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

Minecraft 1.19.3 - Popular sandbox build...
Minecraft allows players to build constructions out of textured cubes in a 3D procedurally generated world. Other activities in the game include exploration, gathering resources, crafting, and combat... Read more
Boom 3D 1.4.0 - $19.99
Boom 3D is a revolutionary app with 3D Surround Sound and phenomenally rich and intense audio that is realistic and works on any headphones. Features 3D surround sound Built-in audio player... Read more
Visual Studio Code 1.74.0 - Cross-platfo...
Visual Studio Code provides developers with a new choice of developer tool that combines the simplicity and streamlined experience of a code editor with the best of what developers need for their... Read more
Notion 2.1.9 - A unified workspace for m...
Notion is the unified workspace for modern teams. Features: Integration with Slack Documents Wikis Tasks More guests: invite up to 10 collaborators, friends & family to your pages Page... Read more
Spotify 1.2.0.1165 - Stream music, creat...
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
Thunderbird 102.5.1 - Email client from...
As of July 2012, Thunderbird has transitioned to a new governance model, with new features being developed by the broader free software and open source community, and security fixes and improvements... Read more
Pinegrow 7.03 - Mockup and design web pa...
Pinegrow (was Pinegrow Web Designer) is desktop app that lets you mockup and design webpages faster with multi-page editing, CSS and LESS styling, and smart components for Bootstrap, Foundation,... Read more
Adobe After Effects 2022 23.1 - Create p...
The new, more connected Adobe After Effects can make the impossible possible. Get powerful new features like a Live 3D Pipeline that brings CINEMA 4D scenes in as layers - without intermediate... Read more
SteerMouse 5.6.7 - Powerful third-party...
SteerMouse is an advanced driver for USB and Bluetooth mice. SteerMouse can assign various functions to buttons that Apple's software does not allow, including double-clicks, modifier clicks,... Read more
Wireshark 4.0.2 - Network protocol analy...
Wireshark is one of the world's foremost network protocol analyzers, and is the standard in many parts of the industry. It is the continuation of a project that started in 1998. Hundreds of... Read more

Latest Forum Discussions

See All

Level Infinite announce December events...
The hit MMORPG Tower of Fantasy will receive a new update in December, along with a powerful new Simulacrum. Players will be able to explore new areas of Mirroria with fun new games and take part in a big new event. [Read more] | Read more »
Dead Cells: Return to Castlevania DLC Re...
Dead Cells on iOS from Playdigious recently released on Apple Arcade in the form of Dead Cells+ (). Dead Cells+ is an App Store Great featuring all prior DLC and updates. At The Game Awards 2022, Motion Twin revealed the next major DLC for Dead... | Read more »
‘Among Us’ Hide and Seek Mode Update Com...
At The Game Awards 2022, Innersloth announced the next major update for Among Us (Free). This update is arriving today for all platforms and it will bring in the new Hide n Seek game mode alongside new cosmetics and pets. This update is the game’s... | Read more »
Massively Popular ‘Vampire Survivors’ Is...
Ahead of The Game Awards 2022, the massively popular Vampire Survivors (Free) has released on iOS and Android for free. Vampire Survivors is one of the most popular PC games right now, and it is a regular on every Steam Deck most-played list from... | Read more »
SwitchArcade Round-Up: ‘Chained Echoes’,...
Hello gentle readers, and welcome to the SwitchArcade Round-Up for December 8th, 2022. Today is Thursday, and that usually means an absolute deluge of new releases on the eShop. But the year is winding down, so we’ve only got ten or so to look at... | Read more »
‘Awaken Legends: Idle RPG’ Celebrates th...
Awaken Legends: Idle RPG is adding its first update since the game was soft-launched in November, letting players get their hands on a new hero “Hera Valen". Players can also look forward to the Covenant of the Dark Knight event and the Wishing Well... | Read more »
‘Horizon Chase 2’ Japan World Tour Expan...
Horizon Chase 2 () from Aquiris is getting a major expansion today on Apple Arcade. The Japan World Tour expansion brings in 11 new races across 9 cities and it should be rolling out now as of this writing. I expect it to be available worldwide... | Read more »
Dark Fantasy Visual Novel ‘The 13th Mont...
Originally announced for release in August, The 13th Month from Japanese developer Kobayashimaru and publisher Kodansha released on PC via Steam worldwide this month. The dark fantasy visual novel that reimagines the classic Sleeping Beauty tale, is... | Read more »
Tom Clancey’s The Divison Resurgence ann...
Ubisoft has announced the latest Live Test dates for Tom Clancy’s The Division Resurgence, the hotly anticipated mobile entry in the Divison series. Starting December 8th and ending on the 22nd, the test will offer a huge amount of content for the... | Read more »
‘Easy Come Easy Golf’ New Update Adds St...
Easy Come Easy Golf () from Clap Hanz is one of my favorite games on Apple Arcade. It has been updated quite a bit since launch bringing in new modes and improvements. It recently launched on Nintendo Switch as well. | Read more »

Price Scanner via MacPrices.net

Lowest price of the season: 2022 Apple AirPod...
Verizon has new 2022 AirPods Pro in stock and on sale for $199.99 shipped as part of their Holiday sale. Their price is $50 off Apple’s MSRP, and it’s the lowest price currently available for 2022... Read more
New! Details on Verizon’s Christmas/Holiday p...
Verizon is offering discounts on iPhones, Apple Watch models, and iPads with specific promo codes as part of their Christmas/Holiday 2022 offerings. Codes are valid when adding a new line of service... Read more
Apple MagSafe accessories are back on Holiday...
Amazon has Apple MagSafe Chargers and Apple’s MagSafe Battery on sale for up to 24% off MSRP again as part of their Christmas/Holiday sale. Shipping is free, and all models are in stock: – MagSafe... Read more
13″ M2 MacBook Airs on sale again for the low...
Amazon has 13″ MacBook Airs with M2 CPUs in stock today and on sale for $150 off MSRP as part of their Christmas/Holiday Sale, prices start at $1049. Shipping is free. They are the lowest prices... Read more
Get an Apple 16″ MacBook Pro for $400 off MSR...
16″ MacBook Pros with Apple’s M1 Pro CPUs are in stock and on sale today at B&H Photo for $300-$400 off Apple’s MSRP for a limited time. Prices start at $2099 for M1 Pro models with 512GB or 1TB... Read more
Holiday clearance sale! Previous-generation A...
Amazon has 2nd generation 32GB and 64GB 4K Apple TVs with Siri remotes and 32GB Apple TV HDs on clearance sale for $80-$90 off original MSRP. Shipping is free, and delivery is available in time for... Read more
Christmas sale at Verizon: Apple AirPods Pro...
Verizon has first-generation Apple AirPods Pro on sale for $159.99 on their online store as part of their continuing Christmas/Holiday sale. Their price is $90 off Apple’s original MSRP, and it’s the... Read more
New Christmas/New Years promo at Xfinity Mobi...
Switch to Xfinity Mobile and open a new line of service, and take $400 off the price of a new iPhone, no trade-in required, through January 10, 2023. The $400 is applied to your account as credits... Read more
Apple iPad Smart Keyboard Folio prices drop u...
Apple iPad Smart Keyboard Folio prices have dropped up to $60 off MSRP at Amazon and Walmart as part of their Christmas/Holiday sales. These are the cheapest prices currently available for these iPad... Read more
Today is the final day for Xfinity Mobile’s $...
If you switch to Xfinity Mobile and open a new line of service, they will take $500 off the price of a new iPhone, no trade-in required. This is the best no trade-in Cyber Monday Apple iPhone 14 deal... Read more

Jobs Board

*Apple* Systems Administrator - JAMF - Activ...
…Administration **Duties and Responsibilities** + Configure and maintain the client's Apple Device Management (ADM) solution. The current solution is JAMF supporting Read more
Cashier - *Apple* Blossom Mall - JCPenney (...
Cashier - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Blossom Mall Read more
Omnichannel Associate - *Apple* Blossom Mal...
Omnichannel Associate - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Read more
Sephora Beauty Advisor - *Apple* Blossom Ma...
Sephora Beauty Advisor - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Read more
Operations Associate - *Apple* Blossom Mall...
Operations Associate - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.