IOS：坠毁在64位设备 [英] ios:crash in 64 bit device

问题描述

有人能解释为何我的应用程序崩溃，并显示以下错误：

Can someone explain why my app crashes with the following error:

EXC_BAD_ACCESS（code = 1，地址= ...）

EXC_BAD_ACCESS(Code = 1, address= ...)

此崩溃只发生在64位器件。我无法找到答案。

This crash occurs only in 64 bit devices. I am not able to figure it out.

  - (NSString *)getIPAddress
    {
        NSString *address = nil;
        struct ifaddrs *interfaces = NULL;
        struct ifaddrs *temp_addr = NULL;
        int success = 0;

        // retrieve the current interfaces - returns 0 on success
        success = getifaddrs(&interfaces);
        if (success == 0)
        {
            // Loop through linked list of interfaces
            temp_addr = interfaces;
            while(temp_addr != NULL)
            {
                if(temp_addr->ifa_addr->sa_family == AF_INET)// crashes here
                {
                    // Check if interface is en0 which is the wifi connection on the iPhone
                    if([[NSString stringWithUTF8String:temp_addr->ifa_name] isEqualToString:@"en0"])
                    {
                        // Get NSString from C String
                        address = [NSString stringWithUTF8String:inet_ntoa(((struct sockaddr_in *)temp_addr->ifa_addr)->sin_addr)]; // crash also here
                    }
                }
                temp_addr = temp_addr->ifa_next;
            }
        }
        // Free memory
        freeifaddrs(interfaces);
        return address;
    }

谢谢！

推荐答案

按照<一个href="https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man3/getifaddrs.3.html"相对=nofollow>文档：

的ifa_addr字段引用任接口的地址或   的链路层地址        接口，如果存在，否则它为NULL。 （该ifa_addr字段的上sa_family字段应        协商，以确定所述ifa_addr地址的格式。）

The ifa_addr field references either the address of the interface or the link level address of the interface, if one exists, otherwise it is NULL. (The sa_family field of the ifa_addr field should be consulted to determine the format of the ifa_addr address.)

很可能有您的64位设备上的一个接口，它不具有 ifa_addr 字段填充。

It is likely there is an interface on your 64-bit device that does not have the ifa_addr field populated.

要解决您的问题，检查空 ifa_addr 。我还建议终止循环，因为你完成，一旦你找到 EN0 。

To fix your problem, check for a NULL ifa_addr. I also recommend breaking out of the loop since you are finished once you find en0.

...
while(temp_addr != NULL)
{
    if(temp_addr->ifa_addr != NULL && temp_addr->ifa_addr->sa_family == AF_INET)
    {
        // Check if interface is en0 which is the wifi connection on the iPhone
        if([[NSString stringWithUTF8String:temp_addr->ifa_name] isEqualToString:@"en0"])
        {
            // Get NSString from C String
            address = [NSString stringWithUTF8String:inet_ntoa(((struct sockaddr_in *)temp_addr->ifa_addr)->sin_addr)];
            break;
        }
    }
    temp_addr = temp_addr->ifa_next;
}
...

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