 /usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client/libjvm.so )
==20914== by 0x4865BD8：JNI_CreateJavaVM（在 /usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client/libjvm.so 中）
==20914== by 0x41ECD30: start_thread (pthread_create.c:304)
==20914== by 0x412146D: 克隆 (clone.S:130)
==20914== 1 个块中的 8 个字节在 1,035 的丢失记录 41 中肯定丢失了
==20914== at 0x4028876: malloc (vg_replace_malloc.c:236)
==20914== by 0x4950461: os::malloc(unsigned int) (在/usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client/libjvm.so)
==20914== by 0x464470C: CHeapObj::operator new(unsigned int) (在 /usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client/libjvm.so)
==20914== by 0x470E29D: CSpaceCounters::CSpaceCounters(char const*, int, unsigned int, ContiguousSpace*, GenerationCounters*) (在 /usr/lib/jvm/java-7-openjdk-i386/jre/ lib/i386/client/libjvm.so)
==20914== by 0x47A3BF9: DefNewGeneration::DefNewGeneration(ReservedSpace, unsigned int, int, char const*) (在 /usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/客户端/libjvm.so)
==20914== by 0x47FC623: GenerationSpec::init(ReservedSpace, int, GenRemSet*) (在 /usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client/libjvm.所以）
==20914== by 0x47EF9D4: GenCollectedHeap::initialize()（在 /usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client/libjvm.so 中）
==20914== 由 0x4B95FF3: ??? （在/usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/client/libjvm.so）
Ubuntu 11.10 OpenJDK 7
【问题讨论】：
标签： jvm memory-leaks valgrind