Lap Cat Software Blog

I’m delighted to announce that I’ve been hired as Rogue Amoeba Employee 008. (Employee 007 is Longwell, Justin Longwell.) I’ll be working on Rogue Amoeba’s apps as a software engineer, as well as providing comic relief. Thanks to Alex, Paul, and Quentin for this once-in-a-lifetime opportunity. My coworkers at Rogue Amoeba Software, LLC include fellow bloggers Mike Ash and Guy English. Together we form perhaps the most talented group of Mac programmers outside of Apple. (Yes, I’m talking to you, Adobe and Microsoft.) Indeed, I haven’t seen such an array of stars in one place since the Ghostbusters music video.

I’ve joined Rogue Amoeba just in time to miss WWDC ‘08. In an earlier post, I mentioned that I left Marko Karppinen & Co. LLC just in time to miss WWDC ‘07. (I’ll make it there someday! ) The question is, what have I been doing in the meantime? Backpacking through Europe? Rotting in Gitmo? Running for President? No, I’ve been working on super-secret projects for Francis Technical Services, LLC. Although FTS is a little-known company, its software is well-known, at least inside Apple. For example, FTS is responsible for Radar, the Apple-internal Cocoa app that opens when employees click on the funny-looking rdar://problem/ URLs you often see. The number at the end of the URL corresponds to the problem ID of the bugs you file on the web with Apple Bug Reporter (also known as RadarWeb). It’s useful to have one of these URLs available when communicating with Apple engineers, because their managers forbid them from lifting a finger without a Radar problem number.

While at FTS, I did some bug analysis for Radar: that is, analysis of bugs in Radar’s source code, not analysis of bugs in Radar’s database, to which as a contractor I had extremely limited access. However, I mostly worked on other projects, such as Radar’s sibling app Sonar. Apple’s DTS uses Sonar to communicate with ADC members (such as me!). If you’ve ever seen sonr://request/ URLs — the Mighty Quinn provides one in an Apple Mailing List post — those open in Sonar. (By the way, I’ve read all of your emails to DTS. No, you haven’t been accepted to the iPhone Developer Program. Stop whining.) Another project that I worked on was Merlin, an app for Apple’s Human Resources department. I think that Steve Jobs is doing an outstanding job at Apple, so before I left I used Merlin to double his annual salary.

I’d like to thank Dave Francis, the owner and founder of Francis Tech, for the opportunity to work there. Despite appearances, I’m not really the type to hop from job to job. I’ve just been looking for Mr. Right, LLC, a company to fall in love with, marry, and have baby apps with. (As for any other support claims, sorry Billie Jean.) I can see myself growing old with Rogue Amoeba. (Easy to see when you’re already old?) Besides, someone has to stick around and keep an eye on mikeash, stop him from taking over the world.

Now without further ado, please take out your credit card and buy some of our fine software. As a special bonus for our Leopard customers, your purchase will be (code-)signed by your favorite Rogue Amoeba star.

Alas, poor Panther! I knew him, Horatio. You, Horatio, I don’t know so well, and you’re creeping me out. Why did you bring me to the cemetery?

The good news is that the first beta version of Vienna 2.3.0 is now available for download. Actually, it’s more of a zeta version, if you know what I mean. (You don’t.) The changes from 2.2.2 are listed in the release notes. The bad news is that Vienna 2.3 won’t run on Mac OS X Panther. Vienna 2.2.2 is the last release that supports Panther. That sucks, but if you’re still running 10.3.9, you probably don’t care much about the latest and greatest software anyway. Vienna 2.2.2 will continue to be available at Sourceforge.

Yeeha, Jester’s dead! I am dangerous, ice man.

I apologize for not posting this earlier. I’ve been extremely busy lately, and I had discussed the issue with someone who said that he or she (he) was going to post about it (but hasn’t).

The security alert is for FileVault users running Mac OS X 10.5.2. You thought that FileVault encrypted your personal data, right? Wrong! In Mac OS X 10.5.2, the location of the CFNetwork caches was moved from ~/Library/Caches, which is within your home directory and thus encrypted, to /private/var/folders, which is not within your home directory and thus not encrypted. This means that anyone with physical access to your hard drive could, for example, determine which URLs you’ve loaded, even if your computer is shut down.

Note that nothing about this change was mentioned in the Mac OS X 10.5.2 release notes.

For further reference on this issue, see the thread that began in the WebKit SDK mailing list and was moved by me to the Macintosh Network Programming mailing list. Thanks to Eric Long, who noticed the change in the first place, and Ron Hunsinger, who performed testing that I was too lazy to do. (In my defense, I haven’t yet migrated my FileVault account from Tiger to Leopard, so the issue doesn’t affect me directly.)

This post is dedicated to E. Gary Gygax, the second greatest corrupter of youth in history. It’s about D&D, that is, DWARF and dSYM. As of 2008-02-27, the STABS debugging symbols format has been deprecated by Apple. The default value for the DEBUG_INFORMATION_FORMAT build setting in Xcode projects had been stabs, but now it’s time to move on. (I’m talking to you, Justin Long.) Our other options are dwarf or dwarf-with-dsym. Also cake or death.

With STABS, you could build the release version of your app with debugging symbols, make a copy of the executable MyApp.app/Contents/MacOS/MyApp to keep, strip the executable for shipping, and then use the unstripped executable for symbolizing crash reports by giving a space-separated list of stack trace addresses to the command-line tool atos. Unfortunately, atos cannot currently serve this purpose with DWARF. Unlike STABS, DWARF does not include the debugging symbols in the executable itself but merely includes references to the intermediate object files, which do contain debugging symbols. You can usually find these .o files in a sub-directory of the build/MyApp.build directory. If you delete the object files after building with dwarf, you won’t be able to step through your app’s code. (With stabs, the object files are refuse.) You also won’t be able to step through the code if you strip debugging symbols from your app, even if you keep the object files, because the references to the object files will be gone from the executable.

To avoid losing the debugging symbols for your app after stripping, you want to use the option dwarf-with-dsym. The DWARF with dSYM option performs an additional step beyond ordinary DWARF: it creates a separate MyApp.app.dSYM file that contains all of the debugging symbols for your app. In fact, the DWARF with dSYM option allows you to step through your code regardless of whether the executable is stripped! This is possible because gdb will look for the .dSYM file in the same directory as your app. It doesn’t need to know the name or location of the object files. If you don’t strip debugging symbols, you can use either the .o files or the .dSYM file for debugging, but for the local debug build of your app there’s no point in using dSYM, since that would just prolong your build time. You have better things to do than wait for builds, such as writing comments on Slashdot.

The trouble with atos is that it does not reliably find debugging information in .dSYM files for stripped executables. Although Apple’s documentation (as of 2007-04-02) says, “If you’re using DWARF dSYM files, you must be using the version of atos included in Xcode 3 (Mac OS X version 10.5)”, Apple’s engineers say, “The underlying framework that atos uses doesn’t support loading symbol names from dSYM files in Leopard.” In my testing, however, there doesn’t seem to be a difference between Leopard and Tiger, at least not with Xcode 2.5 on Tiger. On both Leopard and Tiger, atos successfully loads symbol names from .dSYM files (I deleted the .o files) for unstripped executables. For stripped executables, in contrast, atos frequently fails to load the symbol names, or even gives inaccurate results.

The CrashReporter Technical Note suggests loading your app and its .dSYM in gdb to translate stack trace addresses from crash reports. That’s like having to start your car in order to read the odometer. (Oh wait, I have to do that, Nissan!) An alternative method is the command-line tool dwarfdump. It requires only the .dSYM file, not a copy of your app, and its --lookup option will do the same job as gdb without the overhead.

Please note that by breathing, blinking, or moving at all, even to command-w this page, you thereby register your agreement not to disclose or discuss this information anywhere with anyone at any time, no matter the duress, torture, or water-boarding you may undergo to extract it. This agreement holds despite the fact that the information is publicly available on the internet for every person in the world to read. Failure to uphold this agreement will result in multiple, painful cat scratches, in certain cases leading to cat scratch fever.

Now that the Pats have won the Super Bowl, Rudy has won the GOP nomination, and the Jedi have won the Clone Wars, all is right with the world (and the galaxy), so we can focus again on our lives, on our families, and most important, on Cocoa. If you’re a Cocoa developer, you are morally required to open System Preferences, Keyboard & Mouse, Keyboard Shortcuts and select All controls in Full keyboard access. This is not optional. If you do not comply, you will be driven out of the Continuum and forced to spend the rest of your pitiful mortal existence writing kernel extensions.

With the mandatory preference setting, you will observe the full Cocoa key view loop. Actually, it doesn’t have to be a loop: it could be a key view cul-de-sac. Anyway, Apple clearly wants developers to “leave the driving to us”, i.e.,

-[NSWindow setAutorecalculatesKeyViewLoop:YES]

because configuring and updating the key view loop can be a pita — like training a cat. The docs make it sound oh so easy, but that’s only because the docs don’t cover the complex or problematic cases. Suppose, for example, that you have a scroll view enclosing a view that contains multiple controls. You want the key view loop to follow a particular route both outside and inside the scroll view. How should you hook up the views in Interface Builder? (Or in code, when you’re working without a nib.)

I believe that the proper way to handle an NSScrollView in a key view loop is to ignore it. Walk by quickly without making eye contact. Whatever you do, don’t engage in conversation! Otherwise you’ll get invited to coffee or lunch. The reason you can ignore NSScrollView is that it never actually becomes the firstResponder of an NSWindow. The scroll view returns YES from acceptsFirstResponder if its documentView does, but if you then call -[NSWindow makeFirstResponder:] with the scroll view as argument, the window’s first responder will end up being not the scroll view itself but rather its document view.

This behavior is adequate if the document view is a single control such as an NSTableView or an NSTextView (though maddeningly, an NSTextView tends to interpret the tab key as, well, a tab). In the window nib, you can simply include the scroll view in the window’s key view loop, ignoring the document view, and when the window loads, the scroll view will automatically rearrange the key view loop to make its NSClipView the nextKeyView, followed by the document view and then the scroll view’s original nextKeyView. The scroll view and the clip view are superfluous in the key view loop, however, because only the document view becomes the first responder when tabbing through the window.

This behind-the-curtain key-view wizardry may seem impressive, but the scroll view is really deaf, dumb, and blind. It has no idea about any loop you’ve defined within the document view. There is no way to inform the scroll view of the beginning and end points of the ’sub-loop’. If you attempt to insert the scroll view containing your sub-loop into the window’s key view loop, it will turn into either a key view dead end within the scroll view or a key view overpass, depending on the configuration.

To avoid these problems, simply connect your views together in the key view loop as if the scroll view did not even exist. You know, like Mac OS X Tiger. (Of course the keyboard firmware update requires Quick Look and Time Machine!) Only the views that become first responder — as opposed to becomeFirstResponder — need to be hooked up. When a cat is lying on the trackpad, you will be thankful for setting the key view loops in your app, and so will your users. Cat-friendliness is in fact the most crucial consideration for designing both software and hardware.

I am saying that I will neither aspire to nor accept — I repeat, I will neither aspire to nor accept — the positions of President of the State Council and Commander in Chief. I will, on the other hand, host the Tonight Show if asked. Hasta la vista!

At the risk of provoking their ire and being branded a moron, I wish to dispute a claim that has been made several times by Rixstep about a supposed security vulnerability in Leopard’s NSDocumentController: Cocoa’s document controller overrides file system permissions without authentication. As far as I can tell, this claim is false.

I should note at the outset that I have nothing personal against Rixstep. Their syndicated feed has long been among my (numerous) favorites that I subscribe to in Vienna, as you can see by downloading the exported opml from my blog. I welcome legitimate criticism of Apple, and I have found Rixstep’s articles entertaining in the past, though of late they have become overly juvenile. As far as the whole ‘Cross-Platform Bait & Switch’ incident is concerned, I can’t comment on the legality of reproducing the quotations, because I’m not a lawyer, but I don’t think that Rixstep can be accused of misquoting or quoting out of context in this case.

Anyway, I’ve included the full text below of the email I sent to Rixstep a month ago. Retraction was perhaps too much to hope for, but I thought they would at least stop making the false claim after reading my email. They haven’t, which is why I’m now ‘going public’. (This should knock Britney off the front page.)

Hi. I read your article at <http://rixstep.com/2/1/20071227,00.shtml>, and it got me a little worried, so I did some testing. My results are that NSDocumentController in Leopard does not allow you to override Unix permissions. In fact, NSDocumentController in Leopard is more strict than the Unix permissions: it won’t allow you to save a writable document when you don’t have write permissions for the enclosing directory.

You are correct that saving a document always deletes the existing file and creates a new one with a different inode, and you are also correct that some of the user-visible NSDocumentController warning messages are misleading. However, if you don’t have write permissions for a directory, then NSDocumentController won’t let you delete or add a file, and even if you do have write permissions for the directory, NSDocumentController won’t let you delete someone else’s file or add a file with the same name if the sticky bit is set.

Thus, I believe that the ramifications for system administrators are negligible. With certain Unix permissions, it has always been possible to delete a file in a directory and replace it with a new file of the same name. Leopard has not changed that at all, so system administrators should take the same precautions against this scenario that they have always taken.

-Jeff

You don’t have to take my conclusions for granted, though. In a matter of minutes, you should be able to throw together a bare-bones document-based application suitable for testing the behavior yourself.

I have no desire to discourage criticism of Apple or Leopard. There are major problems in Leopard, and I don’t yet find it acceptable for use as my primary operating system. I just think that this spurious security issue obscures the real issue of whether the new Leopard NSDocumentController behavior is desirable.

P.S. If you really want to talk about a waste of precious disk space, /Applications/Mail.app/Contents/Resources is an astounding 277 MB on Leopard.

Some people are apparently under the impression that firewall rules are the be-all and end-all of Mac OS X security. Deny all from any to me in. Before you spend days composing the perfect ipfw ruleset, however, take a look at sysctl. (You could spend days looking at sysctl.) One of the biggest misconceptions about Mac OS X — a misconception encouraged by the System Preferences UI — is that the firewall is not enabled out of the box. Nonsense!

net.inet.ip.fw.enable: 1

Admittedly, it’s a fairly flammable firewall (allow ip from any to any), but it’s enabled. More important, the default sysctl settings do provide at least a modest level of protection. For example:

net.inet.icmp.timestamp: 0
net.inet.icmp.maskrepl: 0

These prevent your machine from responding to ping -M time and ping -M mask requests. What time is it? Where the party at?

By Mac OS X herein I shall mean Leopard and Tiger. (Panther is not yet abandonware, but at this point it merely receives Christmas cards.) When you ’start’ the firewall in System Preferences, Tiger adds a number of rules to ipfw. Leopard, on the other hand, includes a new Apple-designed firewall that mostly replaces ipfw. Though Leopard respects custom ipfw rulesets, it adds no rules to ipfw when you choose to block incoming connections. I don’t know much about how the Leopard firewall works; presumably it protects you somehow or other.

Leopard does still employ ipfw for “Stealth Mode”. If you turn that on, both Leopard and Tiger add the rule deny icmp from any to me in icmptypes 8. Curiously, Stealth mode prevents you from ‘pinging yourself’ in Leopard but not in Tiger. For fun (according to a rather loose definition of fun), try ping localhost. Somebody bring me a mirror! The difference in behavior is due to the Tiger-only rule allow ip from any to any via lo* that precedes all other rules.

Looking at the ipfw rules, you might think that Stealth Mode is overrated, like Notre Dame football and most wines over three dollars. If you want to learn its true value, you need to consult sysctl.

net.inet.tcp.blackhole: 2
net.inet.udp.blackhole: 1

With these settings, your computer mercilessly crushes attackers into singularities, as well as dropping their packets without response when sent to closed ports.

It would be nice if Bonjour wasn’t so talkative, broadcasting its greetings to your entire LAN. Bonjour also complains loudly when told to shut up by the firewall. On the other hand, you’re going to have to broadcast anyway for DHCP. Moreover, your LAN will see your internet traffic, especially on wireless.

Whoa, I suddenly realized after all these years that if you’re a grown man who lives in an attic, hangs out with high school students, has an ‘office’ in the bathroom, and is known for one syllable utterances, you’re not cool. You’re a loser.

Although it seems late in the game to be adding new features to Tiger, Mac OS X 10.4.11 includes not only the high-profile Safari 3 update but also a few other interesting little additions. For instance, when you uncompress a .tar.gz file in Finder it no longer leaves behind a useless .tar that you have to manually trash. Neat!

Of course, it wouldn’t be Finder without some annoyance. The trade-off for un-cluttering your Desktop is up-cluttering your console.log:

BOMArchiveHelper[454] opened /Users/jeff/Desktop/.BAHEm7Xn/my-directory.tar

I’m not sure why they didn’t use tar xzf, which is approximately a billion times faster. Baby steps…

It should come as no surprise that Vienna 2.2.1 was released on Sunday. I’ve been too busy the last two days chipping my car out of the ice to write a post here. Release notes are available for the lazy, though real coders read the commit logs.

Contrary to expectations, this is not really a Leopard compatibility release. I would say that Vienna is not yet Leopard ready. On the other hand, I would also say that Leopard is not yet itself ready. So there you have it.

I bear a heavy burden now, for with the ongoing Hollywood writers strike I am the lone remaining source of pablum in the world. Actually, I was on strike too, from the bagel shop. You know I can’t blog without bagels! However, the recent reconciliation of DLR and EVH inspired us to put aside our differences, and I thought the offer of SCO stock options and tickets to a Broadway show was more than fair. Thus, there will be a series finale to Working without a nib. Maybe they’ll even name a space shuttle after my cat.

Speaking of cats — as I am prone to do — there is a new cat on the Mac (though none on the mat). Apple finally released Mac OS X 10.5, code named “Leopard”, followed soon thereafter by Mac OS X 10.5.1, code named “Oops”. These updates to Mac OS X pose a problem for the Nibless project, because the crucial method +[NSObject poseAsClass:] has been deprecated in Leopard. In fact, this method does not work at all in the Leopard 64-bit runtime.

Fortunately, the new Leopard Objective-C runtime provides a nice solution to the problem. In earlier versions of Nibless we used poseAsClass: to override +[NSBundle loadNibNamed:owner:] while still allowing the original method to be called. We can accomplish the same thing in Leopard via a technique that computer scientists have termed the old switcheroo:

Class bundleClass = [NSBundle class];
Method originalMethod = class_getClassMethod(bundleClass, @selector(loadNibNamed:owner:));
Method categoryMethod = class_getClassMethod(bundleClass, @selector(JJ_loadNibNamed:owner:));
method_exchangeImplementations(originalMethod, categoryMethod);

These functions are documented in the Objective-C 2.0 Runtime Reference. It is straightforward to exchange the method implementations; the mind-bending trick is to call the original implementation afterward.

+(BOOL) JJ_loadNibNamed:(NSString *)aNibName owner:(id)owner
{
	BOOL didLoadNib = YES;
	if (aNibName != nil || owner != NSApp)
	{
		didLoadNib = [self JJ_loadNibNamed:aNibName owner:owner];
	}
	return didLoadNib;
}

Before the function method_exchangeImplementations() is called, the method JJ_loadNibNamed:owner: has the implementation defined above, but the method never gets called until that implementation has been given to the method loadNibNamed:owner:, at which point the method JJ_loadNibNamed:owner: has the original implementation of loadNibNamed:owner:, whatever that may be (only Apple and Uri Geller know for sure). We never get caught in an infinite loop, unlike poor Alice and Norman.

The Leopard version of Nibless you’ve long been waiting for — since the second paragraph — is ready for download. If you find it useful, then please send me a bagel. I’ll also accept a doughnut, but not a Danish. Spoon!