How to know which line is causing exception?

Question

I am new to XCode and Objective C. I have intentionally make a mistake to assign number to NSString*.

NSString* s = @1;
[s uppercaseString];

Though XCode gives me warning, this code will compile. But at runtime I get exception. Now I see in logs, (Sorry for image, I was not able to paste is as text properly due to formatting)

In this log, how I find exact place of error. How this log tells me which code to change.

Answer 1

To understand what line causes the problem, you usually need to add exception breakpoint to your project as explained in this document;

1. In the bottom-left corner of the breakpoints navigator, click the Add button.
2. Choose Add Exception Breakpoint.
3. In the Exception pop-up menu, choose the type of exception on which you want execution to stop:
   • All. Stops on all exceptions.
   • Objective-C. Stops on Objective-C exceptions.
   • C++. Stops on C++ exceptions. To stop on a particular C++ exception, specify the exception name.
4. Choose the phase of the exception handling process at which you want program execution to stop.
5. Click Done.

Answer 2

So it looks like you are running the Release build (debug symbols stripped) and if you got that crash log in a production environment you would need to symbolicate it in order to find the line.

This Apple TN gives some details of Symbolication.

In a development environment you would simply add an exception breakpoint and run it from Xcode, as the debug symbols would not be stripped.

Answer 3

line 5 Sam : [BIDViewController viewDidLoad] + 143 , if this is a release build , you need to resolve with symbols the memory address of the function , this is called "symbolize" the crash dump...

Answer 4

In the log look for your project name and you will come to know.

e.g.

line 5 Sam : [BIDViewController viewDidLoad] + 143 

If you want to produce real crash without warning, try following code it will produce index out of bound exception and will crash

NSArray *array = @[@"1",@"2"];
NSLog(@"Item not accessible->%@",(NSString*)array[2]);

Answer 5

set Exception breaking point or enable NSZombie object

or

NSZombie

From the menu bar, choose Project > Scheme > Edit Scheme