TweetFollow Us on Twitter

March 94 - KON & BAL'S PUZZLE PAGE

KON & BAL'S PUZZLE PAGE

WHEN MAPS GO BAD

KONSTANTIN OTHMER AND BRUCE LEAK

[IMAGE 130-134_Puzzle_Page_rev1.GIF]

See if you can solve this programming puzzle, presented in the form of a dialogbetween Konstantin Othmer (KON) and Bruce Leak (BAL). The dialog gives cluesto help you. Keep guessing until you're done; your score is the number to the left ofthe clue that gave you the correct answer. These problems are supposed to be tough. If you don't get a high score, at least you'll learn interesting Macintosh trivia.

KON: I have a Macintosh IIfx at home with a 13-inch color monitor and an old Kong.

BAL You mean the black-and-white two-page display? That thing is out of production. Programmers were the only ones who bought it, and we already sold one to every Macintosh programmer. I've got one too.

KON Mine's probably older, though. Fung gave me one of the prototype units that were blocking the entrance to his office about five years ago.

BAL Does it have the stylish metal cheese grater cage around it or did you actually get a plastic case?

KON I scored one with plastic, though it's yellow now from sitting in the sun. Anyway, now that the PowerPC workload is finally winding down, I've actually spent some time at home. I started playing around with Darryl's mapping program on my fx.

BAL MacAtlas?

KON Yeah. It's pretty cool. The problem is I can't open files.

BAL Command-O open? What happens?

KON Nothing. No Standard File, no dancing bears -- it's as if I never gave the Open command.

BAL I've never had a problem with that program. Does the menu get highlighted?

KON Yeah. Every once in a while you'll see it flash. This problem happens systemwide; I can't even open files in ResEdit.

BAL Can you drag documents onto the application icon in the Finder to open them?

KON Yeah. Everything not related to Standard File seems to work fine. I can edit files, play movies -- even file sharing works.

BAL What version of the system are you running? Does printing work?

100 KON I'm running System 7.1. I can't save and then print as recommended by our print shop because there's a problem with Standard File, but other than that it works fine. Why?

BAL This one's easy, KON. Something is locked down in your MultiFinder heap, so your system heap can't grow. Standard File can't bring in all its resources, so it punts. Are you running that skanky StockItToMe server that Timo and Rubinowitz wrote?

90 KON This happens just after boot and I've got mounds of RAM now that I've removed DAL. I do a heap dump (hd) of the MultiFinder heap and there are no locked blocks at the bottom, so the system heap can grow all it wants. Furthermore, the heap total (ht) command shows that there's plenty of room in the system heap.

BAL Clearly this bug is limited to your home machine. I figure you have some slimy KON code on there that's only half debugged -- maybe a beta version of WonderPrint. Set an ATB on Standard File, 'PACK' 3, and then try to open a document.

80 KON I hit the A-trap, but when I trace over it it just returns without putting up the Standard File dialog.

BAL Is the package getting loaded?

70 KON Yeah.

BAL Since I don't have the source to Standard File handy, I'll use the log command and then the conditional step command to get a trace of all the instructions executed inside the package. I figure it should be fairly easy to spot some error condition where the code decides to bail. Since the _Pack3 instruction is two bytes, if the call to it is at the current PC address, I use the MacsBug commands

log MyStdFileLog
s pc=pc+2

to step, logging each instruction to a file and then stopping as soon as the trap is exited.

60 KON Wow, that conditional stepping is pretty cool. I didn't know MacsBug was that sophisticated. You could have just put a breakpoint on the other side of the _Pack3 and stepped a zillion instructions. Anyway, the trace isn't prohibitively long. Standard File preloads all the resources it needs to display the dialog, checking each one to see if it was loaded properly. When it tries to load LDEF -4000, it fails and bails.

BAL All the resources it needs must come from the System file. Check to see if LDEF - 4000 exists in the system.

55 KON According to ResEdit, the LDEF isn't present in the System file.

BAL Compare the LDEFs in your system with a fresh installation.

50 KON The LDEFs are all the same except one, which has a different resource ID.

BAL Well, it sounds like you've got a trashed System file. Copy and paste the bad LDEF into your system and reboot.

45 KON Everything works fine now, but if I drag-install a new system, Standard File fails. Fixing the LDEF is addressing the symptom, not the problem.

BAL You drag the good System file over and reboot, and Standard File is broken again?

KON Yep.

BAL Check the LDEF with ResEdit.

40 KON It's renumbered again.

BAL So something is trashing the resource map during boot. What if I boot with the Shift key held down to disable extension loading?

35 KON According to ResEdit, the resource map is still trashed.

BAL Try dumping resources of type 'LDEF' with the command rd LDEF at interesting times during the boot process.

30 KON If you hold down the Control key to enter MacsBug just after it's installed, the LDEF resources are fine. If you check it again when you're in the Finder, the LDEF is bad.

BAL So I use

atb hopenresfile ';dm @(sp+2);rd LDEF;g 

to watch extensions load during the boot process. The command breaks as each
extension is loaded and displays the name of the extension and the current state of all
LDEF resources. When I see the LDEF go bad, I've gone a long way toward finding
the offending code.

KON During the 7.1 boot process, the system patches are loaded from disk and installed.
One of those patches opens all the font files in that crazy font folder. After all the
patches are installed, the system extensions
are loaded, starting with the 8*24 GC card. It's loaded first so that QuickDraw is in a
well-defined state before other system extensions go and patch out the world; once
third parties start getting in there, it's a free-for-all.

BAL Obviously, all the system patches need to be installed before extensions are loaded so
that the extensions can take advantage of improvements provided by the patches.
Haven't you ever wondered why booting takes so long?

25 KON While the font files are being opened, the resource map is fine. But just before the
first extension is loaded, the resource map is bad.

BAL We need to narrow down where the map is going bad. I'll look through the system
map for the ID that's getting stepped on. First I get the size of the resource map
handle by using

wh @@sysmaphndl 

Then I can find the resource ID with

f @@sysmaphndl size f060

since F060 is hex for -4000, the resource ID that's getting smashed.

20 KON Good try, but you find seven occurrences.

BAL So I continue until the map goes bad, and check for -4000 again. I'll find the one that's changed, reboot, and step-spy on that address. Ta-da!

15 KON Sorry, but the resource map is a handle and it has moved on you. You can identify the one that's changed, but you can't step-spy on it since it's moving around all the time.

BAL Fine. I'll reboot in 24-bit mode, lock the handle down by setting the high bit of the resource map handle's master pointer, and step-spy on the address. Over.

10 KON Now Standard File works fine, but file sharing is starting to act flaky.

BAL OK. So I'm going to have to brute force it. I'll break when the last font loads. I'll log the MacsBug output to a file with log myLDEFFile and then atb ';rd LDEF;g to break on all traps and dump all the LDEF resources. I'll also do anatc hopenresfile and then an atb hopenresfile to clear the rd LDEF;g when HOpenResFile is hit. This way we'll fall into MacsBug when the first INIT is opened. Then I'll let it rip and get some lunch.

5 KON Pretty snazzy there, BAL. Before the map goes bad you see a bunch of Slot Manager calls and control calls. The last trap that gets called before the map goes bad is a control call to the driver which seems to originate from within InitGDevice.

BAL Hmmm. We're at secondary INIT time. The driver gets called again since all the system patches are now loaded. We added this because monitors boot back to the same configuration they were in when the machine was shut down. With 32-Bit QuickDraw, the machine could have been shut down in 32-bit video mode, so the driver needs to be called a second time after the system patches (where 32-Bit QuickDraw lives) are loaded.

KON Yeah, the call that's killing the map is a call to the driver to set the bit depth. At secondary INIT time the 'scrn' resource is read to find out what the last bit depth was, and each device is called to set the depth up properly.

BAL The call must be going to the bogus Kong video card Fung gave you. What's the ROM version on that thing?

KON It's a beta ROM. When I asked Mike Puckett about it he said there was some nasty "fungus" in the code, and that it was fixed before final. He gave me a new video ROM, and now everything works great. Real-world users would never experience this, of course, since the problem was corrected long before the card went out.

BAL You and Van Brink should share packrat stories. You never know, some of that old equipment might become collector's items some day.

KON This problem began when I started using MacAtlas because I switched my Kong into grayscale mode. My system is a lot more stable now that those spurious writes have been fixed. Before I tracked this bug down, I was having intermittent problems.

BAL Nasty.

KON Yeah.

KONSTANTIN OTHMER AND BRUCE LEAK regularly change their AppleLink addresses through various front companies to help defray their tax losses from dealings in the stock market. They're currently trying to corner the market on masked ROMs, particularly 680x0 ROMs targeted at PowerPC processor-based machines. They were last seen looking for a '57 Corvette in good condition and are willing to swap debugging services in trade. *

SCORING

  • 80-100 This is a special category reserved for Waldemar and Jasik.
  • 50-70 Weekends spent at Weird Stuff Warehouse or Van Brink's garage are starting to pay off.
  • 25-45 You're spending too much time playing with that 3DO interactive multiplayer machine at your local electronics store.
  • 5-20 You're spending too much time at the gym. *

Thanks to Peter Hoddie, Brian McGhie, and Mike Puckett for reviewing this column. *

 
AAPL
$100.58
Apple Inc.
+0.01
MSFT
$45.22
Microsoft Corpora
+0.27
GOOG
$583.37
Google Inc.
-1.12

MacTech Search:
Community Search:

Software Updates via MacUpdate

Pages 5.2.2 - Apple's word processo...
Apple Pages is a powerful word processor that gives you everything you need to create documents that look beautiful. And read beautifully. It lets you work seamlessly between Mac and iOS devices. And... Read more
Quicken 2015 2.0.1 - Complete personal f...
The new Quicken 2015 helps you manage all your personal finances in one place, so you can see where you're spending and where you can save. Quicken automatically categorizes your financial... Read more
CleanMyMac 2.2.7 - Delete files that was...
CleanMyMac makes space for the things you love. Sporting a range of ingenious new features, CleanMyMac 2 lets you safely and intelligently scan and clean your entire system, delete large, unused... Read more
MacFamilyTree 7.2.4 - Create and explore...
MacFamilyTree gives genealogy a facelift: it's modern, interactive, incredibly fast, and easy to use. We're convinced that generations of chroniclers would have loved to trade in their genealogy... Read more
Videobox 4.1.1 - Download Flash video th...
Videobox allows you to quickly and easily download Flash video from most all of the popular video sites on the internet. Videobox will convert the video into a native Quicktime format so it's ready... Read more
Web Snapper 3.3.5 - Capture entire Web p...
Web Snapper lets you capture Web pages exactly as they appear in your browser. You can send them to a file as images or vector-based, multi-page PDFs. It captures the whole Web page - eliminating... Read more
Picasa 3.9.138 - Organize, edit, and sha...
Picasa and Picasa Web Albums allows you to organize, edit, and upload your photos to the Web from your computer in quick, simple steps. Arrange your photos into folders and albums and erase their... Read more
Tidy Up 3.0.15.0 - Find duplicate files...
Tidy Up is a complete duplicate finder and disk-tidiness utility. With Tidy Up you can search for duplicate files and packages by the owner application, content, type, creator, extension, time... Read more
Parallels Desktop 10.0 - Run Windows app...
Parallels Desktop is simply the world's bestselling, top-rated, and most trusted solution for running Windows applications on your Mac. With Parallels Desktop for Mac, you can seamlessly run both... Read more
Apple Final Cut Pro X 10.1.3 - Professio...
Apple Final Cut Pro X is a professional video editing solution.Completely redesigned from the ground up, Final Cut Pro adds extraordinary speed, quality, and flexibility to every part of the post-... Read more

Latest Forum Discussions

See All

DotEmu Summer Sale Cuts Several Games’ P...
DotEmu Summer Sale Cuts Several Games’ Prices to $0.99 Posted by Ellis Spice on August 21st, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
King Announces its Newest “Saga” – Diamo...
King Announces its Newest “Saga” – Diamond Digger Saga Posted by Jessica Fisher on August 21st, 2014 [ permalink ] Diamond Digger Saga, by King Digital Entertainment, promises to be another addictive, adorable game in the “Saga” | Read more »
Spacetime Studios’ Greg Mueller Tells Al...
| Read more »
TourStar Review
TourStar Review By Rob Thomas on August 21st, 2014 Our Rating: :: BORING TOURINGUniversal App - Designed for iPhone and iPad When The Ramones sang “Touring, touring/It’s never boring,” they clearly weren’t referring to TourStar.... | Read more »
Track Your Pregnancy with Glow Nurture
Track Your Pregnancy with Glow Nurture Posted by Jessica Fisher on August 21st, 2014 [ permalink ] iPhone App - Designed for the iPhone, compatible with the iPad | Read more »
Outcast Odyssey – An Interview with the...
At this year’s San Diego Comic-Con, fans got the chance to meet and mingle with several of the artists behind Magic Pixel Games and Namco Bandai’s upcoming card battler, Outcast Odyssey. Considering many of these artists have worked on comics in the... | Read more »
BoxPop Review
BoxPop Review By Jennifer Allen on August 21st, 2014 Our Rating: :: UNTAXING PUZZLESUniversal App - Designed for iPhone and iPad Move from tile to tile to clear the board in this slightly too simple and easy puzzle game.   | Read more »
Breakdown Buddy Review
Breakdown Buddy Review By Jennifer Allen on August 21st, 2014 Our Rating: :: FLAWED CONCEPTiPhone App - Designed for the iPhone, compatible with the iPad There’s a good idea here, but Breakdown Buddy isn’t as useful as it tries to... | Read more »
jamstik, the Guitar You Can Take Everywh...
jamstik, the Guitar You Can Take Everywhere, is Now Available for Purchase Posted by Jessica Fisher on August 21st, 2014 [ permalink ] Zivix has announced that their guitar-in-your-pocket, | Read more »
Star Walk 2 - Guide to the Sky Day and N...
Star Walk 2 - Guide to the Sky Day and Night 1.0.0 Device: iOS Universal Category: Education Price: $2.99, Version: 1.0.0 (iTunes) Description: The next generation of the best-selling Star Walk, winner of Apple Design Award, used by... | Read more »

Price Scanner via MacPrices.net

21-inch iMacs on sale for up to $150 off MSRP
B&H Photo has 21″ iMacs on sale for up to $150 off MSRP including free shipping plus NY sales tax only. B&H will also include a free copy of Parallels Desktop software: - 21″ 2.7GHz iMac: $... Read more
27-inch 3.2GHz iMac on sale for $1698, save $...
Abt has the 27″ 3.2GHz iMac on sale for $1698 including free shipping. Their price is $101 off MSRP. Read more
Mac Backup Guru 2.0 Drive Backup/Cloneing Uti...
Mac Backup Guru developer MacDaddy has released Mac Backup Guru 2.0, offering new and enhanced advanced features, such as bootable backups, synchronised volumes and folders, and a Snapshot mode that... Read more
Operate GE’s New Free-Standing KItchen Range...
Think you accidentally left the oven on? Switch it off while on the go. The new free-standing Profile™ Series gas and electric ranges are GE’s second cooking appliances, following their wall oven, to... Read more
Parallels Announces Parallels Desktop 10 for...
The no. 1-selling software for running Windows applications on a Mac becomes an even easier choice for millions of consumers and IT professionals worldwide with the launch of the most powerful... Read more
Apple now offering certified refurbished 2014...
 The Apple Store is now offering Apple Certified Refurbished 2014 MacBook Airs for up to $180 off the cost of new models. An Apple one-year warranty is included with each MacBook, and shipping is... Read more
Best Buy’s College Student Deals: $100 off Ma...
Take an additional $100 off all MacBooks and iMacs, $50 off iPad Airs and iPad minis, at Best Buy Online with their College Students Deals Savings, valid through September 6th. Anyone with a valid .... Read more
MacBook Airs on sale for $100 off MSRP, free...
B&H Photo has three 2014 MacBook Airs on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only. They also include free copies of Parallels Desktop and LoJack for Laptops... Read more
Razer Taipan Mouse For Gamers And Non-Gamers...
If you’re a serious gamer on either Mac or Windows PCs, a serious gaming mouse is a necessity for first-tier performance. However, even if like me you’re not much of a gamer, there’s still a strong... Read more
15-inch 2.2GHz MacBook Pro on sale for $1899,...
Adorama has the new 15″ 2.2GHz Retina MacBook Pro on sale for $1899 including free shipping plus NY & NJ sales tax only. Their price is $100 off MSRP, and it’s the lowest price available for this... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Position Opening at *Apple* - Apple (United...
**Job Summary** As more and more people discover Apple , they visit our stores seeking ways to incorporate our products into their lives. It's your job, as a Store Read more
Position Opening at *Apple* - Apple (United...
…Summary** As a Specialist, you help create the energy and excitement around Apple products, providing the right solutions and getting products into customers' hands. You Read more
Project Manager, *Apple* Financial Services...
**Job Summary** Apple Financial Services (AFS) offers consumers, businesses and educational institutions ways to finance Apple purchases. We work with national and Read more
*Apple* Solutions Consultant (ASC)- Retail S...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.