objective-c - iPhone 泛洪内存泄漏

Question

我正在用 C 语言为 iPhone 实现一个 floodfill 函数。

填充有效，尽管我遇到了 2 个问题。

1. 执行几次以下代码后，手机会发出内存警告。最有可能是内存泄漏。另请注意，unsigned char *data (图像数据)在洪水填充结束时被释放。

2. (较小的问题)如果我尝试将 RGB 颜色写入大于大约 (r:200,g:200,b:200,a:200 ) 我遇到了奇怪的现象。解决此问题的方法是简单地限制值。

我怀疑这两个问题之间可能存在关联。

下面的代码使用堆栈描述了我的洪水填充算法:

.h:

typedef struct {
    int red;
    int green;
    int blue;
    int alpha;
} GUIColor;


struct pixel_st {
    int x;
    int y;
    struct pixel_st *nextPixel;
};
typedef struct pixel_st pixel;

.m:

   void floodFill(CGPoint location, GUIColor tc, GUIColor rc, size_t width, size_t height, unsigned char *data){
    if (isGUIColorEqual(tc, rc)) return;

    pixel* aPixel = (pixel *) malloc(sizeof (struct pixel_st));
    NSLog(@"sizeof aPixel : %i",(int)sizeof(aPixel));

    (*aPixel).x = location.x;
    (*aPixel).y = location.y;
    (*aPixel).nextPixel = NULL;

    int i = 0;

    NSLog(@"Replacement color A%i, R%i, G%i, B%i",rc.alpha,rc.red,rc.green, rc.blue);

    while (aPixel != NULL){
        pixel *oldPixel_p = aPixel;
        pixel currentPixel = *aPixel;
        aPixel = currentPixel.nextPixel;


        //Now we do some boundary checks
        if (!isOutOfBounds(currentPixel.x, currentPixel.y, width, height)){
            //Grab the current Pixel color
            GUIColor currentColor = getGUIColorFromPixelAtLocation(CGPointMake(currentPixel.x, currentPixel.y), width, height, data);

            if (isGUIColorSimilar(currentColor, tc)){
                //Colors are similar, lets continue the spread
                setGUIColorToPixelAtLocation(CGPointMake(currentPixel.x, currentPixel.y), rc, width,height, data);

                pixel *newPixel;


                if ((newPixel = (pixel*) malloc(sizeof(struct pixel_st))) != NULL) {
                    (*newPixel).x = currentPixel.x;
                    (*newPixel).y = currentPixel.y-1;
                    (*newPixel).nextPixel = aPixel;
                    aPixel = newPixel;

                }
                if ((newPixel = (pixel*) malloc(sizeof(struct pixel_st))) != NULL) {
                    (*newPixel).x = currentPixel.x;
                    (*newPixel).y = currentPixel.y+1;
                    (*newPixel).nextPixel = aPixel;
                    aPixel = newPixel;
                }
                if ((newPixel = (pixel*) malloc(sizeof(struct pixel_st))) != NULL) {
                    (*newPixel).x = currentPixel.x+1;
                    (*newPixel).y = currentPixel.y;
                    (*newPixel).nextPixel = aPixel;
                    aPixel = newPixel;
                }
                if ((newPixel = (pixel*) malloc(sizeof(struct pixel_st))) != NULL) {
                    (*newPixel).x = currentPixel.x-1;
                    (*newPixel).y = currentPixel.y;
                    (*newPixel).nextPixel = aPixel;
                    aPixel = newPixel;
                }
                free(oldPixel_p);
                i ++;
                if (i == width * height * 4 * 5) break;

            }


        }
    }

    free(aPixel);
}

此堆栈的实现基于此处找到的 ObjFloodFill:

https://github.com/OgreSwamp/ObjFloodFill/blob/master/src/FloodFill.m

Answer 1

首先，循环内的每个 if ((newPixel = (pixel*) malloc(...) 都会分配新的内存块，因此，您有 4 次分配在循环内并且仅1释放。

其次，我不明白为什么不简单地使用堆栈上的对象？您真的需要在堆上分配newPixel、oldPixel等吗？检查实现，可能有更简单的方法来实现相同的功能，而且根本不需要管理内存问题。