TweetFollow Us on Twitter

May 95 Tips
Volume Number:11
Issue Number:5
Column Tag:Tips & Tidbits

Tips & Tidbits

By Scott T Boyd, Editor

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


Flush Out Your Bugs

Before releasing an application to your testers, load these three extensions: EBBE (Even Better Bus Error), DisposeResource, and DoubleTrouble. They check for NIL dereferences, improperly-disposed resources, and multiply-disposed memory manager blocks. [You can find these extensions in many places, including our ftp and other online sites - Ed stb] Run your application. You may be surpised at what you find.

Using these debugging tools, I caught a bug in an application based on the 1/18/95 release of Sprocket. This bug was fixed in the 1/25/95 Sprocket release, and does not exist in the 12/94 release. I’m using this code both as an example and a suggested patch if you are using the 1/18 version of Sprocket.

        if (fSplashPicture)
                DisposeHandle((Handle) fSplashPicture);  // Oops!

        WindowPtr       newFrontWindow = nil;
        if (FrontNonFloatingWindow() == fWindow)
          newFrontWindow = (WindowPtr)((WindowPeek)fWindow)->nextWindow;
        if (newFrontWindow)
        return true;

When I ran the executable, I dropped into my low level debugger, and looked at the stack. Return addresses on the stack from the MacsBug stack crawl sc7:

  Stack Addr  Frame Addr   Caller
   01C6ECD0               01B6D6D2 'CODE 0001 2690 Sprocket Lib'+0172
   01C6ECC8               01B6D692 'CODE 0001 2690 Sprocket Lib'+0132
   01C6ECAA    01C6ECA6   01B6E9F8 main+01F2
   01C6EC9E    01C6EC9A   01B6EF7A TSplashWindow::~TSplashWindow()+002C
   01C6EC88               01B6FA3C TWindow::Close()+0034
   01C6EC80    01C6EC7C   408578C4 _DisposeWindow+0004
   01C6EC6C               4085A846 _FrontWindow+0096
   01C6EC54               40877EB4 _KillPicture+0004
   01C6EC40               4085785C _NewWindow+010C
   01C6EC34               40877EB4 _KillPicture+0004
   01C6EC30               4085785C _NewWindow+010C

From this stack trace I saw that fSplashPicture got disposed again by DisposeWindow(fWindow); A review of the code showed the offending extra Dispose in ~TSplashWindow().

Why not leave these debugging resources on your system all the time? Well, it appears that not everyone uses these tools religiously and several other of my favorite (nameless) applications write to location Zero and trigger EBBE. I’ve sent in bug reports to the offenders, but I am still waiting for all the update releases.

Happy Bug Trails!

- Gary W. Powell

Powering Up The RTM Instruction

For you power programmers out there, here’s a little tip on taking advantage of the PowerPC architecture. Where you might have used the 68020 RTM instruction (Return from Module), you can get a lot of mileage by using the new PowerPC RTFM instruction instead. We can assure you that you will save literally hours of time.

- David Gorkan and Allan Foster

Save a Little Time

Here is a great and easy way to supercharge File Open... File Save and File Save As... operations from any application, especially if you use the Apple Menu Items to store aliases to folders: Make an alias of the Apple Menu Items folder and put it on the Desktop.

What does that get you? Well, since the Standard file Get and Put Dialogs all have a Desktop button, you can easily get to the Apple Menu Items, and hence access any aliases that are stored there. Just Click on the Desktop folder and the Apple Menu Item Alias appears as a supercharged Volume of Aliases.

But wait, there’s more! You get a real bonus from using System 7.5 because, if you put the Apple Menu Items alias onto the desktop, System 7.5 maintains automated folders, so the Apple Menu Items Alias can be used to get to “Recent Documents”. The “Recent Servers” can be used to log onto to any server without leaving the application that you are running.

- Mark Tillinghast
XXCAL, Testing And Systems Division

Debugging For Fun and Profit

When you have routines that return OSErrs, finish them with the following bit of code:

ReportError ( err );
return err;

which is defined as:

#ifdef qDEBUG
#define ReportError(err) do { if (err != noErr ) DebugStr ( “
\pError” ); } while (false)
#define ReportError(err)  /* nothing */

With this macro, you can tell every time that one of your routines returns an error, and it’s easy to follow your error handling code.

- Marshall Clow
Aladdin Systems

What’s My Modifier?

To quickly get the status of modifier keys, use these simple lines:

typedef struct kbd_bits {
 int command : 1;
 int : 5;
 int space : 1;
 int tab : 1;
 int : 4;
 control : 1;
 option : 1;
 capslock : 1;
 shift : 1;
} kbd_bits;

#define KeyModifiers (*(kbd_bits *)0x17A)

Then you can say simply:

if (KeyModifiers.control) {
 Debugger(); // drop into a debugger

This works across all Macs, including foreign versions and keyboard maps. For maximum compatibility with a minimal speed hit, call GetOSEvent with a null event mask and examine the modifiers field of the event returned.

- Jorg Brown
The Mac Group


Community Search:
MacTech Search:

Software Updates via MacUpdate

Planet Diver guide - How to survive long...
Planet Diver is an endless arcade game about diving through planets while dodging lava, killing bats, and collecting Starstuff. Here are some tips to help you go the distance. [Read more] | Read more »
KORG iDS-10 (Music)
KORG iDS-10 1.0.0 Device: iOS iPhone Category: Music Price: $9.99, Version: 1.0.0 (iTunes) Description: ** Debut Discount: 50% OFF! Sale Price US$9.99 (Regular price US$19.99). Other all Korg apps are also 50% OFF until Dec 28! **... | Read more »
World of Tanks Generals guide - Tips and...
World of Tanks Generals is a brand new card game by the developer behind the World of Tanks shooter franchise. It plays like a cross between chess and your typical card game. You have to keep in consideration where you place your tanks on the board... | Read more »
TruckSimulation 16 guide: How to succeed...
Remember those strangely enjoyable truck missions in Grand Theft Auto V whereit was a disturbing amount of fun to deliver cargo? TruckSimulation 16 is reminiscent of that, and has you play the role of a truck driver who has to deliver various... | Read more »
The best GIF making apps
Animated GIFs have exploded in popularity recently which is likely thanks to a combination of Tumblr, our shorter attention spans, and the simple fact they’re a lot of fun. [Read more] | Read more »
The best remote desktop apps for iOS
We've been sifting through the App Store to find the best ways to do computer tasks on a tablet. That gave us a thought - what if we could just do computer tasks from our tablets? Here's a list of the best remote desktop apps to help you use your... | Read more »
Warhammer 40,000: Freeblade guide - How...
Warhammer 40,000: Freebladejust launched in the App Store and it lets you live your childhood dream of blowing up and slashing a bunch of enemies as a massive, hulking Space Marine. It's not easy being a Space Marine though - and particularly if... | Read more »
Gopogo guide - How to bounce like the be...
Nitrome just launched a new game and, as to be expected, it's a lot of addictive fun. It's called Gopogo, and it challenges you to hoparound a bunch of platforms, avoiding enemies and picking up shiny stuff. It's not easy though - just like the... | Read more »
Sago Mini Superhero (Education)
Sago Mini Superhero 1.0 Device: iOS Universal Category: Education Price: $2.99, Version: 1.0 (iTunes) Description: KAPOW! Jack the rabbit bursts into the sky as the Sago Mini Superhero! Fly with Jack as he lifts impossible weights,... | Read more »
Star Wars: Galaxy of Heroes guide - How...
Star Wars: Galaxy of Heroes is all about collecting heroes, powering them up, and using them together to defeat your foes. It's pretty straightforward stuff for the most part, but increasing your characters' stats can be a bit confusing because it... | Read more »

Price Scanner via

World’s First USB-C Adapter For MacBook Suppo...
Innergie, a brand of Delta Electronics, has announced its official release of the world’s first USB-C adapter supporting four DC output voltages, the PowerGear USB-C 45. This true Type C adapter... Read more
13-inch and 11-inch MacBook Airs on sale for...
B&H Photo has 13″ and 11″ MacBook Airs on sale for up to $120 off MSRP as part of their Holiday sale including free shipping plus NY sales tax only: - 11″ 1.6GHz/128GB MacBook Air: $819 $90 off... Read more
13-inch MacBook Pros on sale for up to $150 o...
Take up to $150 off MSRP on the price of a new 13″ MacBook Pro at B&H Photo today as part of their Holiday sale. Shipping is free, and B&H charges NY tax only. These prices are currently the... Read more
13-inch 128GB MacBook Air now on sale for $79...
Best Buy has just lowered their price on the 2015 13″ 1.6GHz/128GB MacBook Air to $799.99 on their online store for Cyber Monday. Choose free shipping or free local store pickup (if available). Sale... Read more
Best Buy lowers 13-inch MacBook Pro prices, n...
Best Buy has lowered prices on select 13″ MacBook Pros this afternoon. Now save up to $200 off MSRP for Cyber Monday on the following models. Choose free shipping or free local store pickup (if... Read more
Cyber Monday: Apple MacBooks on sale for up t...
Apple resellers have MacBook Pros, MacBook Airs, and MacBooks on sale for up to $250 off MSRP for Cyber Monday 2015. The following is a roundup of the lowest prices available for new models from any... Read more
Cyber Monday: Apple Watch on sale for up to $...
B&H Photo has the Apple Watch on sale for Cyber Monday for $50-$100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - Apple Watch Sport: $50 off - Apple Watch: $50-$100 off B... Read more
Cyber Monday: 15% off Apple products, and sto...
Use code CYBER15 on Cyber Monday only to take 15% on Apple products at Target, and store-wide. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-... Read more
iPad Air 2 And iPad mini Among Top Five Black...
Adobe has released its 2015 online shopping data for Black Friday and Thanksgiving Day. The five best selling electronic products on Black Friday were Samsung 4K TVs, Apple iPad Air 2, Microsoft Xbox... Read more
All-in-one PC Shipments Projected To Drop Ove...
Digitimes’ Aaron Lee and Joseph Tsai report that all-in-one (AIO) PC shipments may drop a double-digit percentage on-year in 2015 due to weaker-than-expected demand, although second-largest AIO make... Read more

Jobs Board

*Apple* New Products Tester Needed - Apple (...
…we therefore look forward to put out products to quality test for durability. Apple leads the digital music revolution with its iPods and iTunes online store, continues Read more
Software Engineer, *Apple* Watch - Apple (U...
# Software Engineer, Apple Watch Job Number: 33362459 Santa Clara Valley, Califo ia, United States Posted: Jul. 28, 2015 Weekly Hours: 40.00 **Job Summary** Join the Read more
SW Engineer - *Apple* Music - Apple (United...
# SW Engineer - Apple Music Job Number: 40899104 San Francisco, Califo ia, United States Posted: Aug. 18, 2015 Weekly Hours: 40.00 **Job Summary** Join the Android Read more
Sr Software Engineer *Apple* Pay - Apple (U...
# Sr Software Engineer Apple Pay Job Number: 44003019 Santa Clara Valley, Califo ia, United States Posted: Nov. 13, 2015 Weekly Hours: 40.00 **Job Summary** Apple Read more
*Apple* Site Security Manager - Apple (Unite...
# Apple Site Security Manager Job Number: 42975010 Culver City, Califo ia, United States Posted: Oct. 2, 2015 Weekly Hours: 40.00 **Job Summary** The Apple Site Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.