Valgrind的無效讀取錯誤

我一直無法查明確切的原因我Valgrind的錯誤：Valgrind的無效讀取錯誤

==3868== Invalid read of size 2 
==3868== at 0x100001F1F: Shrinker::Execute() (in ./proj4B) 
==3868== by 0x1000029CD: Filter::Update() (in ./proj4B) 
==3868== by 0x100001819: Image::Update() const (in ./proj4B) 
==3868== by 0x10000299E: Filter::Update() (in ./proj4B) 
==3868== by 0x100001819: Image::Update() const (in ./proj4B) 
==3868== by 0x10000299E: Filter::Update() (in ./proj4B) 
==3868== by 0x100001819: Image::Update() const (in ./proj4B) 
==3868== by 0x10000299E: Filter::Update() (in ./proj4B) 
==3868== by 0x100001819: Image::Update() const (in ./proj4B) 
==3868== by 0x10000299E: Filter::Update() (in ./proj4B) 
==3868== by 0x100001819: Image::Update() const (in ./proj4B) 
==3868== by 0x10000299E: Filter::Update() (in ./proj4B) 
==3868== Address 0x100c12040 is 0 bytes inside a block of size 7,201,152 free'd 
==3868== at 0x10000D94F: free (in /usr/local/Cellar/valgrind/HEAD/lib/valgrind/vgpreload_memcheck-amd64-darwin.so) 
==3868== by 0x100001BD5: PNMreader::Execute() (in ./proj4B) 
==3868== by 0x100001954: Source::Update() (in ./proj4B) 
==3868== by 0x100001819: Image::Update() const (in ./proj4B) 
==3868== by 0x10000299E: Filter::Update() (in ./proj4B) 
==3868== by 0x100001819: Image::Update() const (in ./proj4B) 
==3868== by 0x10000299E: Filter::Update() (in ./proj4B) 
==3868== by 0x100001819: Image::Update() const (in ./proj4B) 
==3868== by 0x10000299E: Filter::Update() (in ./proj4B) 
==3868== by 0x100001819: Image::Update() const (in ./proj4B) 
==3868== by 0x10000299E: Filter::Update() (in ./proj4B) 
==3868== by 0x100001819: Image::Update() const (in ./proj4B)

我想這是因爲我在收縮器嵌套循環::執行（）和/或它的析構函數：

void Shrinker::Execute() { 
    int inWidth = 0, inHeight = 0, maxVal = 255; 
    int halfWidth = 0, halfHeight = 0; 

    inWidth = img1->GetWidth(); 
    inHeight = img1->GetHeight(); 

    halfWidth = inWidth/2; 
    halfHeight = inHeight/2; 

    buffer = (Pixel *) malloc(sizeof(Pixel)*halfWidth*halfHeight); 

    int in = 0, out = 0; 
    for (int i = 0; i < halfHeight; i++) { 
     for (int j = 0; j < halfWidth; j++) { 
      in = i*2*inWidth+j*2; 
      out = i*halfWidth+j; 
      buffer[out] = img1->GetPixels()[in]; 
     } 
    } 

    img.ResetSize(halfWidth, halfHeight); 
    img.SetMaxVal(maxVal); 
    img.SetPixels(buffer); 

} // end Shrinker::Execute()

我試圖盡一切小的調整我能想到的這兩個嵌套循環和收縮機malloc的，但無濟於事。它的析構函數釋放緩衝區並將其設置爲NULL。任何指導將不勝感激。

來源

2015-06-12 Dylan Secreast

顯示'Pixel'的定義。 'malloc'不應該在C++中使用，因爲它實際上並不開始具有不平凡構造函數的對象的生命週期 –

如果您懷疑析構函數問題，那麼顯示析構函數 –

來自Filter :: Update的地方很有用？也許錯誤進入'ResetSize'，'SetMaxVal'，或'SetPixels'或'GetPixels（）'，你沒有顯示這些代碼。例如，這可能是'GetPixels'中的緩衝區溢出。 –

其實，我不知道你的代碼的目的。但是，也許你使用下面的代碼錯誤的參數：

in = i*2*inWidth+j*2;

它應該是：

in = i*2*halfwidth+j*2;

我想。

來源

2015-06-12 03:45:27

不要認爲這是原因，它看起來像代碼產生一個傾斜的圖像，我仍然得到相同的valgrind錯誤。感謝您的輸入！ –

我在這裏猜測，但由於它進入一個以前已經free'd的塊 - 某些東西正在銷燬在Shrinker::Execute中分配的緩衝區 - 如果唯一一個free'd的地方是你的析構函數，那麼你可能是你的Shrinker創建了一個不好的（可能是臨時的）副本 - 例如，如果你從函數返回了一個Shrinker對象，就會發生這種情況。

您需要確保您已阻止副本獲得創建或正確實施副本構造函數和賦值運算符。

來源

2015-06-12 04:00:00

Valgrind的無效讀取錯誤

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