c++ - Microsoft 的 WMI 库中的内存泄漏。有没有办法减轻它？

Question

当我们使用 IWbemQualifierSet::Put 将 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办。

有没有什么方法可以通过操纵调用堆栈来缓解它？或者通过在某种隔离容器中为类预分配内存以确保在类对象被销毁后完全释放它？

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

更新:即使我们在循环中创建和销毁类对象，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 4000 字节长或 1 字节长的字符串，泄漏的内存量也是一样的。

主要.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，发现内存占用确实从任务管理器一直在增加。并不断地展示这一点。

我在“for”循环中添加了Sleep(50);，“抛出异常......”消失了。但内存占用仍在增加。进程内存在 6 分钟内增加到 565MB。

“for”循环与 Put(pKey, &value, 0) 之间存在冲突；

所以，使用多线程是必要的。

我修改了代码，运行良好。对循环和进程内存没有影响是正常的。

代码如下，还有很多瑕疵，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;
}