CFString 内存泄漏 [英] CFString memory leak

问题描述

我已将内存泄漏范围缩小到以下代码

I have narrowed down a memory leak to the following code

CFStringRef CFDataToString(CFDataRef data)
{
    UInt8* buf = malloc(CFDataGetLength(data));

    CFDataGetBytes(data, CFRangeMake(0, CFDataGetLength(data)), buf);

    CFMutableStringRef output = CFStringCreateMutable(kCFAllocatorDefault, CFDataGetLength(data) * 2);

    for(int i = 0; i < CFDataGetLength(data); i++) {
        CFStringAppendFormat(output, NULL, CFSTR("%02x"), buf[i]);
    }

    free(buf);
    CFRelease(data);

    return output;
}    

以下是上下文中使用的代码，为了演示，已经简化了一些方法.Instruments 报告了 CFStringCreateMutable 和 CFStringAppendFormat 的内存泄漏.

Below is the code used in context, some methods has been simplified for demonstration. Instruments is reporting a memory leak of CFStringCreateMutable and CFStringAppendFormat.

CFStringRef CFDataToString(CFDataRef data)
{
    UInt8* buf = malloc(CFDataGetLength(data));

    CFDataGetBytes(data, CFRangeMake(0, CFDataGetLength(data)), buf);

    CFMutableStringRef output = CFStringCreateMutable(kCFAllocatorDefault, CFDataGetLength(data) * 2);

    for(int i = 0; i < CFDataGetLength(data); i++) {
        CFStringAppendFormat(output, NULL, CFSTR("%02x"), buf[i]);
    }

    free(buf);
    CFRelease(data);

    return output;
}    

CFDataRef hmac(CFStringRef key, CFStringRef data)
{
    const char *cKey  = CFStringGetCStringPtr(key, CFStringGetSystemEncoding());
    const char *cData = CFStringGetCStringPtr(data, CFStringGetSystemEncoding());
    unsigned char cHMAC[CC_SHA256_DIGEST_LENGTH];

    CCHmac(kCCHmacAlgSHA256, cKey, strlen(cKey), cData, strlen(cData), cHMAC);
    CFDataRef HMAC = CFDataCreate(kCFAllocatorDefault, cHMAC, sizeof(cHMAC));

    return HMAC;
}

CFDictionaryRef buildRequest(CFMutableDictionaryRef params)
{
    CFMutableStringRef signature = CFStringCreateMutable(NULL, 0);
    CFStringAppend(signature, CFDataToString(hmac(CFSTR("mykey"), CFSTR("mydata"))));

    CFDictionarySetValue(params, CFSTR("signature"), signature);


    // ....
    // ....       


    return params;
}

void request(CFMutableDictionaryRef params)
{
    params = buildRequest(params);

    // ... Run request

    CFRelease(params);
}

仪器输出...

推荐答案

再次作为答案.

使用 Create 方法分配的所有数据都负责将数据发布给程序员.在这方面，它与调用 malloc 相同.除非在文档中明确说明，否则任何方法都不会发布这些数据.

All data allocated with a Create method puts the responsibility for releasing the data to the programmer. In this regard, it's the same as calling malloc. No method will ever release this data, unless explicitely stated in the documentation.

要解决您的问题，请在接收它的方法中保存对已创建"(已分配)数据的引用，并在完成后在方法结束时释放它.

To solve your problem, save a reference to the 'Created' (Allocated) data in the method which receives it and release it at the end of the method, once you're done with it.

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