TweetFollow Us on Twitter

August 91 - Think Pascal 4

Think Pascal 4

Don Sawtelle

Having just expressed August's final proof back to Bill Anderson-lacking this page, of course-I have only to write this column, then it's on to October. Instead of writing an August issue overview, I'll describe a small useful workaround for failure handling with Think Pascal 4 (announced August 6th, and now shipping).

Just What you've been waiting for…

Think Pascal 4 runs under System 7 in both 24- and 32-bit modes, and works fine with virtual memory. It has all the headers required for writing System 7-savvy applications, and supports far code, making it possible to create applications that require up to 256k of jump table space. You can find out more about these and other new features by calling Symantec (617-275-4800)-or better yet, just order the upgrade. Oh, and project updates have been optimized; MacApp compiles noticeably faster.

…and Now 99% reliable

Think Pascal 4 is much more reliable when working with large MacApp applications than was Think Pascal 3. Think Pascal 3 had a serious flaw with respect to MacApp; if anything called Failure while running in the Think environment, and some of the routines on the stack at the time were compiled with the D option in the project window checked (so that you could source-debug them), Think Pascal was likely to crash. It would sometimes crash right away, and sometimes later, when you were no longer even thinking of your past failures. And projects could sometimes get corrupted, causing nasty problems that didn't go away until you removed the code from the project and rebuilt, or created a new project from scratch.

Because of all this, life was difficult when debugging anything with Think Pascal 3 that involved failure handling. The most useful technique for debugging failures-setting a stop sign at the beginning of the Failure procedure, so that you can see the context of the error before MacApp's failure handling cuts back the stack and displays the error dialog-caused Think Pascal 3 to crash when a failure occurred. I find it convenient to write code that uses failure handling even for recovery from soft (non-catastrophic) errors, so this was a real problem for me.

With the new release, Think Pascal 4 provides a couple of replacements for the MacApp failure library that you can use when debugging in the Think environment-one for use with the MacApp debugger, one for without. These libraries call a special trap that causes the Think Pascal debugging environment to do the cleanup it needs to for each routine that was on the stack at the time of a failure.

In my experience, with these special failure libraries, Think Pascal 4 is now almost 100% reliable. Most mysterious crashes of the Think environment eventually turn out to be my own runaway code trashing something that's none of its business. (Oh, for a protected memory space!) There are only two limitations: (1) you have to compile your entire application, including MacApp, with the Think debugging option on, because the special failure library isn't smart about not calling the Think cleanup code if a routine on the stack wasn't compiled with the Think debugging option; and (2) for some reason, which I hope Symantec technical support can eventually explain, a failure during application initialization(IMyApplication) still crashes Think Pascal, if you're using the special failure libraries.

The first limitation isn't serious unless your code runs too slowly when the entire application is compiled with Think debugging on. And it's safe to compile units that won't fail, and that don't call any routines which could fail, without Think debugging.

The second limitation seems to be the last remaining bit of Think Pascal's former unreliability that developers have lived with for so long. If your application does nothing complex during initialization, and your code doesn't have any bugs, you may not encounter the problem. I have an application that looks for devices during IMyApplication, and that uses failure handling as a way to gracefully handle their absence; if you do something like this, you'll be sure to repeatedly encounter the hard crash.

I've come up with a simple workaround. It's kind of odd, but it seems to circumvent the problem, and not cause any new ones, either.

How to keep the special failure library from crashing Think Pascal 4

First, make sure you have a correct TMyApplication.Initialize method that puts your application object in a state where it can be safely freed if something goes wrong. Actually, nothing will go wrong-famous last words-but just in case. Then, in your MMyApplication.p unit, call IApplication instead of IMyApplication. Also, change IMyApplication so that it doesn't call IApplication. Add a boolean to TMyApplication called fPostInitialize, set it to false in TMyApplication.Initialize, and override MacApp's PollEvent as shown in the PollEvent listing. With these changes, the significant initialization code for your application-the code that might fail-won't execute until MacApp's event handling loop runs for the first time. Thus you'll avoid the possibility of failure at a time when it could crash Think Pascal.

Do be sure to contain these changes within {$IFC} directives, so that it's easy to build your standalone application without them. This workaround is a hack that's just intended for using during debugging; you don't want it in your final code! n

 
AAPL
$524.94
Apple Inc.
+5.93
MSFT
$40.01
Microsoft Corpora
-0.39
GOOG
$536.10
Google Inc.
-20.44

MacTech Search:
Community Search:

Software Updates via MacUpdate

Tweetbot 1.5.1 - Popular iOS twitter cli...
Tweetbot is a full-featured OS X Twitter client with a lot of personality. Whether it's the meticulously-crafted interface, sounds and animation, or features like multiple timelines and column views... Read more
Mac DVDRipper Pro 4.1.7 - Copy, backup,...
Mac DVDRipper Pro is the DVD backup solution that lets you protect your DVDs from scratches, save your batteries by reading your movies from your hard disk, manage your collection with just a few... Read more
PDFpenPro 6.2 - Advanced PDF toolkit for...
PDFpenPro allows users to edit PDF's easily. Add text, images and signatures. Fill out PDF forms. Merge or split PDF documents. Reorder and delete pages. Even correct text and edit graphics! Create... Read more
PDFpen 6.2 - Edit and annotate PDFs with...
PDFpen allows users to easily edit PDF's. Add text, images and signatures. Fill out PDF forms. Merge or split PDF documents. Reorder and delete pages. Even correct text and edit graphics! Features... Read more
Monolingual 1.5.9 - Remove unwanted OS X...
Monolingual is a program for removing unnecesary language resources from OS X, in order to reclaim several hundred megabytes of disk space. It requires a 64-bit capable Intel-based Mac and at least... Read more
Maya 2015 - Professional 3D modeling and...
Maya is an award-winning software and powerful, integrated 3D modeling, animation, visual effects, and rendering solution. Because Maya is based on an open architecture, all your work can be scripted... Read more
Starcraft II: Wings of Liberty 1.1.1.180...
Download the patch by launching the Starcraft II game and downloading it through the Battle.net connection within the app. Starcraft II: Wings of Liberty is a strategy game played in real-time. You... Read more
Sibelius 7.5.0 - Music notation solution...
Sibelius is the world's best-selling music notation software for Mac. It is as intuitive to use as a pen, yet so powerful that it does most things in less than the blink of an eye. The demo includes... Read more
Typinator 5.9 - Speedy and reliable text...
Typinator turbo-charges your typing productivity. Type a little. Typinator does the rest. We've all faced projects that require repetitive typing tasks. With Typinator, you can store commonly used... Read more
MYStuff Pro 2.0.16 - Create inventories...
MYStuff Pro is the most flexible way to create detail-rich inventories for your home or small business. Add items to MYStuff by dragging and dropping existing information, uploading new images, or... Read more

Latest Forum Discussions

See All

Have a Special Dead Trigger 2 Easter Bas...
Have a Special Dead Trigger 2 Easter Basket Full of Goodies, Courtesy of Madfinger Games Posted by Rob Rich on April 18th, 2014 [ permalink ] Dead Trigger 2 | Read more »
Zynga Launches Brand New Farmville Exper...
Zynga Launches Brand New Farmville Experience with Farmville 2: Country Escape Posted by Tre Lawrence on April 18th, 2014 [ permalink ] | Read more »
David. Review
David. Review By Cata Modorcea on April 18th, 2014 Our Rating: :: MINIMALISTIC IN A DIFFERENT WAYUniversal App - Designed for iPhone and iPad David is a minimalistic game wrapped inside of a soothing atmosphere in which the hero... | Read more »
Eyefi Unveils New Eyefi Cloud Service Th...
Eyefi Unveils New Eyefi Cloud Service That Allows Users to Share Media Across Personal Devices Posted by Tre Lawrence on April 18th, 2014 [ permalink ] | Read more »
Tales from the Dragon Mountain: The Lair...
Tales from the Dragon Mountain: The Lair Review By Jennifer Allen on April 18th, 2014 Our Rating: :: STEADY ADVENTURINGiPad Only App - Designed for the iPad Treading a safe path, Tales from the Dragon Mountain: The Lair is a... | Read more »
Yahoo Updates Flickr App with Advanced E...
Yahoo Updates Flickr App with Advanced Editing Features and More Posted by Tre Lawrence on April 18th, 2014 [ permalink ] | Read more »
My Incredible Body - A Kid's App to...
My Incredible Body - A Kid's App to Learn about the Human Body 1.1.00 Device: iOS Universal Category: Education Price: $2.99, Version: 1.1.00 (iTunes) Description: Wouldn’t it be cool to look inside yourself and see what was going on... | Read more »
Trials Frontier Review
Trials Frontier Review By Carter Dotson on April 18th, 2014 Our Rating: :: A ROUGH LANDINGUniversal App - Designed for iPhone and iPad Trials Frontier finally brings the famed stunt racing franchise to mobile, but how much does its... | Read more »
Evernote Business Notebook by Moleskin I...
Evernote Business Notebook by Moleskin Introduced – Support Available in Evernote for iOS Posted by Tre Lawrence on April 18th, 2014 [ permalink ] | Read more »
Sparkle Unleashed Review
Sparkle Unleashed Review By Jennifer Allen on April 18th, 2014 Our Rating: :: CLASSY MARBLE FLINGINGUniversal App - Designed for iPhone and iPad It’s a concept we’ve seen before, but Sparkle Unleashed is a solidly enjoyable orb... | Read more »

Price Scanner via MacPrices.net

iMacs on sale for up to $160 off MSRP this we...
Best Buy has iMacs on sale for up to $160 off MSRP for a limited time. Choose free home shipping or free instant local store pickup (if available). Prices are valid for online orders only, in-store... Read more
iPad Airs on sale this weekend for up to $100...
Best Buy has WiFi iPad Airs on sale for $50 off MSRP and WiFi + Cellular iPad Airs on sale for $100 off MSRP on their online store for a limited time, with prices now starting at $449. Choose free... Read more
Apple restocks refurbished Mac minis starting...
The Apple Store has restocked Apple Certified Refurbished Mac minis for up to $150 off the cost of new models. Apple’s one-year warranty is included with each mini, and shipping is free: - 2.5GHz Mac... Read more
Hyundai Brings Apple CarPlay To The 2015 Sona...
Hyundai Motor America has announced it will bring Apple CarPlay functionality to the 2015 Sonata. CarPlay is pitched as a smarter, safer and easier way to use iPhone in the car and gives iPhone users... Read more
Updated iPads Coming Sooner Than We Had Thoug...
MacRumors, cites KGI securities analyst Ming Chi Kuo, well-respected as an Apple product prognisticator, saying that Apple will introduce an upgraded iPad Air and iPad mini in 2014/Q3, meaning the... Read more
Toshiba Unveils New High And Low End Laptop M...
Toshiba has announced new laptop models covering both the high-end and low-end of the notebook computer spectrum. Toshiba 4K Ultra HD Laptop Toshiba’s new Satellite P55t features one of the world’s... Read more
Save up to $270 with Apple refurbished 13-inc...
The Apple Store has Apple Certified Refurbished October 2013 13″ Retina MacBook Pros available starting at $1099, with models up to $270 off MSRP. Apple’s one-year warranty is standard, and shipping... Read more
Apple now offering refurbished iPad mini with...
The Apple Store has Certified Refurbished 2nd generation iPad minis with Retina Displays now available starting at $339. Apple’s one-year warranty is included with each model, and shipping is free.... Read more
Microsoft Blinks – Drops Microsoft Office 365...
Microsoft has dropped the annual subscription fee for Microsoft Office 365 Personal – which is needed in order to create and edit documents in Microsoft Office for iPad. However, Apple’s iOS and OS X... Read more
New AVG Vault Apps for iOS and Android Help K...
AVG Technologies N.V. an online security company for 177 million active users, has announced the launch of its latest mobile application, AVG Vault. The free app introduces an innovative user... Read more

Jobs Board

*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Retail - Manager - Holyoke - Apple I...
Job Summary Keeping an Apple Store thriving requires a diverse set of leadership skills, and as a Manager, you’re a master of them all. In the store’s fast-paced, Read more
*Apple* Retail - Manager - Apple (United Sta...
Job SummaryKeeping an Apple Store thriving requires a diverse set of leadership skills, and as a Manager, you're a master of them all. In the store's fast-paced, dynamic Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Retail - Market Leader - Cincinnati...
…challenges of developing individuals, building teams, and affecting growth across Apple Stores. You demonstrate successful leadership ability - focusing on excellence Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.