HDC内存泄漏(释放HDC/删除HDC）

HDC memory leak (release HDC/ delete hdc)

本文关键字：HDC 删除 内存 泄漏 释放      更新时间：2023-10-16

我遇到HDC内存泄漏的问题。你们能检查一下我是否正确发布/删除HDC吗？

谢谢！

BITMAP bm;
HBITMAP hbmap;
HBITMAP hBitmapOld;
BITMAPINFO bmi;
HDC hdcShot;


while(true)
{
    if (!TakeScreenshot(GameWindow, bm, hbmap, bmi, hdcShot, hBitmapOld, appWnd))
                    break;
        HBITMAP hbmapNew = CreateCompatibleBitmap(hdcShot, rcWindow.right - rcWindow.left, rcWindow.bottom - rcWindow.top);
        HDC hdcShotNew = CreateCompatibleDC(hdcShot);
        HBITMAP OldBmp = (HBITMAP)SelectObject(hdcShotNew, hbmapNew);

        BitBlt(hdcShotNew, 0, 0, rcWindow.right - rcWindow.left/*Window WIDTH*/, rcWindow.bottom - rcWindow.top/*Window HEIGHT*/
            , hdcShot, 0, 0, SRCCOPY);

        pPixels = new RGBQUAD[bm.bmWidth * bm.bmHeight];
        if (!pPixels) return false;
        SelectObject(hdcShotNew, OldBmp);

        if (!GetDIBits(hdcShotNew, hbmapNew, 0, bm.bmHeight, pPixels, &bmi, DIB_RGB_COLORS))
        {
            DeleteDC(hdcShot);
            delete[] pPixels;
            return false;
        }

// dont mind about this
        ScanContents scanContentsMain(bm, rcWindow, pPixels);
// dont mind about this
        ScanBMPHorizontal(&scanContentsMain);


        //free memory - I might have cleared the memory incorrectly here! Please check!
        free(pPixels);
        SelectObject(hdcShot, hBitmapOld);
                DeleteDC(hdcShot);
                DeleteObject(hbmapNew);
                DeleteDC(hdcShotNew);
}

TakeScreenShot Func（不是很重要，但它显示了一些变量是如何初始化的）

    bool TakeScreenshot(std::string WindowToFind, BITMAP &bm, HBITMAP &hbmap, BITMAPINFO &bmi, HDC &hdcShot, HBITMAP &hBitmapOld, HWND &hwnd)
{
    RECT rc;
    GetWindowRect(hwnd, &rc);
    hdcShot = CreateCompatibleDC(0);
    hbmap = CreateCompatibleBitmap(GetDC(0), rc.right - rc.left/*Window WIDTH*/, rc.bottom - rc.top/*Window HEIGHT*/);
    SelectObject(hdcShot, hbmap);

    BitBlt(hdcShot, 0, 0, rc.right - rc.left/*Window WIDTH*/, rc.bottom - rc.top/*Window HEIGHT*/
        , GetDC(0), rc.left, rc.top, SRCCOPY);
//Ignore this
    if (!GetObject(hbmap, sizeof(BITMAP), (LPSTR)&bm))
        return false;
    int bitsPerPixel = bm.bmBitsPixel;

 //Ignore this  
    if (bitsPerPixel != 32 || bm.bmPlanes != 1)
        return false;
//Don't mind about this too much 
    SetupBitmapInfo(bmi, bm.bmWidth, bm.bmHeight, bitsPerPixel);

    return true;
}

我向删除者核实了一下，发现我正在与HDC泄漏作斗争。我不确定我做错了什么。

此处存在资源泄漏：

hbmap = CreateCompatibleBitmap(GetDC(0), rc.right - rc.left, rc.bottom - rc.top);

你应该换成

HDC hdc = GetDC(0);
CreateCompatibleBitmap(hdc, rc.right - rc.left, rc.bottom - rc.top);
... 
ReleaseDC(0, hdc);//call this before exiting the function

free(pPixels)是错误的（尽管在这种情况下它仍然可以清除）。用delete[]pPixels 替换free(pPixels)

更改此项：

SelectObject(hdcShot, hBitmapOld);
DeleteDC(hdcShot);
DeleteObject(hbmapNew);
DeleteDC(hdcShotNew);

对此：

SelectObject(hdcShot, OldBmp);
DeleteObject(hbmapNew);
DeleteObject(hBitmapOld);
DeleteDC(hdcShot);
DeleteDC(hdcShotNew);
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