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. *

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

jAlbum Pro 12.6.4 - Organize your digita...
jAlbum Pro has all the features you love in jAlbum, but comes with a commercial license. With jAlbum, you can create gorgeous custom photo galleries for the Web without writing a line of code!... Read more
jAlbum 12.6.4 - Create custom photo gall...
With jAlbum, you can create gorgeous custom photo galleries for the Web without writing a line of code! Beginner-friendly, with pro results Simply drag and drop photos into groups, choose a design... Read more
Microsoft Remote Desktop 8.0.16 - Connec...
With Microsoft Remote Desktop, you can connect to a remote PC and your work resources from almost anywhere. Experience the power of Windows with RemoteFX in a Remote Desktop client designed to help... Read more
Spotify 1.0.4.90. - Stream music, create...
Spotify is a streaming music service that gives you on-demand access to millions of songs. Whether you like driving rock, silky R&B, or grandiose classical music, Spotify's massive catalogue puts... Read more
djay Pro 1.1 - Transform your Mac into a...
djay Pro provides a complete toolkit for performing DJs. Its unique modern interface is built around a sophisticated integration with iTunes and Spotify, giving you instant access to millions of... Read more
Vivaldi 1.0.118.19 - Lightweight browser...
Vivaldi browser. In 1994, two programmers started working on a web browser. Our idea was to make a really fast browser, capable of running on limited hardware, keeping in mind that users are... Read more
Stacks 2.6.11 - New way to create pages...
Stacks is a new way to create pages in RapidWeaver. It's a plugin designed to combine drag-and-drop simplicity with the power of fluid layout. Features: Fluid Layout: Stacks lets you build pages... Read more
xScope 4.1.3 - Onscreen graphic measurem...
xScope is powerful set of tools that are ideal for measuring, inspecting, and testing on-screen graphics and layouts. Its tools float above your desktop windows and can be accessed via a toolbar,... Read more
Cyberduck 4.7 - FTP and SFTP browser. (F...
Cyberduck is a robust FTP/FTP-TLS/SFTP browser for the Mac whose lack of visual clutter and cleverly intuitive features make it easy to use. Support for external editors and system technologies such... Read more
Labels & Addresses 1.7 - Powerful la...
Labels & Addresses is a home and office tool for printing all sorts of labels, envelopes, inventory labels, and price tags. Merge-printing capability makes the program a great tool for holiday... Read more

This Week at 148Apps: April 20-24, 2015
The Apps of April How do you know what apps are worth your time and money? Just look to the review team at 148Apps. We sort through the chaos and find the apps you're looking for. The ones we love become Editor’s Choice, standing out above the many... | Read more »
Discover Your Reflexes With Minimalist G...
Discover O, BYOF Studios, may look simple at first with its' color matching premise and swipe controls, but as you speed up the task becomes more daunting. [Read more] | Read more »
Here's Another Roundup of Notable A...
Now that the Apple Watch is publically available (kind of), even more apps and games have been popping up for it. Some of them are updates to existing software, others are brand new. The main thing is that they're all for the Apple Watch, and if you... | Read more »
Use Batting Average and the Apple Watch...
Batting Average, by Pixolini, is designed to help you manage your statistics. Every time you go to bat, you can use your Apple Watch to track  your swings, strikes, and hits. [Read more] | Read more »
Celebrate Studio Pango's 3rd Annive...
It is time to party, Pangoland pals! Studio Pango is celebrating their 3rd birthday and their gift to you is a new update to Pangoland. [Read more] | Read more »
Become the World's Most Important D...
Must Deliver, by cherrypick games, is a top-down endless-runner witha healthy dose of the living dead. [Read more] | Read more »
SoundHound + LiveLyrics is Making its De...
SoundHound Inc. has announced that SoundHound + LiveLyrics, will be one of the first third-party apps to hit the Apple Watch. With  SoundHound you'll be able to tap on your watch and have the app recognize the music you are listening to, then have... | Read more »
Adobe Joins the Apple Watch Lineup With...
A whole tidal wave of apps are headed for the Apple Watch, and Adobe has joined in with 3 new ways to enhance your creativity and collaborate with others. The watch apps pair with iPad/iPhone apps to give you total control over your Adobe projects... | Read more »
Z Steel Soldiers, Sequel to Kavcom'...
Kavcom has released Z Steel Soldiers, which continues the story of the comedic RTS originally created by the Bitmap Brothers. [Read more] | Read more »
Seene Lets You Create 3D Images With You...
Seene, by Obvious Engineering, is a 3D capture app that's meant to allow you to create visually stunning 3D images with a tap of your finger, and then share them as a 3D photo, video or gif. [Read more] | Read more »

Price Scanner via MacPrices.net

Final day for Best Buy’s 4 Day Sale: Up to $3...
Best Buy has the new 2015 13″ 1.6GHz/128GB MacBook Air on sale for $799.99 through April 27th. That’s $200 off MSRP, and it’s the lowest price available for this new model from any reseller. Choose... Read more
College Student Deals: Additional $50 off Mac...
Take an additional $50 off all MacBooks and iMacs at Best Buy Online with their College Students Deals Savings, valid through May 9, 2015. Anyone with a valid .EDU email address can take advantage of... Read more
Save up to $300 on a new Mac, $30 on an iPad,...
Purchase a new Mac or iPad at The Apple Store for Education and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free,... Read more
Zoho Business Apps for Apple Watch Put Select...
Pleasanton, California based Zoho has launched Zoho Business Apps for Apple Watch, a line of apps that extends Zoho business applications to let users perform select functions from an Apple Watch.... Read more
Universal Stylus Initiative Launched to Creat...
OEMs, stylus and touch controller manufacturers have announced the launch of Universal Stylus Initiative (USI), a new organization formed to develop and promote an industry specification for an... Read more
Amazon Shopping App for Apple Watch
With the new Amazon shopping app for Apple Watch, Amazon customers with one of the wearable devices can simply tap the app on the watch to purchase items in seconds, or save an idea for later. The... Read more
Mac Pros on sale for up to $260 off MSRP
B&H Photo has Mac Pros on sale for up to $260 off MSRP. Shipping is free, and B&H charges sales tax in NY only: - 3.7GHz 4-core Mac Pro: $2799, $200 off MSRP - 3.5GHz 6-core Mac Pro: $3719.99... Read more
Apple refurbished Time Capsules available for...
The Apple Store has certified refurbished Time Capsules available for $100 off MSRP. Apple’s one-year warranty is included with each Time Capsule, and shipping is free: - 2TB Time Capsule: $199, $100... Read more
Intel Compute Stick: A New Mini-Computing For...
The Intel Compute Stick, a new pocket-sized computer based on a quad-core Intel Atom processor running Windows 8.1 with Bing, is available now through Intel Authorized Dealers across much of the... Read more
Heal to Launch First One-Touch House Call Doc...
Santa Monica, California based Heal, a pioneer in on-demand personal health care services — will offer the first one-touch, on-demand house call doctor app for the Apple Watch. Heal’s Watch app,... Read more

Jobs Board

*Apple* iOS Specialist - TCML (United States...
AppleiOS Specialist Senior Apple /iOS Administrator/Engineer responsible for configuration and distribution of desktop, laptop and mobile devices to State Employees Read more
*Apple* Client Systems Solution Specialist -...
…drive revenue and profit in assigned sales segment and/or region specific to the Apple brand and product sets. This person will work directly with CDW Account Managers Read more
*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
*Apple* Support Technician IV - Jack Henry a...
Job Description Jack Henry & Associates is seeking an Apple Support Technician. This position while acting independently, ensures the proper day-to-day control of Read more
*Apple* Client Systems Solution Specialist -...
…drive revenue and profit in assigned sales segment and/or region specific to the Apple brand and product sets. This person will work directly with CDW Account Managers Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.