TweetFollow Us on Twitter

Dec 96 Factory Floor
Volume Number:12
Issue Number:12
Column Tag:From The Factory Floor

Marcel Achim, Pascal Reanimator

By Dave Mark, ©1996 by Metrowerks, Inc., all rights reserved.

This month’s Factory Floor interview is with Marcel Achim, the heart and soul of Metrowerks Pascal efforts. As Neil never tires of reminding me, Pascal is alive and well and, in one publisher’s opinion, still a wonderful language.

Dave: How did you hook up with Metrowerks?

Marcel: I was recruited on the university campus by the then VP of Research who was teaching there. I became involved in an underway project, the development of a Modula-2 compiler running on various UNIX boxes built on MIPS chips. That was my introduction to the fascinating world of compilation. I started by writing library code and translating interfaces from C to Modula-2, then I moved on to porting the compiler to the different vendor boxes, figuring out their idiosyncrasies.

Dave: Were you doing this work in Pascal? If not, when did you bring Pascal and Metrowerks together?

Marcel: The MIPS compilers used a frontend/backend architecture with the backend being proprietary which caused some problems. That led to our need to develop a compiler technology where we could hold rights both on the frontend and backend. At the same time we started another project on the Macintosh to provide a Pascal compiler along with tutorial and teaching material for Macmillan. That compiler was built around the Modula-2 package available then. So the new technology was meant to provide a solution for multiple frontends and multiple backends, and was supposed to be the replacement for these versions of Pascal and Modula-2. The chosen architecture was a derivative from the Oberon architecture developed in Zurich by Nicklaus Wirth’s team and was first targeted to the SPARC platform. I then implemented Pascal and Modula-2 on SPARC using that architecture. We then stopped the development of UNIX compilers and I inherited the Macintosh compilers where I unified the Pascal and Modula-2 code generators. Around this time it was decided that we needed a C compiler, the PowerPC was in the air and we received in the mail a terrific demo from Andreas. [To hear more about Andreas’s story, check back a few issues for the interview with Andreas Hommel.]

Dave: How did the Pascal compiler make the leap to CodeWarrior?

Marcel: At this point, we had a 68K C compiler with optimizations, a split frontend/backend design. Pascal is very strong in the developer community (still today FileMaker Pro is mostly written in Pascal and is built with CodeWarrior). CodeWarrior alone would only be Metrowerks C and wouldn’t provide the broader industrial completeness and strength that we wanted to provide. So we dropped the architecture used on the SPARC, which still didn’t support optimizations, and I got the Pascal frontend development plus backend/linker modifications, interfaces, libraries and utilities. DR/1 was to ship in January with the scheduled launch of the first Power Macintoshes. In the mean time, I dropped my Masters and stopped teaching. I was giving lectures at the university for the past few months along with working on my Masters and working part-time on Metrowerks compilers.

MPW Pascal was the chosen dialect because it’s the de facto standard Pascal dialect on Macintosh. THINK Pascal wasn’t supported and relates heavily to MPW Pascal except for a few minor differences. The biggest problem involved in developing CodeWarrior Pascal was the universal interfaces. Since Apple decided not to support Pascal anymore, the new interfaces developed for the introduction of the PowerPC were made, keeping the PowerPC calling conventions in mind and making use of C’s syntactic capabilities (for example, the CONST keyword is meant to specify an invariant pointer parameter and doesn’t have a Pascal equivalent).

The change from 68K to PPC calling conventions was dramatic for Pascal as the passing of value records and arrays are not the same. There were two possibilities: either support the 68K calling conventions on the PowerPC (thus breaking the calling conventions adopted for all languages, which were inherited from IBM’s AIX machines and provide a seamless common way of doing cross-language, cross-vendor routine calls) or modify the interfaces to render the expected parameter passing. The 68K conventions pass every record and array bigger than 4 bytes by passing a pointer. The PowerPC passes value records into registers and on the stack, and all arrays by pointer regardless of the size. To be able to match both PowerPC and 68K conventions with the same set of interfaces could have been achieved by using a new parameter passing method using the CONST keyword that would have the semantics of a value parameter and an efficient passing implementation. This solution wasn’t taken because it would have broken some compilers. The retained solution was to use VAR parameters because they force the use of pointers, but it has the drawback of breaking some user code, especially in the case of packed arrays and records.

The other problem encountered on the PowerPC is the signatures. They are packed arrays of 4 chars, so they’d have to be passed by pointer. But their C equivalent is an unsigned long, thus value not pointers. To get this to work I had to introduce on PowerPC an UNSIGNEDLONG data type that’s compatible with packed arrays of 4 chars so OSTYPE can be used without problems. After 2 years of use, this solution to the Universal Interfaces problem has proven to be the right one. Another conclusion that comes up is the need to add a procedural data type to Pascal. The new data type enables the compiler to do type checking on the callback routines that get passed either to user code or the toolbox. This type checking capability has proven to be very effective in the porting of code from 68K to PowerPC.

Dave: So at this point, we have the first CodeWarrior IDE with Pascal and C/C++. Since plugins weren’t introduced till CW6/7, how did the Pascal compiler work?

Marcel: The first releases of CodeWarrior didn’t used the plugins architecture but a common IDE was always in the air as the cornerstone of CodeWarrior. The new PowerPC machines had more resources and made such a design more interesting for an entire IDE. So along with the C/C++ compiler, the Pascal compiler was compiled and linked along with the IDE sources. It wasn’t that the Macintoshes were too slow or the resources poor, it was just that it wasn’t the way to do things. People knew about their machine constraints and didn’t go for blue sky, so the applications were kind of in scale with the hardware capabilities. Now that we have faster and bigger machines it is possible to add on facilities to the programs and these added facilities eat up not only disk space but also memory. So having the ability to load on demand various parts of a program has been around almost as long as computers. It’s the way of doing it that changes over time and across platforms.

Dave: Can You talk about the difference between the C++ “value model” and Object Pascal’s “reference” model?

Marcel: The object model is the underlying runtime model that affects the aspect and behavior of objects. In Object Pascal the object model used is known as the reference model because you have to explicitly invoke the creation and deletion of objects. On the other hand, C++ and Turbo Pascal use the value model which involves far more complex semantics for manipulating objects. People often mix method binding with the object model. This accounts for some misconceptions. In Object Pascal, the language only allows compile time binding determination for ‘inherited’ method calls. All the other methods can be overridden, thus forcing late binding which can be changed by a clever linker for monomorphic methods (methods that are never overridden within the program).

In C++, member functions need the ‘virtual’ keyword to specify polymorphism, thus helping the compiler decide how to perform the method call. (It gets more complicated when multiple inheritance is involved.) This binding facility is partially lifted by the introduction of procedural types in CodeWarrior Pascal, but still has to be hand constructed along with the data fields when the object gets created. The difference between object models comes to light when you look at the copy semantics. In Object Pascal, assigning one object to another, passing it as a value parameter or returning one as a function result doesn’t create a new instance as in C++ (and associated copy constructors) or as in Turbo Pascal (bug prone object casting), but only copies a reference. In Object Pascal cloning an object requires a method call and is explicit. This greatly simplifies the complexity of the program without limiting the functionality.

Dave: What are some of the differences between CodeWarrior Object Pascal and other dialects of Object Pascal?

Marcel: There are as many Pascal dialects as there are vendors. One of the biggest contenders is Turbo Pascal. The differences can be categorized into three fields; runtime support (mostly IO and platform specific stuff), the enhanced syntax, and finally the class and object models. We’ve already discussed the object model. The most apparent IO difference between Object Pascal and Turbo Pascal is TP’s assign routine, which binds a logical file to a physical file. Under Object Pascal this is performed directly by the opening routines.

The other IO differences lie in file access semantics, mostly for the handling of binary files. The original Pascal’s (and also the ANS standard) way of dealing with them is using get/put and direct file access thru the caret operator ‘file^’. The object support is very different. OP implements a very simple syntax that hasn’t evolved in about 10 years, whereas TP went through a constant evolution of their implementation. This is clearly an area where we have to expand OP’s capabilities because it really represents an advantage to programmers to have a more flexible implementation.

Dave: What are you working on now?

Marcel: My group is currently working on a Windows version of CodeWarrior Pascal. We are also developing a tool that will automate the use of C precompiled headers within Pascal as Pascal support is more and more lacking within Apple and nonexistent on Windows.

Dave: What do see in the future for yourself and for Pascal?

Marcel: I think in the near future we’re going to see some kind of reevaluation of project development using C/C++ as metrics, and studies are going to circulate. I think that there could be some kind of backlash toward Pascal and Ada if the figures show that C/C++ didn’t deliver the expected results. As far as Pascal goes, from the market share perspectives, Pascal is a player in the academic market as most attempts to move to C and C++ didn’t work very well.

On the other hand, in software engineering things are different. Pascal would have to evolve much faster to meet today’s software engineering needs and standardize on a wide variety of platforms. Even then I’m not too sure about the prospects. As for me, I’m linked to Pascal as I want to evolve CodeWarrior’s implementation of Object Pascal to be a player in both the Macintosh and Windows Pascal market.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

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
Tinderbox 6.3.1 - Store and organize you...
Tinderbox is a personal content management assistant. It stores your notes, ideas, and plans. It can help you organize and understand them. And Tinderbox helps you share ideas through Web journals... 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 »
Tap Delay (Music)
Tap Delay 1.0.0 Device: iOS Universal Category: Music Price: $4.99, Version: 1.0.0 (iTunes) Description: Back in the “old days”, producers and engineers created delay and echo effects using tape machines. Tap Delay combines the warm... | Read more »
This Week at 148Apps: July 20-24, 2015
July is Heating Up With 148Apps How do you know what apps are worth your time and money? Just look to the review team at 148Apps. We sort through the chaos and find the apps you're looking for. The ones we love become Editor’s Choice, standing out... | Read more »

Price Scanner via MacPrices.net

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
12-inch MacBooks in stock for $20 off, save o...
Adorama has 12″ Retina MacBooks in stock for $20 off MSRP including free shipping plus NY & NJ sales tax only. For a limited time, Adorama will include a free Apple USB-C to USB Adapter, free 4-... Read more
College Student Deals: Additional $100 off Ma...
Take an additional $100 off all MacBooks and iMacs at Best Buy Online with their College Students Deals Savings, valid through August 8, 2015. Anyone with a valid .EDU email address can take... Read more
2015 13-inch 2.7GHz Retina MacBook Pro on sal...
B&H Photo has the new 2015 13″ 2.7GHz/128GB Retina MacBook Pro on sale today for $1199 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
2.8GHz Mac mini available for $988, includes...
Adorama has the 2.8GHz Mac mini available for $988, $11 off MSRP, including a free copy of Apple’s 3-Year AppleCare Protection Plan. Shipping is free, and Adorama charges sales tax in NY & NJ... Read more
Updated Mac Price Trackers
We’ve updated our Mac Price Trackers with the latest information on prices, bundles, and availability on systems from Apple’s authorized internet/catalog resellers: - 15″ MacBook Pros - 13″ MacBook... Read more
High-Precision Battery Fuel Gauge IC Extends...
Renesas Electronics Corporation has announced its new lithium-ion (Li-ion) battery fuel gauge IC, the RAJ240500, designed to extend battery life for connected mobile devices such as tablets, notebook... Read more
27-inch 3.3GHz 5K iMac on sale for $1799, $20...
B&H Photo has the 27″ 3.3GHz 5K iMac on sale for $1799 including free shipping plus NY tax only. Their price is $200 off MSRP, and it’s the lowest price available for this model from any Apple... Read more
Twelve South Free Dual Screen Backgrounds Co...
Twelve South has posted a second collection of travel Desktop photos, noting: For the Twelve South team, a vacation is never just a vacation. It’s a time to try out new prototypes on the road, visit... Read more
Apple Refurbished iMacs available for up to $...
The Apple Store has Apple Certified Refurbished iMacs available for up to $380 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 27″ 3.5GHz 5K iMac – $1949 $... Read more

Jobs Board

Engineering Manager, Search Relevance, *Appl...
**Job Summary** Apple 's new Spotlight Suggestions service provides fast, relevant search results from the Inte et in Spotlight and Safari on iOS and OS X. We are looking 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
*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* 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.