I've set up an Exception Breakpoint in XCode 4. Will it break for exceptions that originate within the Cocoa Touch framework AND are handled by the framework? I.E. Will the debugger stop for all exceptions, even if they are a natural part of the framework and handled by it internally?
My debugger keeps halting for a seemingly harmless exception from deep down in the framework and I need to know if I can safely ignore it.
If you're like me, there are times you want to ignore particular exceptions (like Apple's intermittently buggy CMMThrowExceptionOnError, which Apple neglects to provide any feedback to my bug reports for months)
So, my not-very-efficient solution is to add the following breakpoint instead of 'Add C++ Exception Breakpoint...'
from gdb command line, enter
break __cxa_throw
Then, in the XCode breakpoints editor, add the following 'Debugger Command' to this breakpoint. By substituting the offending address of $eip, you can exclude individual
exceptions from your breakpoint.
silent
# go up one stack frame silently
up-silently
# in my particular app, address of CMMThrowExceptionOnError is 0x9704d22e
if ( $eip == 0x9704d22e )
# echo gdb ignore exception\n
#print $eip
cont
end
If you can devise a better solution which doesn't incur the overhead of a debugger script, please let me know.
The exception breakpoint is just that: a breakpoint for exceptions. This includes those within the framework. It doesn't matter whose exception it is - if it's raised, it should break.
Just a short note on LLDB used by defat in Xcode 4.3
Commands have a different syntax.
set $eip = xxxx
is now
reg write tip 0x006373ec
a full map of commands is available at http://lldb.llvm.org/lldb-gdb.html
Related
I am using the GHS MULTI Debugger to debug an integrity project for an embedded application. Does anyone know how to configure a stop on throw for this debugger like you can do in GDB? I want to have it break when an exception is thrown. (I know the majority of SO does not develop Integrity projects or use the MULTI debugger, but I thought I would throw this out there to see if any other Integrity developers might know).
For this example let's assume your Integrity project is named Test.gpj.
Before compiling your code, edit your Test.int file in a text editor and change the "StartIt" value to false. This will prevent the executable from starting immediately when it is loaded.
Then in the simulator (or on the target), when you load your executable, start debugging it with the Test_as0 file.
In the Multi Command line, enter:
e __throw
Set a breakpoint on the beginning of this function (set the breakpoint to be an any task break point).
Repeat this also for the __rethrow function.
Now, when an unhandled exception occurs when your executable is running, it will hit one of these break points. You can then navigate the call stack and see where this exception is occurring. (There is an option in the Debugger GUI to navigate up and down the stack frames). Alternatively you can enter:
Ctrl + + and Ctrl + - will navigate up and down the stack frames to find where the exception was encountered.
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
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.
Normally in Visual Studio, a watch cannot be evaluated unless the debugger is stopped at a breakpoint. Is there a trick or add-on to make Visual Studio evaluate a watch while the application is still running? For example, evaluate the watch every time execution passes a point in the code while it's still running and without changing the code to insert statements like Debug.WriteLine.
Not sure this is possible, but I thought I'd ask.
Yes, this is possible. Set a breakpoint at the location where you'd want to see the value. Right-click the breakpoint and choose "When Hit...". Tick "Print a message" and write an expression like { value }. The message is displayed in the Output window while your program runs.
I would do that using compiler directives.
#if DEBUG
Debug.WriteLine
#end if
No this is not possible to do. The evaluation feature in Visual Studio is a stack frame based mechanism. That is that every evaluation is done in the context of a given stack frame (as viewed through the stack window). When the program is running the set of stack frames is currently changing and hence it's not possible to do a stable evaluation.
Additionally there are other limitations in the CLR which prevent this from managed code. It's not possible for instance to execute a function unless the debugee process is in a very specific state.