TweetFollow Us on Twitter

Obj Support Lib Version History

Volume Number: 13 (1997)
Issue Number: 7
Column Tag: develop

Object Support Library Version History

by Andy Bachorski, Apple Developer Technical Support (DTS) devsupport@apple.com

This article is an attempt to clarify the version history of Apple's Object Support Library (OSL). This library provides routines that applications can use to support the Open Scripting Architecture (OSA) object model.

OSL was originally released as a 68K static library. With the introduction of Power Macintosh systems, OSL was repackaged as a shared library. When the Code Fragment Manager 68K Runtime Enabler (CFM-68K) was released, it became a fat library containing both Power PC and CFM-68K versions of OSL.

This article lists all versions of OSL that are currently available along with a brief history and description of each one, and recommendations as to which versions to use (and not use).

If you develop Macintosh applications that provide OSA object model support, or need to use applications that do, you should read this article.

In the Beginning of OSL

When the OSL was first released, it was a 68K static library (AEObjectSupportLib.o) that was statically linked into applications that supported the OSA object model. This is still the case for classic 68K applications.

With the release of the Power Macintosh and the accompanying CFM shared library application model, it was decide that a shared library version of the OSL (ObjectSupportLib), rather than a '.o' file, should be provided for PowerPC-native applications. This would allow native applications to take advantage of the shared library application model.

The OSL PowerPC shared library was released as version 1.0.2. It was included with the first Power Macintosh system software (version 7.1.2) and the AppleScript SDK version 1.1. It is currently still available on the Mac OS SDK CDs. This version of the OSL has a number of known bugs in its handling of whose clauses. (These bugs are listed in the Known Bugs in the OSL section of this Article.)

This first shared library introduced the first OSL shared library problem. The OSL was written in Pascal, but there were no PowerPC Pascal compilers, so it contained a small PowerPC-native library that loaded a 68K code resource containing the OSL.

But this loading was not done properly; the ObjectSupportLib's resource file often ended up in the middle of an application's resource chain. This problem was worked around in system 7.5.2 by forcing the Finder to load the OSL when it started up, thus forcing OSL's resource file to be located in the system, where it did no harm. This work-around masked the problem for all system versions after 7.5.2, but the problem is still there for earlier system versions.

After the introduction of the Power Macintosh, work began to convert the OSL source code from Pascal to C. This conversion was needed in order to provide a shared library containing both PowerPC and CFM-68K code. The converted fat OSL was released as version 1.0.4, which was included on the E.T.O. CD-ROM releases until recently.

There were a number of problems, however, with this version of the OSL, the worst of which was that a Gestalt selector installed by version 1.0.2 was not being installed by version 1.0.4. This prevented applications that were testing for this Gestalt selector from detecting the presence of the OSL shared library.

Note: A Gestalt selector is not the best method for detecting the presence of the OSL, but this decision was made early in the development of the code fragment model and the liabilities of using Gestalt were not yet well understood. The preferred method would have been to have developers compare a symbol in the library to kUnresolvedCFragSymbolAddress. (For details of this process, see Technote 1083: Weak-Linking to a Code Fragment Manager-based

Shared Library)

The other major problem with this version of the OSL was a number of bugs in the code that handled whose clause resolution (in addition to those previously mentioned). These bugs would cause an application to return incorrect results and/or error messages when they were presented with valid requests. Because of the missing Gestalt selector which prevented this version's use, the whose clause resolution bugs were not discovered until much later.

No Code Changes, Just Version Changes

Somewhere between versions 1.0.2 and 1.0.4, a mistake was made in the build process for the AppleScript 1.1 SDK which led to version 1.0.2 of the OSL being released as version 1.1. There is no difference in the actual code, only a new version number.

This meant we now had a 1.1 version which is really older than version 1.0.4. But installers complain when you try to install v1.0.4 over 1.1 because they think you are replacing a newer version with an older one. So when Apple shipped the Apple Telecom software version of OSL, 1.0.4 was changed to 1.1.1. This allowed the installer to replace the old version with the new. Again, no code changes, just a version change. (All the old problems, of course, were still there).

This is the point where many people started having problems; we now had a situation where a (generally) well-behaved version 1.1 was being replaced with a broken version 1.1.1.

A Valiant Attempt To Fix Things

The AppleScript team, at this point, decided that enough was enough--it was time to move forward and fix things. They released a version that fixed the Gestalt selector problem and called it 1.1.1. But no one had told them about the Apple Telecom OSL version 1.1.1, so they changed the version to 1.1.2. But, again, someone else had already made a limited release of an OSL version 1.1.2.

This was unfortunate, but not a major problem--they just incremented the version to 1.1.3. This version, which contained the fixed Gestalt selector, got a limited developer release. Great--now the applications which couldn't load it before due to the Gestalt selector bug could use the OSL. But when these applications loaded the OSL, they revealed all sorts of interesting behaviors resulting from the OSL's inability to resolve whose clauses. (Remember that no one had actually executed this code before the Gestalt bug was fixed.)

Back to the Drawing Board

The AppleScript team started looking at the 1.0.4/1.1.1 code stream in more detail and, after considering what a fix might mean to the stability of existing applications, it was decided that the risk of further trouble was too great. The decision was made to return to the older 1.0.2/1.1 code stream for the next release of the OSL.

As a result, the resource-loading source stream in version 1.0.2 was revised so it could be compiled as a native PowerPC and CFM-68K library. The resource-loading bug was also addressed. This revised library was tested, sent to a small group of developers for further testing, and then approved for final build as version 1.1.4.

Along the way, though, there was a new wrinkle added to this story. In order to fit in with the Mac OS reference release strategy, the file's creator type got changed, along with with its version number, which changed to 1.1.6.

Note: Version 1.1.4 appears on the Developer CD Series and the Mac OS SDK CD, while version 1.1.6 appears on certain E.T.O. CDs.

But we still have more to our story. It seems that the test suite used to validate the OSL tested for the presence of the Gestalt selector, but did not determine if it was properly installed. Basically, native OSL resource-loading code wasn't doing the right thing when it installed its Gestalt selector, which could lead to crashes in certain situations.

In the meantime, Version 1.1.6 was included as part of the Harmony (Mac OS 7.6) f3 build that was seeded to developers. When this latest OSL problem was discovered, the decision was made to take the version 1.0.2 of OSL and reversion it (again) as version 1.1.8. This is the version of OSL that is included in the GM version of Mac OS 7.6.

The biggest problem with this version is that it isn't fat, as it doesn't contains CFM-68K code (recall that 1.0.2 didn't, either). This wasn't an immediate problem, since Mac OS 7.6 shipped without support for CFM-68K. In fact, 7.6 explicitly checks for the presence of the current CFM-68K extension and disables it to prevent its loading with this version of the system. If you can't run CFM-68K, you don't need a fat OSL.

A New Hope

Thanks to the efforts of a number of engineers, the OSL got a more thorough rewrite which fixed both the Gestalt selector and resource file bugs. The testing was completed and the problems were resolved. This time, the OSL was released as version 1.2, which now generally works as expected. It still contains the bugs related to whose clause resolution, but they are not fatal and are easy for developers to work around (see Known Bugs in the OSL).

The World As We Know It

With all this said and done, you're probably scratching your head and

wondering, "What version should I be using, anyway?" At this time (April, 1997) the answer to that question is (drum roll, please):

You should be using version 1.2 of the Object Support Library.

If you don't have access to this version, then use 1.1.8 (or one of its twins, versions 1.0.2 or 1.1). Keep in mind that these older versions are not fat, which means that they won't work with CFM-68K applications. If you need to run a CFM-68K application, you must use version 1.2.

And, of course, you should install newer version of the OSL as they are released.

The History of OSL

1.0.2
First PowerPC shared library, resource file bug
1.0.4
New code base, no Gestalt selector, other bugs
1.1
Really just 1.0.2 in disguise, new creator code
1.1.1
1.0.4's twin (warts and all)
1.1.2/1.1.3
Never publicly released, so don't look for it
1.1.4
Doesn't work, but released on OS SDK CD
1.1.6
Version that shipped with Harmony f3
1.1.8
Version that shipped with Mac OS 7.6 (another 1.0.2 clone)
1.2
Shipped with CFM-68K 4.0; fixes all known crashing bugs

Known Bugs in the OSL

There are still several known bugs in the OSL, but they all have workarounds.

Unlocked Handles Passed To Compare Functions

You can install an object comparison function for use when resolving whose clauses. When the OSL calls your comparison function, it passes pointers to two AEDescs: one for the object being compared, and one for the object or descriptor to compare to the first.

The problem here is that the memory blocks containing the descriptor records pointed to by the parameters are located in relocatable blocks that are not locked and may move after the compare function is called.

The workaround for this problem is to copy the descriptor records pointed to by the parameters to a local variable as soon as you enter the object comparison routine.

There is a complication to this problem involving Classic 68K applications and the segment loader. If the comparison function and the AEObjectSupportLib.o library are not in the same segment when you build your application, it's possible for the descriptor records to move before they are copied if the segment containing the OSL is not already loaded.

The workaround for this problem is to make sure that the comparison function and the AEObjectSupportLib.o library are in the same segment when you build your application.

Memory Leak in Object Comparison Callback Function During whose Clause Resolution

There is a memory leak when the OSL calls an application-supplied comparison callback function while resolving whose clauses in object specifiers. When the OSL passes objects to the comparison callback function, those objects will often be application-defined tokens that are created by object accessor functions.

The problem is that the OSL calls AEDisposeDesc on these token objects rather than AEDisposeToken, which causes a memory leak--any data the application has attached to the token is not properly disposed of.

This problem is further complicated by the unlocked handles bug described above. The workaround is to combine the unlocked handles fix with disposing the tokens yourself. The pseudo-code below describes the work-around for this problem and also the unlocked handle problem above:

Pascal version

function MyCompareObjects( comparisonOperator:  DescType;
                  (CONST) VAR theObject:      AEDesc;
                  (CONST) VAR objOrDescToCompare:  AEDesc;
                  VAR compareResult:      boolean): OSErr;
var
  theObjectCopy              : AEDesc;
  objOrDescToCompareCopy     : AEDesc;
begin
  { First make copies of the descriptors because the OSL has them pointing
   into a relocatable block, which can be moved by the code below. }
        theObjectCopy := theObject;
        objOrDescToCompareCopy := objOrDescToCompare;
  { Now set the original desciptors to the null descriptor since we have
   to dispose of the objects below because of this OSL bug! }
  SetToNullDesc( theObject );
  SetToNullDesc( objOrDescToCompare );
  { Code to do the comparison goes here }
  MyCompareObjects := DoTheComparison( comparisonOperator, theObjectCopy,
                     objOrDescToCompareCopy, compareResult );
  { These descriptors are supposed to be const, but the OSL never calls
   our dispose token callback function, so we dispose of them here in
   case one of them is an application-defined token. }
  MyDisposeToken( theObjectCopy );
  MyDisposeToken( objOrDescToCompareCopy );
end;

C version
OSErr MyCompareObjects( DescType    comparisonOperator,
            const AEDesc  *theObject,
            const AEDesc  *objOrDescToCompare,
            Boolean     *compareResult )
{
  AEDesc theObjectCopy;
  AEDesc objOrDescToCompareCopy;
  OSErr  anErr;
  theObjectCopy = theObject;
  objOrDescToCompareCopy = objOrDescToCompare;
  SetToNullDesc( theObject );
  SetToNullDesc( objOrDescToCompare );
  anErr = DoTheComparison( comparisonOperator, theObjectCopy,
               objOrDescToCompareCopy, compareResult );
  MyDisposeToken( theObjectCopy );
  MyDisposeToken( objOrDescToCompareCopy );
}

Memory Leak in marking Callback Functions During whose Clause Resolution

There is a memory leak when the OSL calls application-provided marking functions during the processing of whose clauses in object specifiers.

In the process of resolving an object specifier, a descriptor record is created and passed to the mark token callback function (as the containerToken parameter) and object-marking callback function (as the theToken parameter). The problem is that the OSL never disposes of this descriptor, either through AEDisposeToken or AEDisposeDesc.

The problem can be avoided by having your application resolve all whose clauses it receives on its own. This way it can avoid calling AEResolve. This can be advantageous, especially for the most common types of object specifiers. However, you can potentially receive "uncommon" object specifiers that are better handled by the OSL using your callback functions; if you handled them yourself you'd end up duplicating most of the OSL.

Fortunately, the workaround for this problem is relatively simple: dispose of the descriptor record at the end of the object-marking function and set it to a null descriptor. This fix should not cause problems if this bug is fixed in a future release of the OSL, since it's always safe to dispose of a null descriptor record.

Function to set descriptor record to null descriptor

void SetToNullDesc( AEDesc theObject ) { theObject.descriptorType = typeNull; theObject.dataHandle = nil; }

Further Reference

Technote 1083: Weak-Linking to a Code Fragment Manager-based Shared Library

Acknowledgments

Special thanks to Chris Espinosa, Roger Pantos, Bryn Oh, and Otto Schlosser.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Audio Hijack 3.2.0 - Record and enhance...
Audio Hijack (was Audio Hijack Pro) drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio... Read more
FontExplorer X Pro 5.0.1 - Font manageme...
FontExplorer X Pro is optimized for professional use; it's the solution that gives you the power you need to manage all your fonts. Now you can more easily manage, activate and organize your... Read more
Calcbot 1.0.2 - Intelligent calculator a...
Calcbot is an intelligent calculator and unit converter for the rest of us. Featuring an easy-to-read history tape, expression view, intuitive conversion, and much more! Features History Tape -... Read more
MTR 5.0.0.1 - The Mac's oldest and...
MTR (was MacTheRipper)--the Mac's oldest and smartest DVD-backup app--is now updated to version 5.001 MTR -- the complete toolbox, not a one-trick, point-and-click extractor. MTR is intended for... Read more
LibreOffice 4.4.5.2 - Free, open-source...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
Adobe Lightroom 6.1.1 - Import, develop,...
Adobe Lightroom is available as part of Adobe Creative Cloud for as little as $9.99/month bundled with Photoshop CC as part of the photography package. Lightroom 6 is also available for purchase as a... Read more
File Juicer 4.41 - Extract images, video...
File Juicer is a drag-and-drop can opener and data archaeologist. Its specialty is to find and extract images, video, audio, or text from files which are hard to open in other ways. It finds and... Read more
A Better Finder Rename 9.52 - File, phot...
A Better Finder Rename is the most complete renaming solution available on the market today. That's why, since 1996, tens of thousands of hobbyists, professionals and businesses depend on A Better... Read more
OmniFocus 2.2.3 - GTD task manager with...
OmniFocus helps you manage your tasks the way that you want, freeing you to focus your attention on the things that matter to you most. Capturing tasks and ideas is always a keyboard shortcut away in... Read more
TinkerTool 5.4 - Expanded preference set...
TinkerTool is an application that gives you access to additional preference settings Apple has built into Mac OS X. This allows to activate hidden features in the operating system and in some of the... Read more

Cosmonautica (Games)
Cosmonautica 1.1 Device: iOS Universal Category: Games Price: $6.99, Version: 1.1 (iTunes) Description: Cast off! Are you ready for some hilarious adventures in outer space? | Read more »
Rescue humanity from a Demon horde in An...
Angel Stone is Fincon's follow up to the massively successful Hello Hero and is out now on iOS and Android. You play as a member of The Resistance, a group of mighty human warriors who have risen up in defiance of the Demon horde threatening to... | Read more »
Gallery Doctor (Photography)
Gallery Doctor 1.0 Device: iOS iPhone Category: Photography Price: $2.99, Version: 1.0 (iTunes) Description: Free up valuable iCloud and iPhone storage with Gallery Doctor, the only iPhone cleaner that automatically identifies the... | Read more »
You Against Me (Games)
You Against Me 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: A simple game… You. Me. Claim, steal, lock, score, win! | Read more »
Yep, it's True - Angry Birds 2 is O...
The not exactly rumors were true and the birds are back. Angry Birds 2 has come to the App Store and the world will... well I suppose it'll still be the same, but now we have more bird-flinging options! [Read more] | Read more »
You Could Design Your Own Card for Chain...
If you've ever wanted to create your own item, weapon, trap, or even monster for Chainsaw Warrior: Lords of the Night, this is your chance. Auroch Digital is currently holding a contest so that fans can fight to the death (not really) to see which... | Read more »
Bitcoin Billionaire is Going Back in Tim...
If you thought you managed to buy everything there is to buy in Bitcoin Billionaire and make all the money, well you though wrong. Those of you who made it far enough might remember investing in time travel - and it looks like that investment is... | Read more »
Domino Drop (Games)
Domino Drop 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Domino Drop is a delightful new puzzle game with dominos and gravity!Learn how to play it in a minute, master it day by day.Your... | Read more »
OPERATION DRACULA (Games)
OPERATION DRACULA 1.0.1 Device: iOS Universal Category: Games Price: $5.99, Version: 1.0.1 (iTunes) Description: 25% off launch sale!!! 'Could prove to be one of the most accurate representations of the Japanese bullet hell shmup... | Read more »
Race The Sun (Games)
Race The Sun 1.01 Device: iOS iPhone Category: Games Price: $4.99, Version: 1.01 (iTunes) Description: You are a solar craft. The sun is your death timer. Hurtle towards the sunset at breakneck speed in a futile race against time.... | Read more »

Price Scanner via MacPrices.net

Sale! 13-inch MacBook Pros on sale for $100 o...
B&H Photo has 13″ MacBook Pros on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.5GHz/500GB MacBook Pro: $999.99 save $100 - 13″ 2.7GHz/128GB Retina... Read more
Sale! Save $100 on 13-inch MacBook Airs this...
B&H Photo has the 13″ 1.6GHz/128GB MacBook Air on sale for $899.99 including free shipping plus NY tax only. Their price is $100 off MSRP, and it’s the lowest price available for this model.... Read more
Worldwide Tablet Market Decline Continues, Ap...
The worldwide tablet market declined -7.0% year-over-year in the second quarter of 2015 (2Q15) with shipments totaling 44.7 million units according to preliminary data from the International Data... Read more
TP-LINK TL-PA8030P KIT Powerline Featuring Ho...
Consumer and business networking products provider TP-LINK is now shipping its TL-PA8030P KIT AV1200 3-Port Gigabit Passthrough Powerline Starter Kit that expands your home’s network over its... Read more
Apple refurbished iPad Air 2s available for u...
The Apple Store has Apple Certified Refurbished iPad Air 2s available for up to $140 off the price of new models. Apple’s one-year warranty is included with each model, and shipping is free: - 128GB... Read more
Updated Apple iPad Price Trackers
We’ve updated our iPad Air Price Tracker and our iPad mini Price Tracker with the latest information on prices and availability from Apple and other resellers. Read more
Apple refurbished 2014 13-inch 128GB MacBook...
The Apple Store has Apple Certified Refurbished 2014 13″ MacBook Airs available starting at $759. An Apple one-year warranty is included with each MacBook, and shipping is free: - 13″ 1.4GHz/128GB... Read more
Apple’s Education discount saves up to $300 o...
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
Save up to $600 with Apple refurbished Mac Pr...
The Apple Store has Apple Certified Refurbished Mac Pros available for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. 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

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales. Specialist - Retail Customer Service and Sales. Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Online Store UAT Lead - Apple (Unite...
**Job Summary** The Apple Online Store is a fast paced and ever evolving business environment. The User Acceptance Testing (UAT) lead in this organization is able to Read more
*Apple* MAC Support Services Subject Matter...
Title: Apple MAC Support Services Subject Matter Expert Location: Pleasanton, CA Type of position: Temporary Contract for approximately 6 weeks Tasks The tasks for the Read more
Lead Infrastructure Engineer - *Apple* /Mac P...
…of a team * Requires proven problem solving skills Preferred Additional: * Apple Certified System Administrator (ACSA) * Apple Certified Technical Coordinator (ACTC) Read more
*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.