(NSDictionary *) labelAttrs = 0x00000001

Question

Doing some debugging I printed out the description of an NSDictionary variable which gives this:

(NSDictionary *) labelAttrs = 0x00000001

Can someone clarify why this is 1?

I'd understand nil or an object pointer but why 1?

UPDATE

The code:

NSDictionary *labelAttrs = @{NSForegroundColorAttributeName:[UIColor darkGrayColor]};

It crashes when run on iOS5 but not iOS6 but this:

Are the new object literals backwards compatible with iOS 5?

seems to say that you can use the new literals with iOS5 (as long as you build against iOS6 and use Xcode >= 4.5 and compile with latest LLVM - e.g see screen grab). And, according to Apple, I should be OK to use them: https://developer.apple.com/library/ios/#releasenotes/ObjectiveC/ObjCAvailabilityIndex/index.html

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Here's how it looks in Xcode before:

enter image description here

Then when I Step over:

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Note: this gives me the same crash:

NSDictionary *labelAttrs = [NSDictionary dictionaryWithObjectsAndKeys:[UIColor darkGrayColor], NSForegroundColorAttributeName, [UIFont fontWithName:CUSTOMFONT size:size], NSFontAttributeName, [NSNumber numberWithInt:0], NSStrokeWidthAttributeName, nil];

Removing this (and the following 2 lines of code) means the app runs without crashing. But obviously no attributed strings.

UPDATE: resolved. Attributed strings aren't available on iOS5 (at least for UILabel's): Is NSAttributedString available before iOS 6?

It's pretty strange, usually the lowest memory addresses are reserved to the OS. — Ramy Al Zuhouri, Mar 19 '13 at 16:15
http://stackoverflow.com/questions/9482689/uiviewcontroller-subclass-cant-assign-instance-variable — meth, Mar 19 '13 at 16:30
It indicates that you most likely stored the value 1 there, or incremented a nil pointer. Could also happen, though, if the location where the pointer is stored is garbage. — Hot Licks, Mar 19 '13 at 16:32
(Search back through your code and find out where the value is getting set. That will probably get you closer to your bug.) — Hot Licks, Mar 19 '13 at 16:34
(OTHO, if it is a local (method) variable, and it has not yet been assigned in the method, it could be "perfectly normal garbage".) — Hot Licks, Mar 19 '13 at 16:36
Where does it crash? On that assignment or later when the dictionary is referenced? — Hot Licks, Mar 19 '13 at 17:49
So you're taking the hit on the assignment -- the variable is never properly assigned, and the "1" is likely just left-over garbage in that location. Your real problem is that the @ expression is crashing. — Hot Licks, Mar 19 '13 at 17:55
(IMO, the "@" expression stuff is not quite ready for prime time. Rather than wasting any more energy on it, why not just use `dictionaryWithObjectsAndKeys` and move on?) — Hot Licks, Mar 19 '13 at 17:57
Just tried dictionaryWithObjectsAndKeys and get the same problem. — Snowcrash, Mar 19 '13 at 18:02
Is CUSTOMFONT valid? (Start with an empty list -- just the nil -- and add one pair at a time until it breaks.) — Hot Licks, Mar 19 '13 at 18:14
(And keep in mind that attributed strings in labels are not supported in iOS 5.) (Though this would have nothing to do with the creation of the dictionary failing.) — Hot Licks, Mar 19 '13 at 18:21
@HotLicks doh! that's the problem. Awesome job - thanks. Pop that down in an answer. — Snowcrash, Mar 19 '13 at 18:24
But that should not, by itself, prevent the creation of the dictionary from failing. The dictionary has no idea that its destined to be used for an attributed string. — Hot Licks, Mar 19 '13 at 18:27

Hot Licks · Accepted Answer · 2013-03-19T19:46:43.823

The problem is that the NSAttributedString UIKit additions is not available until iOS 6. This means that the constants NSForegroundColorAttributeName et al are not defined. So the creation of the dictionary blows up trying to reference these.

(The way to debug this -- short of checking the reference for the wrong iOS version (;)) -- is to break up the statement:

UIColor* value1 = [UIColor darkGrayColor];
NSString* key1 = NSForegroundColorAttributeName;
UIFont* value2 = [UIFont fontWithName:CUSTOMFONT size:size];
NString* key2 = NSFontAttributeName;
NSNumber* value3 = [NSNumber numberWithInt:0];
NSString* key3 = NSStrokeWidthAttributeName;

NSDictionary *labelAttrs0 = [NSDictionary dictionaryWithObjectsAndKeys:nil];
NSDictionary *labelAttrs1 = [NSDictionary dictionaryWithObjectsAndKeys:value1, key1, nil];
NSDictionary *labelAttrs2 = [NSDictionary dictionaryWithObjectsAndKeys:value2, key2, nil];
NSDictionary *labelAttrs3 = [NSDictionary dictionaryWithObjectsAndKeys:value3, key3, nil];

Then see what fails. In this case you probably would have gotten a failure on assigning labelAttrs1. If you then were to NSLog value1 and key1 you would have gotten an error on key1.)

score 0 · Answer 2 · answered Mar 19 '13 at 16:26

0

0x00000001 indicates an invalid memory address. What version of Xcode are you using? You may need to switch from lldb to gdb

answered Mar 19 '13 at 16:26

JoeCortopassi

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score 0 · Answer 3 · answered Mar 19 '13 at 16:34

0

I have seen 0x00000001 in lldb when im stepping through code like this:

labelAttrs = [self someMethod];

If you print labelAttrs, before having evaluated the -someMethod, then it will be assigned to 0x00000001.

answered Mar 19 '13 at 16:34

neoneye

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(NSDictionary *) labelAttrs = 0x00000001

3 Answers3