TweetFollow Us on Twitter

PowerPC Code
Volume Number:10
Issue Number:4
Column Tag:Powering Up

Connecting A 68k Object File
To PowerPC Code

A robust technique for loading and calling 68K modules from your PowerPC application

By Richard Clark, Apple Computer, Inc.

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

Many developers run into a major problem when porting code to PowerPC: incorporating 68K object models which came from an outside vendor. Since you can’t just hand a 68K module to the PowerPC linker, you have to find some alternative for loading the library and calling the library’s functions. Fortunately, developers can use the Code Fragment Manager and the Mixed Mode Manager together to solve this problem.

The solution involves creating a stand-alone version of the 68K code, then assembling a “jump table” of Universal Procedure Pointers which the application can use to call this code. Since applications (and, in fact, any PowerPC code fragment) can have global variables, it makes sense to allocate this table within the application. However, since the 68K library entry points are only available to the 68K code, that code has to create the universal procedure pointers. This would create an impossible dilemma except for one fact - both Mixed Mode and the Code Fragment Manager can be called from emulation on a Power Macintosh via A-Traps.

Thus we have a solution - the application must create the jump table as a global variable, and then pass its address to the 68K code which assembles the jump table. (An alternate method involves exporting the table from the application. The 68K code must open a connection back to the application, and ask the CFM for the address of the jump table.) The 68K code creates Universal Procedure Pointers to fill the table, which allows the application to call the library functions using Mixed Mode.

Creating the Jump Table

The first step is to prepare a list of all of the functions that your application calls in the library. Next, define ProcInfo values for each of these functions, using the MixedMode.h header and any header which defines callback functions (such as Controls.h) as a guide. You should also create macros for creating and calling a UniversalProcPtr in this way.

Next, create a data structure which contains Mixed Mode “Universal Procedure Pointers” for each of these functions. Put a copy of this data structure into a global variable in your PowerPC application, and don’t declare it as “static” (i.e. hidden.) You should also export this table, for a reason that will become clear shortly.

/* 1 */
// This is a header file common to the application and 68K code 

#include <ConditionalMacros.h>
#include <MixedMode.h>

typedef void (*CallbackPtr)(void); // A pointer which is fed to the library

typedef pascal OSErr (*Routine1ProcPtr)(CallbackPtr callbackRoutine);

enum {
 uppRoutine1ProcInfo = kPascalStackBased
  | RESULT_SIZE (SIZE_CODE(sizeof(OSErr)))
  | STACK_ROUTINE_PARAMETER(1, SIZE_CODE(sizeof(CallbackPtr)))

// Use these definitions if we're compiling for Power Macintosh or another
// Macintosh system which supports Mixed Mode
typedef UniversalProcPtr Routine1UPP;

#define CallRoutine1Proc(userRoutine, longValue)         \
 uppRoutine1ProcInfo, longValue)
#define NewRoutine1Proc(userRoutine) \
 (RoutineUPP) NewRoutineDescriptor((ProcPtr)userRoutine, \
    uppRoutine1ProcInfo, GetCurrentISA())
// Use these definitions if we're compiling for a 68K-based Macintosh
typedef Routine1ProcPtr Routine1UPP;

#define CallRoutine1Proc(userRoutine, longValue)         \
 (*((Routine1ProcPtr )userRoutine))(longValue)
#define NewRoutine1Proc(userRoutine) \

// Here's the list of Universal Procedure Pointers
struct JumpTable {

typedef struct JumpTable JumpTable, *JumpTablePtr;

// === Information on calling the 68K setup functions
typedef pascal OSErr (*SetupProcPtr)(JumpTablePtr);

enum {
 uppSetupProcInfo = kPascalStackBased
  | RESULT_SIZE (SIZE_CODE(sizeof(OSErr)))

// Use these definitions if we're compiling for Power Macintosh or another
// Macintosh system which supports Mixed Mode
typedef UniversalProcPtr SetupUPP;

#define CallSetupProc(userRoutine, jumpTableAddr)        \
 uppSetupProcInfo, jumpTableAddr)
#define NewSetupProc(userRoutine)  \
 (SetupUPP) NewRoutineDescriptor((ProcPtr)userRoutine, \
    uppSetupProcInfo, GetCurrentISA())
// Use these definitions if we're compiling for a 68K-based Macintosh
typedef SetupProcPtr SetupUPP;

#define CallSetupProc(userRoutine, jumpTableAddr)        \
#define NewSetupProc(userRoutine)  \

Next, you have to create the “setup” function in 68K code and link it to your 68K object library. This routine needs to fill in each of the pointers in the table. The resulting code should be compiled, linked, and made into a stand-alone 68K code resource.

Granted, this technique could prove difficult if the library depends on having an A5 world. If your 68K library requires global variables, you must apply one of the special coding techniques documented in the Macintosh Developer Technical Notes or develop magazine.) Also note that if you want this code to run on a 68K machine, you should check for the presence of Mixed Mode and react appropriately.

/* 2 */
pascal OSErr BuildJumpTable(JumpTablePtr theJumpTable)
// Build a table of pointers to functions in our linked library
 OSErr  err;
 // Fill in the table with pointers to each library function
 theJumpTable->routine1 = NewMyRoutineProc(Routine1);
 err = MemError();
 return err;

The alternate approach involves exporting the jump table from the Application using the CFM, and letting the 68K code ask the CFM for the table’s address. Note the use of a STR# resource to store the application and table name strings - this avoids needing an A5 world just for the string constants. (Note that this code will not work on a machine which doesn’t have the Code Fragment Manager or Mixed Mode.)

/* 3 */
OSErr   err;
 JumpTablePtr  theJumpTable;
 ConnectionID  connID = 0;
 Ptr    mainAddr;
 Str255 errName, appName, tableName;
 SymClass symClass;
// Locate the application that called us
 GetIndString(&appName, 128, 1); // Assuming the name is in a STR#
 err = GetSharedLibrary(&appName, kPowerPCArch, 0, 
 &connID, &mainAddr, &errName);
 if (err) goto done;
 // Now, locate the shared table
 // (it's a pointer stored in a global variable)
 GetIndString(&tableName, 128, 2);// The table name is in the same STR#
 err = FindSymbol(connID, &tableName, 
 (Ptr*)&myTablePointer, &symClass);
 if (err) goto done;
// Insert the code to create UniversalProcPtrs here
 if (connID)
  return err;

To initialize this table, simply load the code resource from the application and call it via Mixed Mode. When the resource returns, the jump table will be full of Universal Procedure Pointers. Therefore, you should then modify your application to use Mixed Mode and the pointers in the table to call the library functions.

/* 4 */
// include the usual macros for creating a UniversalProcPtr for our callback 
JumpTable gJumpTable;
// Load the stand-alone code
Handle  theResource;
theResource= Get1IndResource('STUB', 1);
if (theResource) {
  HLock(theResource);// Lock it -- and NEVER unlock it
  // Call the entry point, no parameters
  CallSetupProc(*theResource, &gJumpTable);  
 // we know it's 68K, so we didn't
 // bother with creating a Routine Descriptor
  // Create a UniversalProcPtr for our callback routine
  CallbackUPP ourCallback;
  ourCallback = NewCallbackProc(MyCallbackRoutine);
  result = CallRoutine1Proc(gJumpTable.routine1,ourCallback );

Note that since the library function takes a callback pointer, we had to create a UniversalProcPtr and pass that instead of the address of the actual code. (If we hadn't done this, the machine would crash.) Since this causes memory to be allocated for a Routine Descriptor, we call DisposeRoutineDescriptor afterwards to release the memory.

That’s all there is to it! This is a robust technique which is now being used in several commercial applications - perhaps it will prove useful in yours.


Community Search:
MacTech Search:

Software Updates via MacUpdate

Apple GarageBand 10.1.3 - Complete recor...
The new GarageBand is a whole music creation studio right inside your Mac -- complete with keyboard, synths, orchestral and percussion instruments, presets for guitar and voice, an entirely... Read more
Apple Compressor 4.3 - Adds power and fl...
Compressor adds power and flexibility to Final Cut Pro X export. Customize output settings, work faster with distributed encoding, and tap into a comprehensive set of delivery features. Powerful... Read more
Xcode 8.1 - Integrated development envir...
Xcode includes everything developers need to create great applications for Mac, iPhone, iPad, and Apple Watch. Xcode provides developers a unified workflow for user interface design, coding, testing... Read more
Apple Numbers 4.0.5 - Apple's sprea...
With Apple Numbers, sophisticated spreadsheets are just the start. The whole sheet is your canvas. Just add dramatic interactive charts, tables, and images that paint a revealing picture of your data... Read more
Apple Keynote 7.0.5 - Apple's prese...
Easily create gorgeous presentations with the all-new Keynote, featuring powerful yet easy-to-use tools and dazzling effects that will make you a very hard act to follow. The Theme Chooser lets you... Read more
Apple iMovie 10.1.3 - Edit personal vide...
With an all-new design, Apple iMovie lets you enjoy your videos like never before. Browse your clips more easily, instantly share your favorite moments, and create beautiful HD movies and Hollywood-... Read more
Apple Motion 5.3 - Create and customize...
Apple Motion is designed for video editors, Motion 5 lets you customize Final Cut Pro titles, transitions, and effects. Or create your own dazzling animations in 2D or 3D space, with real-time... Read more
Apple Pages 6.0.5 - Apple's word pr...
Apple Pages is a powerful word processor that gives you everything you need to create documents that look beautiful. And read beautifully. It lets you work seamlessly between Mac and iOS devices, and... Read more
Paperless 2.3.7 - $49.95
Paperless is a digital documents manager. Remember when everyone talked about how we would soon be a paperless society? Now it seems like we use paper more than ever. Let's face it - we need and we... Read more
DEVONthink Pro 2.9.6 - Knowledge base, i...
DEVONthink Pro is your essential assistant for today's world, where almost everything is digital. From shopping receipts to important research papers, your life often fills your hard drive in the... Read more

Latest Forum Discussions

See All

The Lost Shield (Games)
The Lost Shield 1.0.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0.0 (iTunes) Description: The Lost shield is a brick break/adventure game. You play as a hero who must return a powerful but dangerous magic shield... | Read more »
The Forgotten Room (Games)
The Forgotten Room 1.0.1 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0.1 (iTunes) Description: Play as paranormal investigator John “Buster of Ghosts” Murr as he explores yet another mysteriously creepy house. This... | Read more »
5 Halloween mobile games for wimps
If you're anything like me, horror games are a great way to have nightly nightmares for the next decade or three. They're off limits, but perhaps you want to get in on the Halloween celebrations in some way. Fortunately not all Halloween themed... | Read more »
The 5 scariest mobile games
It's the most wonderful time of the year for people who enjoy scaring themselves silly with haunted houses, movies, video games, and what have you. Mobile might not be the first platform you'd turn to for quality scares, but rest assured there are... | Read more »
Lifeline: Flatline (Games)
Lifeline: Flatline 1.0.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.0 (iTunes) Description: The Lifeline series takes a terrifying turn in this interactive horror experience. Every decision you make could help... | Read more »
Game of Dice is now available on Faceboo...
After celebrating its anniversary in style with a brand new update, there’s even more excitement in store for Game of Dice has after just being launched on Facebook Gameroom. A relatively new platform, Facebook Gameroom has been designed for PC... | Read more »
4 addictive clicker games like Best Fien...
Clickers are passive games that take advantage of basic human psychology to suck you in, and they're totally unashamed of that. As long as you're aware that this game has been created to take hold of your brain and leave you perfectly content to... | Read more »
Smile Inc. Guide: How not to die on the...
As if Mondays weren't bad enough, at Smile Inc. you have to deal with giant killer donuts, massive hungry staplers, and blasting zones. It's not exactly a happy, thriving work environment. In fact, you'll be lucky to survive the nine to five.... | Read more »
Oh...Sir! The Insult Simulator (Games)
Oh...Sir! The Insult Simulator 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: | Read more »
WitchSpring2 (Games)
WitchSpring2 1.27 Device: iOS Universal Category: Games Price: $3.99, Version: 1.27 (iTunes) Description: This is the story of Luna, the Moonlight Witch as she sets out into the world. This is a sequel to Witch Spring. Witch Spring 2... | Read more »

Price Scanner via

Apple Unveils Redesigned MacBook Pro With Tou...
October 27, 2016 – Apple today introduced the thinnest and lightest MacBook Pro yet, along with a new interface innovation that replaces the traditional row of function keys with a Retina-quality... Read more
Apple Unveils New TV App for Apple TV, iPhone...
October 27, 2016 – Apple today introduced a new TV app, offering a unified experience for discovering and accessing TV shows and movies from multiple apps on Apple TV, iPhone and iPad. The TV app... Read more
Price drops on select refurbished 2015 13″ Re...
Apple dropped prices on select Certified Refurbished 2015 13″ Retina MacBook Pros by as much as $90. An Apple one-year warranty is included with each model, and shipping is free: - 13″ 2.7GHz/256GB... Read more
Apple reveals new next-generation 15″ and 13″...
Apple today revealed their next-generation 15″ and 13″ MacBook Pros. The new models are thinner and lighter than before with a new aluminum design featuring an enhanced keyboard with retina, multi-... Read more
Worldwide Smartphone Shipments Up 1.0% Year o...
According to preliminary results from the International Data Corporation (IDC) Worldwide Quarterly Mobile Phone Tracker, vendors shipped a total of 362.9 million smartphones worldwide in the third... Read more
TuneBand Arm Band For iPhone 7 and 7 Plus Rel...
Grantwood Technology has added the TuneBand for iPhone 7 and 7 Plus to its smartphone armband series. The TuneBand provides a lightweight and comfortable way to wear the iPhone while running,... Read more
1.4GHz Mac mini on sale for $449, save $50
Adorama has the 1.4GHz Mac mini on sale for $50 off MSRP including free shipping plus NY & NJ sales tax only: - 1.4GHz Mac mini (Apple sku# MGEM2LL/A): $449 $50 off MSRP To purchase a mini at... Read more
21-inch 1.6GHz iMac on sale for $999, save $1...
B&H has the 21″ 1.6GHz Apple iMac on sale for $999 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
Macs’ Superior Enterprise Deployment Cost Eco...
IBM’s debunking of conventional wisdom and popular mythology about the relative cost of using Apple Mac computers as opposed to PCs running Microsoft Windows at the sixth annual Jamf Nation User... Read more
12-inch WiFi Apple iPad Pros on sale for $50-...
B&H Photo has 12″ WiFi Apple iPad Pros on sale for $50-$70 off MSRP, each including free shipping. B&H charges sales tax in NY only: - 12″ Space Gray 32GB WiFi iPad Pro: $749 $50 off MSRP -... Read more

Jobs Board

*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Software Engineering Intern: UI Applications...
Job Summary Apple is currently seeking enthusiastic interns who can work full-time for a minimum of 12-weeks between Fall 2015 and Summer 2016. Our software Read more
Security Data Analyst - *Apple* Information...
…data sources need to be collected to allow Information Security to better protect Apple employees and customers from a wide range of threats.Act as the subject Read more
*Apple* Retail - Multiple Positions - Apple,...
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* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 52812872 Houston, Texas, United States Posted: Oct. 18, 2016 Weekly Hours: 40.00 **Job Summary** As an Apple Solutions Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.