存储在上下文中的对象的潜在泄漏答案

【问题标题】：Potential leak of object stored in context存储在上下文中的对象的潜在泄漏
【发布时间】：2015-04-29 20:38:28
【问题描述】：

这段代码出现内存泄漏。

- (CGContextRef) createARGBBitmapContextFromImage:(CGImageRef) imageRef {

    CGContextRef    context = NULL;
    CGColorSpaceRef colorSpace;
    void *          bitmapData;
    int             bitmapByteCount;
    int             bitmapBytesPerRow;

    // Get image width, height. We'll use the entire image.

    size_t pixelsWide = CGImageGetWidth(imageRef);
    size_t pixelsHigh = CGImageGetHeight(imageRef);

    // Declare the number of bytes per row. Each pixel in the bitmap in this
    // example is represented by 4 bytes; 8 bits each of red, green, blue, and
    // alpha.

    bitmapBytesPerRow   = (pixelsWide * 4);
    bitmapByteCount     = (bitmapBytesPerRow * pixelsHigh);

    // Use the generic RGB color space.
    colorSpace = CGColorSpaceCreateDeviceRGB();
    if (colorSpace == NULL)
    {
        fprintf(stderr, "Error allocating color space\n");
        return NULL;
    }
    // Allocate memory for image data. This is the destination in memory
    // where any drawing to the bitmap context will be rendered.
    bitmapData = malloc( bitmapByteCount );

    if (bitmapData == NULL)
    {
        fprintf (stderr, "Memory not allocated!");
        CGColorSpaceRelease( colorSpace );
        return NULL;
    }

    // Create the bitmap context. We want pre-multiplied ARGB, 8-bits
    // per component. Regardless of what the source image format is
    // (CMYK, Grayscale, and so on) it will be converted over to the format
    // specified here by CGBitmapContextCreate.

    context = CGBitmapContextCreate (bitmapData,
                                     pixelsWide,
                                     pixelsHigh,
                                     8,      // bits per component
                                     bitmapBytesPerRow,
                                     colorSpace,
                                     kCGImageAlphaPremultipliedFirst);
    if (context == NULL)
    {
        free (bitmapData);
        fprintf (stderr, "Context not created!");
    }

    CGRect rect = {{0,0},{pixelsWide, pixelsHigh}}; 

    //        
    //        // Draw the image to the bitmap context. Once we draw, the memory
    //        // allocated for the context for rendering will then contain the
    //        // raw image data in the specified color space.
    CGContextDrawImage(context, rect, self.CGImage); 

    // Make sure and release colorspace before returning
    CGColorSpaceRelease( colorSpace );

    return context;
}

错误：存储在上下文中的对象可能泄漏。

【问题讨论】：

标签： ios objective-c memory-leaks

【解决方案1】：

内存泄漏分析器使用方法的名称来确定返回对象的保留计数的变化。对于 Obj-C 方法，它记录在 Basic Memory Management Rules 中。它指出

您使用名称以“alloc”、“new”、“copy”或“mutableCopy”开头的方法创建对象（例如，alloc、newObject 或 mutableCopy）。

名称createARGBBitmapContextFromImage: 与该规则不匹配。相反，您应该将方法命名为 newARGBBitmapContextFromImage:。

将单词Create 添加到函数名中用于C 函数。

【讨论】：