Im using XCode 4 and seeing a problem with debugging that did not exist in 3.x.
I am putting a breakpoint at a line where I call an object method.
Product *p = [[Product alloc] init];
[p print]; <-- Put a breakpoint here
After control stops at that line, I try to step into the method (F7). But nothing happens. System just skips over the line and goes to the next line (same behavior as Step Over).
Step into works fine for plain C language projects. The problem is with Objective-C methods. How do I fix this problem? Thanks.
Not sure if this will help -- Go into system preferences, and under the Keyboard general settings ensure that the "Use all F1 F2 etc. as standard function keys" option is checked.
F7 started to work for me after I checked that.
Hope that helps...
Check that the instance is not nil before trying to step into it's instance method. As embarrassing as it may seem, we all do it occasionally.
Stepping into ObjC method calls is not always possible. The way it was explained to me, there are internal runtime data structures that must be in a consistent state in order to reliably step into an ObjC method. If those internals happen to be in an inconsistent state when the program stops at your breakpoint, stepping in in the debugger will fail, and it will step over the call instead. This was also true in Xcode 3, and really has little or nothing to do with Xcode, but is an ObjC runtime and debugger issue. I estimate anecdotally (working in Xcode full-time for 3+ years) that stepping into an ObjC method call fails ~5% of the time. I find that it happens most often when it will be the most inconvenient to me. :)
That said, if you're NEVER able to step into ANY ObjC method call, then there's likely another problem, as I've been able to step into ObjC method calls many times with Xcode 4, and don't see this problem any more or less often than I did with Xcode 3.
fn+f7 always works for me. Although step into in Obj-C is kinda weird from time to time. You'd better set more breakpoints if you know where the code is heading.
I don't know enough about OSX to understand why this is fubar but I just tried changing the default key bindings to f13-f17 for all the usual bindings of pause/continue, step into/out of etc. Works for me. Pretty sucky QA on the XCode4 team possibly?
Switching to the gdb debugger works for me. Go to Edit Schemes, the Info tab for the Run phase, change from LLDB to GDB.
It's still not perfect. In particular it seems you have to use "Step into instruction" (with the appropriate key, or holding ctrl while hitting the step button) a lot if nothing happens, and to see registers and so on you have to use the gdb command line within the Xcode windows.
Remove the particular file and add the file again. This fixes my problem.
Related
I don't know what has changed on my setup, but it used to be that when my (Swift) code crashed, the debugger would show the offending line of source code.
Now no matter what the problem is, the debugger only highlights the line in AppDelegate.swift where UIApplicationMain is defined.
I can tell by putting in print statements more or less where in the code the problem arose, however... what's the point of having a debugger if it never conveys any information and I just have to do everything "old school" with print statements -- especially if there are asynchronous processes going on in which the print statement isn't necessary a reliable indicator of where the crash occured?
I've seen threads from years ago that talk about going into "Preferences -> Behaviors" and modifying what gets shown when the code exits unexpectedly. But (a) I never needed this in the past, and more importantly (b) this seems to have no effect, i.e. the debugger is still just quitting on main.
Is there a good way to get the old, specific, debugging behavior back?
I'm currently running Xcode 7.0, but this behavior occurs with 7-GM Seed, and even now when I go back to try 7 beta 5 and beta 6, which used to work.
Go to the Debug Navigator (cmd-7), click the plus button in the bottom and select Add Exception Breakpoint. This will break at the actual line where the problem happened.
In the exception breakpoints detail editor create debugger command action and in the text box enter po $arg1. This will show the error message in the debug console.
The previous answer was on the right track, but this answer is more relevant today:
On Xcode 9.2 with Swift 4, do this:
Use Command-8 to bring up the Debug Navigator.
Click the + in the lower left
Select Swift Error Breakpoint
That's it! :)
It's been bothering me since Xcode 6, that whenever I set 'All Exceptions' without any other breakpoints, Xcode would stop at start when I init a UILabel view wrapper in RootVC.
If I try to remove the causing line, another "random" line would trigger it again. Thoughts on what caused the exception?
This breakpoint comes from an exception that was thrown by TFileDescriptorContext. All Exceptions halts also on C++ exceptions.
It gives you a good indication where the problem comes from. Take a look if all fonts that are listed in Info.plist are part of your application bundle.
"Normally" you are not interested in C++ exceptions when you are in Objective-C, so feel free to ignore them.
Edit: This problem has been discussed several times here on SO. Updating when I can find the posts again which might give you even a deeper insight.
Where XCode generate error for application crash ?
I'm crazyng ! My application when open second file xib with webview then it crash. But I don't know why ? how can i Know where is error ?
You need to learn how to use the debugger in Xcode.
Run your app under the debugger then instead if simply getting a stack trace Xcode will stop at the line the fault occurs and show you your code and variables. You can then examine the contents of your variables, the call tree, etc. and hunt down the problem.
Once you know the general area of the problem you can place breakpoints to pause your application before the problem occurs and check whether your variables have the values expected etc. Then you can run till the next breakpoint, or step through your code a line at a time.
You can add code, such as NSAssert's and NSLog's to your app to check progress and display information without stopping the run, etc.
It's a process, and some problems will be harder to track down, but you'll get quicker at it with practice.
The Xcode documentation will tell you all about the debugger.
HTH
Sometimes when I press the "step into" button in the Xcode debugger, it instead steps over the method call.
This happens even though the method is a method I wrote, and the source code is in the same project.
Can anyone explain how to prevent this?
This may also happen when the method is being called on a nil object.
From Apple's developer docs:
A nil value is the safest way to initialize an object pointer if you don’t have another value to use, because it’s perfectly acceptable in Objective-C to send a message to nil. If you do send a message to nil, obviously nothing happens.
This is not necessarily so obvious if you've used pretty much any other language, because they largely don't include this "feature."
I have had issues with LLDB. Switching to GDB corrected this. Product->Edit Scheme->Run->Debugger.
You may need to Clean your targets in XCode. Under the Build menu try Cleaning All and see if that resolves your issue.
I'm not sure if this is possible. Here is an example situation:
Something is printing to my console and I don't know where it is coming from in the code. I did a quick search using the Finder in Xcode on terms such as 'NSLog' and 'print'. Nothing relevant came up.
Is there any quick way that Xcode has of finding where the source of the output is coming from ?
Kind of like when you right click on a method and you have all the options of exploring different parts of the code associated with that method.
Also: are there other functions that print besides NSLog and print?
Thanks so much!
Try running in the debugger, with breakpoints set on printf, NSLog, etc. When you hit a breakpoint do a backtrace (bt) to see where it's being called from
There's a plugin LinkedLog for that. You replace all NSLogs with LLogs and then will be able to just tap on link in Xcode's console to get to the line caused it to appear.
Didn't try it myself, but definitely will.