Question

I have an app that, according to crash logs, is crashing on startup while checking if the user is logged into Facebook on the device. The problem is that I cannot reproduce this crash, and it happens on different devices. So far, I have only seen this crash in pre-iOS 6 operating systems. The earliest iOS supported by my app is 4.3.

Here is the code, if anyone can provide a clue as to why this method sometimes fails (and most times does not!)

The error I get is EXC_BAD_ACCESS (SIGSEGV);KERN_INVALID_ADDRESS at 0x00000000.

    + (BOOL)loggedIntoServiceOnDevice:(int)socialService {

        __ENTERING_METHOD__
        BOOL loggedIntoServiceOnDevice = NO;
        ACAccountStore *accountStoreHere = [[NSClassFromString(@"ACAccountStore") alloc] init];
        ACAccountType *accountType;
        ACAccountType *accountType2;

        if (accountStoreHere) {
            if (socialService == FACEBOOK_SERVICE) {

                ACAccountType *accountType = [accountStoreHere accountTypeWithAccountTypeIdentifier:@"com.apple.facebook"];
                Class slComposeController = NSClassFromString(@"SLComposeViewController");
                if (accountType && slComposeController != nil)
                {
                    if ([SLComposeViewController isAvailableForServiceType:SLServiceTypeFacebook]) {

                         loggedIntoServiceOnDevice = YES;
                    }
                }
            }
            else if (socialService == TWITTER_SERVICE) {
                ACAccountType *accountType = [accountStoreHere accountTypeWithAccountTypeIdentifier:ACAccountTypeIdentifierTwitter];
                if (accountType)
                {
                    Class slComposeController = NSClassFromString(@"SLComposeViewController");
                    if ([TWTweetComposeViewController canSendTweet] || slComposeController != nil) {
                        if ([SLComposeViewController isAvailableForServiceType:SLServiceTypeTwitter]) {

                            loggedIntoServiceOnDevice = YES;
                        }
                    }
                }
            }
        }
        [accountStoreHere release];
        return loggedIntoServiceOnDevice;
    }

Answer 1

The following line is also executed in iOS 5 since [TWTweetComposeViewController canSendTweet] is returning YES so the second part of the OR check is not evaluated, since the first one already returned YES:

[SLComposeViewController isAvailableForServiceType:SLServiceTypeTwitter]

You might want to change those if statements to something like:

if ([TWTweetComposeViewController canSendTweet] ||
    (
     slComposeController != nil &&
     [SLComposeViewController isAvailableForServiceType:SLServiceTypeTwitter]
    )
   ) {

This makes sure, that SLComposeViewController is only used, if the class actually exists.