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

GraphicConverter 11.2.2 - $39.95
GraphicConverter is an all-purpose image-editing program that can import 200 different graphic-based formats, edit the image, and export it to any of 80 available file formats. The high-end editing... Read more
VueScan 9.7.30 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Things 3.12.6 - Elegant personal task ma...
Things is a task management solution that helps to organize your tasks in an elegant and intuitive way. Things combines powerful features with simplicity through the use of tags and its intelligent... Read more
Skim 1.5.11 - PDF reader and note-taker...
Skim is a PDF reader and note-taker for OS X. It is designed to help you read and annotate scientific papers in PDF, but is also great for viewing any PDF file. Skim includes many features and has a... Read more
Navicat Premium Essentials 15.0.20 - Pro...
Navicat Premium Essentials is a compact version of Navicat which provides basic and necessary features you will need to perform simple administration on a database. It supports the latest features... Read more
Affinity Photo 1.8.4 - Digital editing f...
Affinity Photo - redefines the boundaries for professional photo editing software for the Mac. With a meticulous focus on workflow it offers sophisticated tools for enhancing, editing and retouching... Read more
EtreCheck Pro 6.3 - For troubleshooting...
EtreCheck is an app that displays the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to... Read more
beaTunes 5.2.11 - Organize your music co...
beaTunes is a full-featured music player and organizational tool for music collections. How well organized is your music library? Are your artists always spelled the same way? Any R.E.M. vs REM?... Read more
Bookends 13.4.4 - Reference management a...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Bookends uses the cloud to sync reference libraries on all the Macs you use.... Read more
Affinity Designer 1.8.4 - Vector graphic...
Affinity Designer is an incredibly accurate vector illustrator that feels fast and at home in the hands of creative professionals. It intuitively combines rock solid and crisp vector art with... Read more

Latest Forum Discussions

See All

Global Spy is an intriguing 2D spy sim f...
Developer Yuyosoft Innovations' Global Spy launched last month for iOS and Android, though if you missed it at the time, we're here to tell you why it's well worth a go. This one's all about international espionage, tracking down elusive spies,... | Read more »
Distract Yourself With These Great Mobil...
There’s a lot going on right now, and I don’t really feel like trying to write some kind of pithy intro for it. All I’ll say is lots of people have been coming together and helping each other in small ways, and I’m choosing to focus on that as I... | Read more »
Hyena Squad is sci-fi turn-based strateg...
Wave Light Games has just revealed its latest release, Hyena Squad, a turn-based RPG set in a space station infested by gross aliens and the living dead. The announcement was first reported on by Touch Arcade. [Read more] | Read more »
Idle Guardians: Never Die is a pixel art...
SuperPlanet has been fairly prolific with game releases so far this year with both Evil Hunter Tycoon and Lucid Adventure releasing earlier this year. Now, they've released another idle RPG called Idle Guardians: Never Die, which you can download... | Read more »
Ruinverse, Kemco's latest RPG, now...
Kemco's latest RPG endeavour, Ruinverse, initially launched for both iOS and Android earlier this month. It was released as a premium title that also had additional in-app purchases. Now, the developers have decided to release a freemium version... | Read more »
The 5 Best Mobile Platformers
Touch screens and action-oriented gameplay don't typically mix, but over the course of pondering the best platformers on mobile, I found myself having a really hard time picking just five. Quite a few developers have found really creative ways to... | 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 »
Endless runner Monster Dash will relaunc...
Remember Monster Dash? Well, it's set to return to a mobile device near you after having been pulled from stores in 2017 to meet GDPR compliance. This one first launched all the way back in August of 2010. Over ten years later, it's heading into... | Read more »
Auto Battle Chess is a colourful genre s...
Auto Battle Chess is an interesting hodgepodge of genres that aims to offer the ultimate auto chess experience. That's a pretty tall order, though with the game now out for Android, I suppose we don't have to wait to see if it lives up to its... | Read more »
Tom and Jerry: Chase hits 1 million pre-...
NetEase's 1v4 asymmetrical multiplayer game Tom and Jerry: Chase recently became available to pre-order for both iOS and Android in Southeast Asia. It's clearly proving to be a highly anticipated title too since it has now reached 1 million pre-... | Read more »

Price Scanner via MacPrices.net

Expercom offers $320 discount on the 6-core 1...
Apple reseller Expercom has the Silver 16″ 6-core MacBook Pro on sale for a limited time for $2079 shipped. Their price is $320 off Apple’s MSRP for this model, and it’s the cheapest price currently... Read more
Apple announces Education pricing for new 202...
Purchase a new 2020 iMac or iMac Pro at Apple using Apple’s Education discount, and take up to $400 off MSRP. All teachers, students, and staff of any educational institution with a .edu email... Read more
Apple reseller Expercom offers $256 discount...
Expercom has Apple’s new 2020 10-core iMac Pro available for order and on sale for $4743 shipped. Their price is $256 off Apple’s MSRP for this new model, and it’s the cheapest price we’ve seen so... Read more
Apple releases refreshed 2020 27″ iMacs with...
Apple today released updated versions of their 27″ iMacs featuring 10th generation Intel processors, SSDs across the board, a better 5K display, and improvements to the camera, speakers, and mic.... Read more
Xfinity Mobile promo: Take $200-$350 off Appl...
New customers can take $200 off the purchase of any new Apple iPhone model at Xfinity Mobile through 8/17/20. Service plan required. Existing customers can purchase an iPhone and receive $200 back in... Read more
B&H now offering $100-$200 discount on Ap...
B&H Photo has new 2020 13″ 2.0GHz MacBook Pros on sale for $100-$200 off Apple’s MSRP, starting at $1649. These are the same MacBook Pros sold by Apple in their retail and online stores, and B... Read more
Apple’s 6-Core Mac mini is on sale at Amazon...
Amazon has Apple’s new 2020 6-Core Mac mini on sale for $926.25 for a limited time. Their price is $173 off Apple’s $1099 MSRP for this model and includes a $48.75 instant discount available on their... Read more
New 2020 11″ iPad Pros on sale for $50-$75 of...
Apple reseller Expercom has new 2020 11″ Apple iPad Pros on sale for $50-$75 off MSRP, with prices starting at $749. These are the same iPad Pros sold by Apple in their retail and online stores: – 11... Read more
Switch to US Cellular and get a new Apple iPh...
US Cellular has Apple’s 2020 iPhone SE on sale for $350 off for new lines of service and a US Cellular unlimited plan. Promotion comes via monthly bill credits over a 30 month period. Their deal... Read more
Apple AirPods with Wireless Charging Case on...
Amazon has Apple’s AirPods with Wireless Charging Case on sale today for only $139.98 shipped. That’s $60 off Apple’s MSRP and the lowest price we’ve ever seen for these AirPods. Sale valid for a... Read more

Jobs Board

Director, Product Management - Lead *Apple*...
…better business results. **Job Title** Director, Product Management - Lead Apple / Token Requestor Services Overview The Mastercard Digital Enablement Services Read more
*Apple* Computing Professional - Store 286 (...
**770445BR** **Job Title:** Apple Computing Professional - Store 286 (Canton) **Job Category:** Store Associates **Store Number or Department:** 000286-Canton-Store Read more
Department Manager- Tech Shop/ *Apple* Stor...
…their parents want, and our faculty needs. As a Department Manager in our Tech Shop/ Apple Store you will spend the majority of your time on the sales floor engaging Read more
*Apple* Graders/Inspectors (Seasonal/Hourly/...
Title: Apple Graders/Inspectors (Seasonal/Hourly/No Benefits) # APPLE Location: US-VA-Winchester Read more
Tier 2 Technical Support Analyst - ( *Apple*...
…Analystiless than/strong>who will analyze and determine user software needs on all Apple devices (first support contact), Windows devices, and support printers in Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.