OOPS

Xcode 4.3 error message: NSAutoreleasePool is unavailable in main.m

Alex — Thu, 26 Apr 2012 17:53:47 +0000

Question: I am trying to create and run a PhoneGap HTML 5 application for iOS 5 but I am getting error message of ‘NSAutoreleasePool is unavailable: not available in automatic reference counting mode’ while building main.m. SDK: Xcode 4.3 Machine: iMAC with Lion.

Answer:

You enabled ARC in build settings but your code is not ready to use Automatic Reference Counting. If you use ARC you can’t get to autorelease pools directly. You must use @autoreleasepool blocks instead:

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// Old:
int main(int argc, char *argv[]) {
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
int retVal = UIApplicationMain(argc, argv, nil, @"AppDelegate");
[pool release];
return retVal;
}

// With ARC replace it with such a code:
int main (int argc, char * argv[]) {
int retVal;
@autoreleasepool {
retVal = UIApplicationMain(argc, argv, nil, @"AppDelegate");
}
return retVal;
}

In your code you can use the followings to be ready to handle both cases:

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// For example:
#if __has_feature(objc_arc)
self.window = [[UIWindow alloc] initWithFrame:screenBounds];
#else
self.window = [[[UIWindow alloc] initWithFrame:screenBounds] autorelease];
#endif

If you don’t want to use ARC, switch it off:
1. Find the Build Settings of your project
2. Search for ‘CLANG_ENABLE_OBJC_ARC’
3. Set it to NO.

HP 2820/2840 Print and Scan on Mac OS X Lion

Mike D. — Wed, 25 Apr 2012 23:42:00 +0000

Question: I upgraded my iMac from Snow Leopard to Lion. My HP Color Laserjet 2840 prints but I can’t scan from the device any longer. The HP Director is grayed out. I found your post about HP 2820 scanning with Snow Leopard. Do you have an update?

Answer: Previous post on how to force Mac OX X Snow Leopard to print and scan with HP 2820/2840 network printer is here: Scan and print with HP 2820/2840 on OS X (Snow Leopard)

In that post all the links and steps are valid for Lion. Be sure to follow these steps:

1. Get Apple printer drivers for Lion. If you don’t find it download from apple.com.

2. Find HP’s latest drivers. Check out this link for download: LJMFP28x0OSX10.5Update-v8.2.dmg.

3. Switch on your printer. Check out network connections. Install HP’s package and restart your machine.

4. Uninstall the HP 2820/2840 driver from your machine you have just installed. Find System Preferences -> Print & Scan -> Use – to remove driver from the list. Install the Apple’s printer package.

5. Use System Preferences or HP Setup Assistant to discover and/or configure your network printer. You may need to manually add your network printer. Quit from the Assistant. Open HP Director and check out configuration.

If you don’t find the HP Setup Assistant, use the following command in the Terminal Window:

1	sudo /Applications/HP\ LaserJet\ Software/HP\ Setup\ Assistant.app/Contents/MacOS/HP\ Setup\ Assistant

Xcode 4.2 with iOS 5 to test location services in simulator

Misa — Thu, 03 Nov 2011 02:33:35 +0000

Question: I’m an iPhone programmer and have a problem. I should test and debug my iPhone/iPad application with location services for different GPS positions and routes. Do you have a static library or module that produces GPS coordinates in the preset range?

Answer: You do not need GPS location simulator any longer. Since Xcode 4 and iOS 5 you can select from preset locations or add routes to your project while you’re running your simulated app. Visit Apple’s web site for details from here.

In Xcode 4.2, to preset a default location for your project, choose Product -> Edit Scheme – or from the scheme selector in the toolbar find Your project name > Edit Scheme… – and select the Run action. Click the Options tab. Allow Location Simulation and choose one city from the the drop-down list.

While testing your app in the iOS Simulator, you can select Product -> Debug -> Simulate Location from the menu bar and choose any point from the preset locations:

'iPhone 5.0' (aka iOS 5) location simulating in Xcode 4.2

Your options:

1. Preset a single Location in your Scheme.

2. Choose a Location from the Program -> Debug -> Simulate Location menu (see above), or

3. Choose a Location from the Debug Bar (see below). if you are not running iOS 5.0 or later, these options can’t be used. Switch to iPhone 5.0 Simulator to allow selection:

Choose a Location from the Debug Bar

4. Edit a GPX file and add it to your project to establish single or multiple custom waypoints. GPX (GPS eXchange Format) is an xml data format for exchanging GPS data between programs. You can add one or more GPX file to your project. These files look like:

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For: Cupertino.GPX:

Cupertino, USA

For: Munich.GPX:

Munich, Germany

You can edit and add it to your project like any other file(s) or resources:

Add your GPX file to your project

Trace EXC_BAD_ACCESS exception in iPhone app with Xcode 4

Alex — Thu, 01 Sep 2011 19:10:53 +0000

Question: Recently I upgraded my universal iPhone project to Xcode 4 and ran immediately into an EXC_BAD_ACCESS exception in my application when running on an iPad. My code runs without errors on iPhone. I don’t know where it has come from and how to find the source code line in error. My app quits without saying anything and the debugger jumps to the main.m module. Console messages do not help either.

Answer: EXC_BAD_ACCESS exceptions usually happen when your code wants to use objects that have already been released. When the error is caught, the call stack is usually has gone on vacation. This is the probable reason of the silent exit and the jump to the main.m as the last resort of your debugger.

There is a well known NSZombieEnabled environment variable that, when it’s enabled, leaves a dummy object behind for every deallocated object. It lets us trace released objects while chasing an EXC_BAD_ACCESS exception. When NSZombieEnabled is set to YES, the class of all deallocated objects is dynamically changed to _NSZombie. The memory region will never free, so NSZombieEnabled should not be left in place otherwise you will spend hours trying to find memory leaks. Do not forget to set its value to NO when you are ready.

Where and how to set NSZombieEnabled to YES in Xcode 4?

1. Go to your project in Xcode 4
2. Environment variables can be set up in the Scheme editor (find Product -> Edit scheme… in menu bar):

Set NSZombieEnabled to YES in Xcode 4

3. Name the variable as NSZombieEnabled and set its value to YES.
4. Run your app in Debug mode. You likely get a … message sent
to deallocated instance… message and the debugger stops at the line in error. This information leads to the problem.
5. When ready, disable NSZombieEnabled by changing YES to NO.

PS: I checked your code. You should apply retain property in your subclasses:

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@interface myNavigationBar : UINavigationBar {
UIImage *imageBackground;
}
@property (nonatomic, retain) UIImage *imageBackground;
...

@implementation myNavigationBar
@synthesize imageBackground;
...

Upgraded Xcode 4 constantly crashes when opening XIB file

Mike D. — Wed, 22 Jun 2011 16:05:47 +0000

Question: I have some “old” iPhone projects. Since I upgraded from Xcode 3.2 to Xcode 4 it constantly crashes when I open an XIB file. The same project builds without errors in Xcode 3. The error log message is: “Encountered multiple assertions. First assertion was: ASSERTION FAILURE…” and a long list of stack info.

Answer: Your project.xcodeproj package is probably corrupted. Try out some of or all of these steps:

1. Open your project.pbxproj file with TextEdit. It’s in the project.xcodeproj package. See #3 for instructions below. Search for null strings like this:

1	/* (null) in Resources */ = {isa = PBXBuildFile; };

Remove it.

2. Search for explicitFileType = file.xib; in the project.pbxproj file. If found replace it with lastKnownFileType to have a valid settings like this:

1	65A1D75E12CEB12A005BE04D /* SettingsAddressViewController.xib */ = {isa = PBXFileReference; lastKnownFileType = file.xib; path = SettingsAddressViewController.xib; sourceTree = ""; };

3. Remove inherited settings from your project.xcodeproj package:

- Close Xcode 4

- Open Finder and navigate to your project folder.

- In the context menu of project.xcodeproj file select Show Package Contents. How? Context menu => right click on the file.

- A new Finder window will pop up. From the package delete the project.xcworkspace file. Don’t worry. It’s another package.

- Go into the xcuserdata folder and delete your own .xcuserdatad folder.

- Close Finder and open Xcode. Clean and rebuild your app.

Xcode 4 build gcc-4.2 error, execvp: No such file or directory error

Mike D. — Wed, 22 Jun 2011 02:02:07 +0000

Question: After downgrading from Xcode 4.2 beta to Xcode SDK 4.02 I am facing new error messages:

- “gcc-4.2: error trying to exec ‘/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/arm-apple-darwin10-gcc-4.2.1′: execvp: No such file or directory”, and

– “Command /Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/gcc-4.2 failed with exit code 255″.

What’s is this for and what to do now?

Answer: Check out your build configuration. The Architectures probably have an inherited $(ARCHS_…) value which can fire a build error:

1. Navigate to Build Settings in Xcode and check out values in the Architectures group.

2. Remove “VALID ARCH” entry from Architectures field to reset settings. Use $(ARCHS_STANDARD_32_BIT) , or armv6, armv7 values as you wish. $(ARCHS_STANDARD_32_BIT) should show armv6 armv7.

3. Repeat these steps at your dependent projects.