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

Corel Painter 20.1.0.285 - Digital art s...
Corel Painter lets you advance your digital art style with painted textures, subtle glazing brushwork, interactive gradients, and realistic Natural-Media. Easily transition from traditional to... Read more
iTubeDownloader 6.5.19 - Easily download...
iTubeDownloader is a powerful-yet-simple YouTube downloader for the masses. Because it contains a proprietary browser, you can browse YouTube like you normally would. When you see something you want... Read more
OmniFocus 3.8 - GTD task manager with iO...
OmniFocus is an organizer app. It uses projects to organize tasks naturally, and then add tags to organize across projects. Easily enter tasks when you’re on the go, and process them when you have... Read more
Hazel 4.4.5 - Create rules for organizin...
Hazel is your personal housekeeper, organizing and cleaning folders based on rules you define. Hazel can also manage your trash and uninstall your applications. Organize your files using a familiar... Read more
Macs Fan Control 1.5.7 - Monitor and con...
Macs Fan Control allows you to monitor and control almost any aspect of your computer's fans, with support for controlling fan speed, temperature sensors pane, menu-bar icon, and autostart with... Read more
Acorn 6.6 - Bitmap image editor.
Acorn is a new image editor built with one goal in mind - simplicity. Fast, easy, and fluid, Acorn provides the options you'll need without any overhead. Acorn feels right, and won't drain your bank... Read more
OnyX 3.8.2 - Maintenance and optimizatio...
OnyX is a multifunction utility that you can use to verify the startup disk and the structure of its system files, to run miscellaneous maintenance and cleaning tasks, to configure parameters in the... Read more
macOS Catalina 10.15.5 - An Operating Sy...
macOS Catalina gives you more of everything you love about Mac. Experience three all-new media apps: Apple Music, Apple TV, and Apple Podcasts. Locate a missing Mac with the new Find My app. And now... Read more
macOS High Sierra Security Updates 10.13...
macOS High Sierra introduces new core technologies that improve the most important functions of your Mac. From rearchitecting how it stores your data to improving the efficiency of video streaming to... Read more
Numi 3.28 - Menu-bar calculator supports...
Numi is a calculator that magically combines calculations with text, and allows you to freely share your computations. Numi combines text editor and calculator Support plain English. For example, '5... Read more

Latest Forum Discussions

See All

Steam Link Spotlight - Signs of the Sojo...
Steam Link Spotlight is a feature where we look at PC games that play exceptionally well using the Steam Link app. Our last entry was XCOM: Chimera Squad. Read about how it plays using Steam Link's new mouse and keyboard support over here. | Read more »
Steampunk Tower 2, DreamGate's sequ...
Steampunk Tower 2 is a DreamGate's follow up to their previous tower defence game. It's available now for both iOS and Android as a free-to-play title and will see players defending their lone base by kitting it out with a variety of turrets. [... | Read more »
Clash Royale: The Road to Legendary Aren...
Supercell recently celebrated its 10th anniversary and their best title, Clash Royale, is as good as it's ever been. Even for lapsed players, returning to the game is as easy as can be. If you want to join us in picking the game back up, we've put... | Read more »
Pokemon Go Fest 2020 will be a virtual e...
Niantic has announced that Pokemon Go Fest will still take place this year although understandably it won't be a physical event. Instead, it will become a virtual celebration and is set to be held on 25th and 26th July. [Read more] | Read more »
Marvel Future Fight's major May upd...
Marvel Future Fight's latest update has now landed, and it sounds like a big one. The focus this time around is on Marvel's Guardians of the Galaxy, and it introduces all-new characters, quests, and uniforms for players to collect. [Read more] | Read more »
SINoALICE, Yoko Taro and Pokelabo's...
Yoko Taro and developer Pokelabo's SINoALICE has now opened for pre-registration over on the App Store. It's already amassed 1.5 million Android pre-registrations, and it's currently slated to launch on July 1st. [Read more] | Read more »
Masketeers: Idle Has Fallen's lates...
Masketeers: Idle Has Fallen is the latest endeavour from Appxplore, the folks behind Crab War, Thor: War of Tapnarok and Light A Way. It's an idle RPG that's currently available for Android in Early Access and will head to iOS at a later date. [... | Read more »
Evil Hunter Tycoon celebrates 2 million...
Evil Hunter Tycoon has proved to be quite the hit since launching back in March, with its most recent milestone being 2 million downloads. To celebrate the achievement, developer Super Planet has released a new updated called Darkness' Front Yard... | Read more »
Peak's Edge is an intriguing roguel...
Peak's Edge is an upcoming roguelike puzzle game from developer Kenny Sun that's heading for both iOS and Android on June 4th as a free-to-play title. It will see players rolling a pyramid shape through a variety of different levels. [Read more] | Read more »
Clash Royale: The Road to Legendary Aren...
Supercell recently celebrated its 10th anniversary and their best title, Clash Royale, is as good as it's ever been. Even for lapsed players, returning to the game is as easy as can be. If you want to join us in picking the game back up, we've put... | Read more »

Price Scanner via MacPrices.net

New 16″ MacBook Pros now on sale for up to $2...
Apple reseller DataVision is now offering new 16″ Apple MacBook Pros for up to $255 off MSRP, each including free shipping. Prices start at $2194. DataVision charges sales tax for NY, NJ, PA, and CA... Read more
Apple now offering Certified Refurbished iPho...
Apple is now offering Certified Refurbished iPhone Xr models in the refurbished section of their online store starting at $499. Each iPhone comes with Apple’s standard one-year warranty, ships free,... Read more
Sale! Get a 10.2″ 32GB WiFi iPad for only $27...
Walmart has new 10.2″ 32GB WiFi iPads on sale for $50 off Apple’s MSRP, only $279. These are the same iPads sold by Apple in their retail and online stores. Be sure to select Walmart as the seller... Read more
Apple resellers offer new 2020 Mac minis for...
Apple resellers are offering new 2020 Mac minis for up to $50 off Apple’s MSRP with prices available starting at $759. Shipping is free: (1) B&H Photo: – 2020 4-Core Mac mini: $759 $40 off MSRP... Read more
Sprint is offering the Apple iPhone 11 free t...
Did you miss out on Sprint’s recent free iPhone SE promotion? No worries. Sprint has the 64GB iPhone 11 available for $0 per month for new lines when you trade-in a qualifying phone in any condition... Read more
Apple has clearance 2019 13″ 1.4GHz MacBook P...
Apple has Certified Refurbished 2019 13″ 1.4GHz 4-Core Touch Bar MacBook Pros available today starting at $979 and up to $440 off original MSRP. Apple’s one-year warranty is included, shipping is... Read more
Apple restocks 2019 MacBook Airs starting at...
Apple has clearance, Certified Refurbished, 2019 13″ MacBook Airs available again starting at $779. Each MacBook features a new outer case, comes with a standard Apple one-year warranty, and is... Read more
Apple restocks clearance Mac minis for only $...
Apple has restocked Certified Refurbished 2018 4-Core Mac minis for only $599. Each mini comes with a new outer case plus a standard Apple one-year warranty. Shipping is free: – 3.6GHz Quad-Core... Read more
Apple’s new 2020 13″ MacBook Airs on sale for...
B&H Photo has Apple’s new 2020 13″ 4-Core and 6-Core MacBook Airs on sale today for $50-$100 off Apple’s MSRP, starting at $949. Expedited shipping is free to many addresses in the US. The... Read more
B&H continues to offer clearance 2019 13″...
B&H Photo has clearance 2019 13″ 4-Core MacBook Pros available for up to $300 off Apple’s original MSRP, with prices starting at $1149. Expedited shipping is free to many addresses in the US. B... Read more

Jobs Board

Security Officer - *Apple* Store - NANA (Un...
**Security Officer \- Apple Store** **Description** About NMS Built on a culture of safety and integrity, NMSdelivers award\-winning, integrated support services to Read more
Transition Into Practice Program (TIP) - Sept...
…Academy-Transition into Practice (TIP) Residency program at St Mary Medical Center in Apple Valley, CA. **We are seekingRegistered Nurses who are:** + New graduate Read more
Essbase Developer - *Apple* - Theorem, LLC...
Job Summary Apple is seeking an experienced, detail-minded Essbase developer to join our worldwide business development and strategy team. If you are someone who Read more
Senior Software Engineer @ *Apple* - Theore...
Job Summary Apple is looking for a seasoned senior software engineer to join our worldwide business development and strategy team. This is an opportunity to lead a Read more
Cub Foods - *Apple* Valley - Now Hiring Par...
Cub Foods - Apple Valley - Now Hiring Part Time! United States of America, Minnesota, Apple Valley Retail Operations Post Date May 18, 2020 Requisition # 119230 Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.