iOS app crash when trying to log NSDictionary

Question

I have a problem where I try to log NSDictionary content and as soon as the method is called the app crashes.

This is the code I have tried after advice from a talented "hacker":

%hook UserData
-(int)getVariable:(NSDictionary *)fp8 {

for (NSString *key in [fp8 allKeys]) {
%log(@"key: %@, value: %@ \n", key, [fp8 objectForKey:key]);

}
return %orig;
}
%end

also tried:

%hook UserData
-(int)getVariable {

int originalValue = %orig;

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;
NSError *error;

[[fp8 description] writeToFile:[NSString stringWithFormat:@"%@/lol_%d.txt",basePath,fp8.count] atomically:NO encoding:NSUTF8StringEncoding error:&error];

return %orig;

}

%end

Both ways result in a crash of the app. This is on a iphone 4 with ios 6.1.3 tethered JB.

 DoD EN[1000]: -[__NSCFConstantString allKeys]: unrecognized selector sent to instance 0x2a7a88
 DoD EN[1000]: *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFConstantString allKeys]: unrecognized selector sent to instance 0x2a7a88'
    *** First throw call stack:

Does anyone have a suggestion on what may be wrong here?

On what line does the app crash? What is the error reason given for the crash (EXEC_BAD_ACCESS? Something else?) Also, what are the "%" signs in your code supposed to represent? I've never seen that before in this context. — user1118321, Nov 29 '13 at 19:26
And note that you're not logging an NSDictionary, but rather an entry from one. — Hot Licks, Nov 29 '13 at 22:23
The app crash after the dylib that is compiled with this hook of the getVariable function is loaded. The % signs is from theos — user2700999, Nov 30 '13 at 09:25
just some good-natured advice: you dabble in things you don't get .. very basic things. before trying stuff like hooking into other apps Id ask you to start with the basics — Daij-Djan, Nov 30 '13 at 12:22

Olotiar · Answer 1 · 2013-11-30T12:09:10.463

The crash log provide quite an explanation

-[__NSCFConstantString allKeys]: unrecognized selector sent to instance 0x2a7a88

I guess this is the crash log associated with the first piece of code you posted :

%hook UserData
-(int)getVariable:(NSDictionary *)fp8 {

    for (NSString *key in [fp8 allKeys]) {
        %log(@"key: %@, value: %@ \n", key, [fp8 objectForKey:key]);
    }
    return %orig;
}
%end

It crashes at the execution of [fp8 allKeys], claiming that allKeys is not a valid selector for objects of class __NSCFConstantString What it tells you is that fp8 is not an NSDictionary* but rather a __NSCFConstantString* (that is, a pointer to a constant instance of NSString such as one defined like NSString* foo = @"bar").

If that is true, then the second code you posted would crash also because count is not a valid selector for class NSString.

Why don't you just try the following, see what it gives you :

%hook UserData
-(int)getVariable:(id)fp8 {

    %log(@"fp8: %@ : %@\n", NSStringFromClass([fp8 class]), [fp8 description]);

    return %orig;
}
%end

Glad I could help. In that case, you might wanna mark the above answer as accepted. Out of curiosity : what are you trying to do swizzling those methods ? — Olotiar, Dec 02 '13 at 07:54

score 0 · Answer 2 · edited Nov 30 '13 at 09:58

0

If you print the description it should work. Following Way :

NSLog(@"%@", [dictionary description]);

edited Nov 30 '13 at 09:58

Divya Bhaloidiya

5,018
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answered Nov 29 '13 at 19:36

Raphael Oliveira

7,751
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Not sure how to use this info, sorry for being unclear. The code above is a hook into a function of a app I dont have the sourcecode for. Its reverse engineering so to speak. – user2700999 Nov 30 '13 at 09:35

iOS app crash when trying to log NSDictionary

2 Answers2