Remote Web Inspector Pt. 2
It gets even better, because this also works in Mobile Safari on the iOS 5 Simulator!
Here’s a little script you can run, that enables the remote Web Inspector via gdb (via @atnan).
Here’s to all the mobile devs!
Tagged: Debugging RSS Toggle Comment Threads | Keyboard Shortcuts
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Ullrich
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Ullrich
Remote Web Inspector
We recently stumbled across a blog post mentioning a way to enable a remote interface to a web inspector that is hidden inside the WebKit on iOS 5.
Here’s how it’s done. In your Application Delegate add the following code:
+ (void)initialize; { [NSClassFromString(@"WebView") performSelector:@selector(_enableRemoteInspector)]; }With this you can direct your browser to http://localhost:9999 to open the web inspector.
Have fun!
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Ullrich
Ullrich
Symbolicating without Xcode
Ever wanted to symbolicate a incomplete crash file (i.e. the logs you get from TestFlight)?
You can symbolicate individual addresses from the crashlog in the terminal using a command named `atos` (if you’ve got the dSYM file for your build). Here’s an example:
atos -arch armv7 -o MyApp.app.dSYM/Contents/Resources/DWARF/MyApp 0x0000babe
This will output you the line of code related to this address. I.e.:
+[MyHappyClass fullOfFail] (in MyApp) + 429
Pro Tip: not entering the address when calling the atos command leaves you in STDIN mode. Here you can add multiple addresses without restarting the tool.
Gernot
How to slow down Simulator Animations
There’s a new way to slow down simulator which is really handy in case you want to debug rotation animations:
- In the Hardware menu, enable “Simulate Hardware Keyboard”.
- Hit the shift key three times in a row
Now all the animations are slowed down for debugging. Triple-hit Shift again to deactivate.
Ullrich
Colliding Category Methods
After multiple years of Objective-C experience yesterday was the first time that we actually ran into problems with colliding methods in categories.
Here’s the story (you may skip this part): The issue was, that we added a method -setParameters: to NSMutableURLRequest which takes a dictionary and set’s it as query string or multipart form body depending on the HTTP Method used for sending the request. This method sadly conflicted with a category on the same class defined in a library called OAuthConsumer which doesn’t take a dictionary as argument but rather an array of key-value pairs. Both categories we’re linked to our application as static libraries.
The result was that our -setParameters: was called with an array although a dictionary was expected. We noticed the problem since NSArray is not responding to -allKeys. It could have gone would have not noticed the problem. Just imagine trying to debug a misbehavior when you’re looking at the wrong piece of code.
The quintessence, and what basically helped us finding the issue is a environment variable named OBJC_PRINT_REPLACED_METHODS. Similar to NSZombieEnabled you set it in the Arguments tab of your executable info as variable set to environment. Just like this:
Ullrich
Zombies
Everyone should know the NSZombieEnabled environment variable. Set it to YES to temporarily disable deallocation of objects which reach a retain count of zero. You then can set breakpoints to common methods such as:
fb -[_NSZombie init] fb -[_NSZombie retainCount] fb -[_NSZombie retain] fb -[_NSZombie release] fb -[_NSZombie autorelease] fb -[_NSZombie methodSignatureForSelector:] fb -[_NSZombie respondsToSelector:] fb -[_NSZombie forwardInvocation:] fb -[_NSZombie class] fb -[_NSZombie dealloc]
But you should also know that this only works on NS classes. To have a similar effect on CoreFoundation classes use CFZombieLevel. The value of CFZombieLevel is defined by a bit array. See the following table. A good value is 5 
Bit Action 0 scribble deallocated CF memory 1 when scribbling deallocated CF memory, don't scribble object header (CFRuntimeBase) 4 never free memory used to hold CF objects 7 if set, scribble deallocations using bits 8..15, otherwise use 0xFC 8..15 if bit 7 is set, scribble deallocations using this value 16 scribble allocated CF memory 23 if set, scribble allocations using bits 24..31, otherwise use 0xCF 24..31 if bit 16 is set, scribble allocations using this value
Ullrich
My list of breakpoints. Add them to your ~/.gdbinit
fb -[NSException raise] fb -[NSAssertionHandler handleFailureInFunction:file:lineNumber:description:] fb -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] fb NSKVODeallocateBreak fb _NSAutoreleaseNoPool fb -[_NSZombie init] fb -[_NSZombie retainCount] fb -[_NSZombie retain] fb -[_NSZombie release] fb -[_NSZombie autorelease] fb -[_NSZombie methodSignatureForSelector:] fb -[_NSZombie respondsToSelector:] fb -[_NSZombie forwardInvocation:] fb -[_NSZombie class] fb -[_NSZombie dealloc] fb szone_error fb objc_exception_throw fb malloc_error_break fb CGPostError fb malloc_printf fb _objc_error fb objc_exception_during_finalize_error fb auto_zone_resurrection_error fb auto_refcount_underflow_error
UPDATE: added _NSAutoreleaseNoPool breakpoint to stop when there’s no autorelease pool but one is expected.
Ullrich
Use NSAssert(…) during development.
But set NS_BLOCK_ASSERTIONS pre compiler flag for release.
toto is discussing. -
toto
NS_BLOCK_ASSERTIONS=1 Seems to be default in XCode 3.2
Ullrich
Optimize your Autorelease pools with the following environment variables
NSAutoreleaseHighWaterMark
Default: 0
If set to X, autorelease pools will print a message if more than X objects accumulate in the pool
NSAutoreleaseHighWaterResolution
Default: 0
If set to Y, a message is logged for every Y objects that accumulate in the pool beyond the high-water mark (X)
Ullrich
To put an application running in Simulator in slow motion mode press ` or + (for german or english keyboard layout)
UPDATE: Looks like this stopped working since some 3.1.x version. 
ANOTHER UPDATE: There is a new way to do this
Remember that this will influence you’re App Store review experience