Memory Microsoft 的 WMI 库中的泄漏。 有没有办法减轻它？

Question

当我们使用IWbemQualifierSet::Put 156KB 的键值对写入 WMI 时，此方法会创建 2GB 的悬空分配。 我从来没有在 Microsoft 库中遇到过这样的错误，所以我不确定该怎么做。

有什么方法可以通过操纵调用堆栈来缓解它吗？ 或者通过在某种隔离容器中为 class 预先分配 memory 以确保它在 class object 被销毁后完全释放？

您可以跳到代码中的“第 3 步”查看泄漏，无论数据类型或格式如何，它都会发生，包括仅使用 C 类型和手动管理 memory。

更新：即使我们在循环中创建和销毁 class object，泄漏仍然发生。

更新：无论输入数据大小如何，泄漏的大小都是相同的。 即使我们写入长度为 4000 字节或 1 字节的字符串，memory 泄漏的数量也是相同的。

主.cpp：

// MemorLeakMinimalExample.cpp : This file contains the 'main' function. Program execution begins and ends there.
#include <string>
#include <Windows.h>
#include "wmi_connection.h"

// Memory leak in this method
// Consumes 2GB of RAM to write 32MB of data

int main()
{

    // ------------------------------------------------------
    // Step 1. Connect to WMI -------------------------------

    wmi_connection wmi;
    wmi.connect_to_wmi();


    // ------------------------------------------------------
    // Step 2. Create a new WMI class -----------------------

    IWbemClassObject* pNewClass = NULL;
    VARIANT vVariant;
    VariantInit(&vVariant);

    // Our new class
    HRESULT hres = wmi.pSvc->GetObject(
        0,
        0,
        NULL,
        &pNewClass,
        NULL
    );

    // Set class name
    vVariant.vt = VT_BSTR;
    vVariant.bstrVal = SysAllocString(L"TestClass");
    hres = pNewClass->Put(
        _bstr_t("__CLASS"),
        0,
        &vVariant,
        0
    );

    // Create the "Test" key property for the new class
    BSTR KeyProp = SysAllocString(L"TestProperty");

    hres = pNewClass->Put(
        KeyProp,
        0,
        NULL,
        CIM_STRING);

    //Attach the Key standard qualifier to the test property
    IWbemQualifierSet* pQualSet = NULL;
    vVariant.vt = VT_BOOL;
    vVariant.boolVal = TRUE;
    hres = pNewClass->GetPropertyQualifierSet(KeyProp, &pQualSet);
    hres = pQualSet->Put(L"Key", &vVariant, 0);
    

    // --------------------------------------------------------------------
    // Step 3. Write 20,000 key:value pairs -------------------------------
    
    // Key
    wchar_t key[32] = { 0 };
    wchar_t* pKey = key;
    
    // Value
    VARIANT value;
    VariantInit(&value);
    value.vt = VT_BSTR;

    // Value is always 1234
    value.bstrVal = SysAllocString(L"1234");
    

    printf("Breakpoint\n"); // Inspect memory usage here

    
    for (unsigned long long i = 0; i <= 20000; i++)
    {
        // Key name is formatted "key0", "key1", "key2", ...
        swprintf_s(pKey, 32, L"key%llu", i);

        // Write a key:value pair
        pQualSet->Put(pKey, &value, 0); // <-- memory leak
        
    }
    
    printf("Breakpoint\n"); // Inspect memory usage here

    // --------------------------------------------------------------------
    // // Step 4. Save class for viewing in sys utility Wbemtest.exe ------

    // Uncomment if you want the class written to the wmi database
    // (its exactly the size it should be for our key:value data in)

    /*
    hres = wmi.pSvc->PutClass(pNewClass, WBEM_FLAG_CREATE_OR_UPDATE, NULL, NULL);
    if (FAILED(hres))
    {
        printf("Failed to save class changes. Error code = 0x%X \n", hres);
    }
    */

    return 0;
}

wmi_connection.h:

#pragma once
#include <Windows.h>
#include <comdef.h>
#include <wbemcli.h>

class wmi_connection
{
public:
    // uninteresting parts
    int connect_to_wmi()
    {
        // Initialize 
        hres = CoInitializeEx(0, COINIT_MULTITHREADED);
        if (FAILED(hres))
        {
            printf("Failed to initialize COM library. Error code = 0x%llx", (unsigned long long)hres);
            return FALSE;                  // Program has failed.
        }
        // Set general COM security levels 
        hres = CoInitializeSecurity(
            NULL,
            -1,                          // COM authentication
            NULL,                        // Authentication services
            NULL,                        // Reserved
            RPC_C_AUTHN_LEVEL_DEFAULT,   // Default authentication 
            RPC_C_IMP_LEVEL_IMPERSONATE, // Default Impersonation  
            NULL,                        // Authentication info
            EOAC_NONE,                   // Additional capabilities 
            NULL                         // Reserved
        );

        // Get the class factory for the WbemLocator object
        IClassFactory* pClassFactory = NULL;

        hres = CoGetClassObject(CSLSID_WbemLocator, CLSCTX_INPROC_SERVER, NULL, SIID_IClassFactory, (void**)&pClassFactory);

        // Create an instance of the WbemLocator object
        IUnknown* pUnk = NULL;

        hres = pClassFactory->CreateInstance(NULL, SIID_IUnknown, (void**)&pUnk);

        hres = pUnk->QueryInterface(SIID_IWbemLocator, (void**)&pLoc);

        pUnk->Release();
        pClassFactory->Release();

        // Set security levels on the proxy 
        hres = CoSetProxyBlanket(
            pSvc,                        // Indicates the proxy to set
            RPC_C_AUTHN_WINNT,           // RPC_C_AUTHN_xxx
            RPC_C_AUTHZ_NONE,            // RPC_C_AUTHZ_xxx
            NULL,                        // Server principal name 
            RPC_C_AUTHN_LEVEL_CALL,      // RPC_C_AUTHN_LEVEL_xxx 
            RPC_C_IMP_LEVEL_IMPERSONATE, // RPC_C_IMP_LEVEL_xxx
            NULL,                        // client identity
            EOAC_NONE                    // proxy capabilities 
        );

        // Connect to WMI through the IWbemLocator::ConnectServer method
        hres = pLoc->ConnectServer(
            _bstr_t(L"root\\cimv2"), // Object path of WMI namespace
            NULL,                    // User name
            NULL,                    // User password
            0,                       // Locale
            NULL,                    // Security flags
            0,                       // Authority
            0,                       // Context object 
            &pSvc                    // pointer to IWbemServices proxy
        );

        if (FAILED(hres))
        {
            printf("Could not connect. Error code = 0x%lx\n", hres);
            return 1;
        }

        printf("Connected to root\cimv2 WMI namespace\n");
        return 0;
    }

    IWbemServices* pSvc;

private:
    HRESULT hres = NULL;
    IWbemLocator* pLoc = NULL;
    GUID CSLSID_WbemLocator = { 0x4590f811, 0x1d3a, 0x11d0, 0x89, 0x1f, 0x00, 0xaa, 0x00, 0x4b, 0x2e, 0x24 };
    GUID SIID_IClassFactory = { 0x00000001, 0x0000, 0x0000, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x46 };
    GUID SIID_IUnknown = { 0x00000000, 0x0000, 0x0000, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x46 };
    GUID SIID_IWbemLocator = { 0xdc12a687, 0x737f, 0x11cf, 0x88, 0x4d, 0x00, 0xaa, 0x00, 0x4b, 0x2e, 0x24 };
};

Answer 1

我把i变成了40000000，发现memory这个footprint确实从任务管理器一直在增加。 并不断地展示这一点。

我添加了Sleep(50); 在“for”循环中，“抛出异常……” 消失了。 但 memory 的足迹仍在增加。 进程 memory 在 6 分钟内增加到 565MB。

“for”循环与Put(pKey, &value, 0);

所以，使用多线程是必要的。

我修改了代码，它运行良好。 对循环没有影响，进程memory正常。

代码如下，还是有很多瑕疵，欢迎大家指正。

#include <string>
#include <Windows.h>
#include "wmi_connection.h"
wchar_t key[32] = { 0 };
wchar_t* pKey = key;
BSTR KeyProp = SysAllocString(L"TestProperty");
IWbemQualifierSet* pQualSet = NULL;
VARIANT value;
DWORD WINAPI ThreadProc1(LPVOID lpParameter)
{
    wmi_connection wmi;
    wmi.connect_to_wmi();
    IWbemClassObject* pNewClass = NULL;
    VARIANT vVariant;
    VariantInit(&vVariant);
    HRESULT hres = wmi.pSvc->GetObject(
        0,
        0,
        NULL,
        &pNewClass,
        NULL
    );
    vVariant.vt = VT_BSTR;
    vVariant.bstrVal = SysAllocString(L"TestClass");
    hres = pNewClass->Put(
        _bstr_t("__CLASS"),
        0,
        &vVariant,
        0
    );
    hres = pNewClass->Put(
        KeyProp,
        0,
        NULL,
        CIM_STRING);
    vVariant.vt = VT_BOOL;
    vVariant.boolVal = TRUE;
    hres = pNewClass->GetPropertyQualifierSet(KeyProp, &pQualSet);
    hres = pQualSet->Put(L"Key", &vVariant, 0);

    VARIANT value;
    VariantInit(&value);
    value.vt = VT_BSTR;

    value.bstrVal = SysAllocString(L"1234");
    printf("Breakpoint\n");
    pQualSet->Put(pKey, &value, 0);
   
    return 2;
}
DWORD WINAPI ThreadProc2(LPVOID lpParameter)
{
    for (unsigned long long i = 0; i <= 400000000; i++)

    {
           
        swprintf_s(pKey, 32, L"key%llu", i);
    }
    printf("Breakpoint\n");
    return 0;
}
int main()
{
    wmi_connection wmi;
    wmi.connect_to_wmi();

    IWbemClassObject* pNewClass = NULL;
    VARIANT vVariant;
    VariantInit(&vVariant);

    // Our new class
    HRESULT hres = wmi.pSvc->GetObject(
        0,
        0,
        NULL,
        &pNewClass,
        NULL
    );

    vVariant.vt = VT_BSTR;
    vVariant.bstrVal = SysAllocString(L"TestClass");
    hres = pNewClass->Put(
        _bstr_t("__CLASS"),
        0,
        &vVariant,
        0
    );
    BSTR KeyProp = SysAllocString(L"TestProperty");

    hres = pNewClass->Put(
        KeyProp,
        0,
        NULL,
        CIM_STRING);

    IWbemQualifierSet* pQualSet = NULL;
    vVariant.vt = VT_BOOL;
    vVariant.boolVal = TRUE;
    hres = pNewClass->GetPropertyQualifierSet(KeyProp, &pQualSet);
    hres = pQualSet->Put(L"Key", &vVariant, 0);

    HANDLE hThread[2];
    DWORD dWResult1;
    DWORD dWResult2;
    hThread[0] = CreateThread(NULL, 0, ThreadProc1, NULL, 0, NULL);
    hThread[1] = CreateThread(NULL, 0, ThreadProc2, NULL, 0, NULL);

    WaitForMultipleObjects(2, hThread, true, INFINITE);
    GetExitCodeThread(hThread[0], &dWResult1);
    GetExitCodeThread(hThread[1], &dWResult2);
    printf("Thread execution completed \n");
    getchar();
    CloseHandle(hThread[0]);
    CloseHandle(hThread[1]);
    SysFreeString((BSTR) KeyProp);//add

    printf("Breakpoint\n"); 
    
    return 0;
}