我正在为所有项目使用AddressSanitizer来检测内存泄漏，堆损坏等。但是，在运行时通过dlopen加载动态库时，AddressSanitizer的输出还有很多不足之处。我写了一个简单的测试程序来说明问题。代码本身并不有趣，只是两个库，一个在编译时通过-l链接，另一个在运行时用dlopen加载。为了完整起见，这里是我用于测试的代码：
// ----------------------------------------------------------------------------
// dllHelper.hpp
#pragma once
#include <string>
#include <sstream>
#include <iostream>
#include <errno.h>
#include <dlfcn.h>
// Generic helper definitions for shared library support
#if defined WIN32
#define MY_DLL_EXPORT __declspec(dllexport)
#define MY_DLL_IMPORT __declspec(dllimport)
#define MY_DLL_LOCAL
#define MY_DLL_INTERNAL
#else
#if __GNUC__ >= 4
#define MY_DLL_EXPORT __attribute__ ((visibility ("default")))
#define MY_DLL_IMPORT __attribute__ ((visibility ("default")))
#define MY_DLL_LOCAL __attribute__ ((visibility ("hidden")))
#define MY_DLL_INTERNAL __attribute__ ((visibility ("internal")))
#else
#define MY_DLL_IMPORT
#define MY_DLL_EXPORT
#define MY_DLL_LOCAL
#define MY_DLL_INTERNAL
#endif
#endif
void* loadLibrary(const std::string& filename) {
void* module = dlopen(filename.c_str(), RTLD_NOW | RTLD_GLOBAL);
if(module == nullptr) {
char* error = dlerror();
std::stringstream stream;
stream << "Error trying to load the library. Filename: " << filename << " Error: " << error;
std::cout << stream.str() << std::endl;
}
return module;
}
void unloadLibrary(void* module) {
dlerror(); //clear all errors
int result = dlclose(module);
if(result != 0) {
char* error = dlerror();
std::stringstream stream;
stream << "Error trying to free the library. Error code: " << error;
std::cout << stream.str() << std::endl;
}
}
void* loadFunction(void* module, const std::string& functionName) {
if(!module) {
std::cerr << "Invalid module" << std::endl;
return nullptr;
}
dlerror(); //clear all errors
#ifdef __GNUC__
__extension__
#endif
void* result = dlsym(module, functionName.c_str());
char* error;
if((error = dlerror()) != nullptr) {
std::stringstream stream;
stream << "Error trying to get address of function \"" << functionName << "\" from the library. Error code: " << error;
std::cout << stream.str() << std::endl;
}
return result;
}
// ----------------------------------------------------------------------------
// testLib.hpp
#pragma once
#include "dllHelper.hpp"
#ifdef TESTLIB
#define TESTLIB_EXPORT MY_DLL_EXPORT
#else
#define TESTLIB_EXPORT MY_DLL_IMPORT
#endif
namespace TestLib {
// will be linked at compile time
class TESTLIB_EXPORT LeakerTestLib {
public:
void leak();
};
}
// ----------------------------------------------------------------------------
// testLib.cpp
#include "testLib.hpp"
namespace TestLib {
void LeakerTestLib::leak() {
volatile char* myLeak = new char[10];
(void)myLeak;
}
}
// ----------------------------------------------------------------------------
// testLibRuntime.hpp
#pragma once
#include "dllHelper.hpp"
#ifdef TESTLIBRUNTIME
#define TESTLIBRUNTIME_EXPORT MY_DLL_EXPORT
#else
#define TESTLIBRUNTIME_EXPORT MY_DLL_IMPORT
#endif
namespace TestLibRuntime {
// will be loaded via dlopen at runtime
class TESTLIBRUNTIME_EXPORT LeakerTestLib {
public:
void leak();
};
}
extern "C" {
TestLibRuntime::LeakerTestLib* TESTLIBRUNTIME_EXPORT createInstance();
void TESTLIBRUNTIME_EXPORT freeInstance(TestLibRuntime::LeakerTestLib* instance);
void TESTLIBRUNTIME_EXPORT performLeak(TestLibRuntime::LeakerTestLib* instance);
}
// ----------------------------------------------------------------------------
// testLibRuntime.cpp
#include "testLibRuntime.hpp"
namespace TestLibRuntime {
void LeakerTestLib::leak() {
volatile char* myLeak = new char[10];
(void)myLeak;
}
extern "C" {
LeakerTestLib* createInstance() {
return new LeakerTestLib();
}
void freeInstance(LeakerTestLib* instance) {
delete instance;
}
void performLeak(LeakerTestLib* instance) {
if(instance) {
instance->leak();
}
}
}
}
// ----------------------------------------------------------------------------
// main.cpp
#include "testLib.hpp"
#include "testLibRuntime.hpp"
#define LEAK_TESTLIB
#define LEAK_TESTLIBRUNTIME
int main(int argc, char** argv) {
#ifdef LEAK_TESTLIBRUNTIME
void* testLibRuntimeModule = loadLibrary("libtestLibRuntime.so");
if(!testLibRuntimeModule) {
return -1;
}
TestLibRuntime::LeakerTestLib* testLibRuntime = nullptr;
auto createInstance = (TestLibRuntime::LeakerTestLib * (*)())loadFunction(testLibRuntimeModule, "createInstance");
if(!createInstance) {
return -1;
}
auto freeInstance = (void(*)(TestLibRuntime::LeakerTestLib*))loadFunction(testLibRuntimeModule, "freeInstance");
if(!freeInstance) {
return -1;
}
auto performLeak = (void(*)(TestLibRuntime::LeakerTestLib*))loadFunction(testLibRuntimeModule, "performLeak");
if(!performLeak) {
return -1;
}
testLibRuntime = createInstance();
performLeak(testLibRuntime);
freeInstance(testLibRuntime);
#endif
#ifdef LEAK_TESTLIB
TestLib::LeakerTestLib testLib;
testLib.leak();
#endif
#ifdef LEAK_TESTLIBRUNTIME
unloadLibrary(testLibRuntimeModule);
#endif
return 0;
}
我使用以下命令编译了上面的代码：
clang++ -std=c++11 -O0 -g -ggdb -Wl,-undefined -Wl,dynamic_lookup -fsanitize=address -fsanitize-recover=address -fno-omit-frame-pointer -fsanitize-address-use-after-scope -DTESTLIB -shared -fPIC -o libtestLib.so testLib.cpp -ldl -shared-libasan
clang++ -std=c++11 -O0 -g -ggdb -Wl,-undefined -Wl,dynamic_lookup -fsanitize=address -fsanitize-recover=address -fno-omit-frame-pointer -fsanitize-address-use-after-scope -DTESTLIBRUNTIME -shared -fPIC -o libtestLibRuntime.so testLibRuntime.cpp -ldl -shared-libasan
clang++ -std=c++11 -O0 -g -ggdb -Wl,-undefined -Wl,dynamic_lookup -fsanitize=address -fsanitize-recover=address -fno-omit-frame-pointer -fsanitize-address-use-after-scope -o leak main.cpp -ldl -L./ -ltestLib -shared-libasan
当我运行程序时，我得到以下输出（我必须预先导出LD_LIBRARY_PATH才能找到libasan）：
$ export LD_LIBRARY_PATH=/usr/lib/clang/4.0.0/lib/linux/:./
$ ./leak
=================================================================
==4210==ERROR: LeakSanitizer: detected memory leaks
Direct leak of 10 byte(s) in 1 object(s) allocated from:
#0 0x7fb665a210f0 in operator new[](unsigned long) (/usr/lib/clang/4.0.0/lib/linux/libclang_rt.asan-x86_64.so+0x10e0f0)
#1 0x7fb66550d58a in TestLib::LeakerTestLib::leak() /home/jae/projects/clang_memcheck/testLib.cpp:6:29
#2 0x402978 in main /home/jae/projects/clang_memcheck/main.cpp:37:13
#3 0x7fb6648d4439 in __libc_start_main (/usr/lib/libc.so.6+0x20439)
Direct leak of 10 byte(s) in 1 object(s) allocated from:
#0 0x7fb665a210f0 in operator new[](unsigned long) (/usr/lib/clang/4.0.0/lib/linux/libclang_rt.asan-x86_64.so+0x10e0f0)
#1 0x7fb6617fd6da (<unknown module>)
#2 0x7fb6617fd75f (<unknown module>)
#3 0x402954 in main /home/jae/projects/clang_memcheck/main.cpp:31:5
#4 0x7fb6648d4439 in __libc_start_main (/usr/lib/libc.so.6+0x20439)
SUMMARY: AddressSanitizer: 20 byte(s) leaked in 2 allocation(s).
在检测到泄漏的同时，AddressSanitizer似乎无法解析通过dlopen（打印（＆lt; unknown module＆gt;））加载的库的模块名称，函数名称和行号，而在编译时链接的库时间完美无瑕。我的问题是：
是否可以使用某些编译器开关修复此问题，或者在使用dlopen加载的库时无法使用AddressSanitizer获取更多信息？显然可以找到llvm-symbolizer，或者没有其他库的行号。使用
运行程序ASAN_OPTIONS=symbolize=1 ASAN_SYMBOLIZER_PATH=/usr/bin/llvm-symbolizer ./leak
不会导致不同的输出。我用g ++编译了程序，但输出保持不变。我也通过asan_symbolize.py管道输出，但没有任何改变。我不知道接下来要去哪儿。我的想法中有一个根本性的错误吗？在动态加载库时，我不是专家。
答案 0 :(得分：1)
在动态加载库中跟踪此类问题时，我一直在偷工减料，但我只是省略了库卸载代码以进行测试，因此当程序终止时，符号仍可用于清理程序（和valgrind）。虽然这样做可能会导致一些错误的泄漏检测，因为dlopen分配的人员不会被释放。
似乎没有适当的解决方案来解决这个问题，因为在卸载库之后，没有什么能阻止在同一地址加载另一个库。
答案 1 :(得分：1)
这是ASan中的已知错误（请参阅Issue 89）。它已经存在了一段时间，但似乎没有人有动力去解决它。