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.

TIP OF THE MONTH

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.

TSplashWindow::~TSplashWindow()
        {
        if (fSplashPicture)
                DisposeHandle((Handle) fSplashPicture);  // Oops!
        this->Close();
        }

TWindow::Close(void)
        {
        WindowPtr       newFrontWindow = nil;
        if (FrontNonFloatingWindow() == fWindow)
          newFrontWindow = (WindowPtr)((WindowPeek)fWindow)->nextWindow;
        this->Activate(false);
        DisposeWindow(fWindow);
        if (newFrontWindow)
           HiliteAndActivateWindow(newFrontWindow,true);
        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
gpowell@mv.us.adobe.com

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
mark_tillinghast@lamg.com

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)
#else
#define ReportError(err)  /* nothing */
#endif

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

Latest Forum Discussions

See All

Soft Drummer (Music)
Soft Drummer 1.0 Device: iOS Universal Category: Music Price: $14.99, Version: 1.0 (iTunes) Description: Soft Drummer is the closest thing to a pro session subtle drummer in your pocket. Easy to use and fast, it's much more than a... | Read more »
Is GO Gear the Pokemon GO map app you...
Now that we've settled into something of a Pokemon GO status quo, the number one desire of most players can best be summed out by modifying a quote from Rod Tidwell of Jerry Maguire: "Show me the Pokemon!" [Read more] | Read more »
Rodeo Stampede update: Mountains, new an...
The Savannah and Jungle were just the beginning in Rodeo Stampede. Get ready to head for the Mountains. I think I heard that in a beer ad once. [Read more] | Read more »
COSMOS RINGS (Games)
COSMOS RINGS 1.0.0 Device: iOS iPhone Category: Games Price: $5.99, Version: 1.0.0 (iTunes) Description: This game cannot be played without the Apple Watch.Released anniversary sale until August 31,2016 PST! A tragic tale of time's... | Read more »
How to get started selling on Mercari
As far as ecommerce has come over the last decade or so, there's still a tremendous opportunity to make it easier for people to buy and sell goods. That's especially true when it comes to shopping apps, which should only continue to increase in... | Read more »
Human Anatomy Atlas 2017 Edition - Compl...
Human Anatomy Atlas 2017 Edition - Complete 3D Human Body 1.0.24 Device: iOS iPhone Category: Medical Price: $24.99, Version: 1.0.24 (iTunes) Description: | Read more »
Heroes of Normandie (Games)
Heroes of Normandie 1.5 Device: iOS Universal Category: Games Price: $14.99, Version: 1.5 (iTunes) Description: The game does not support iPhone 4s and below | Read more »
Why you should never power up Pokemon in...
There's no question that candy is dandy in Pokemon GO. You need big quantities of it to evolve your Pokemon, and when combined with stardust, it can be used to power up your favorite pocket monsters as well, making them more formidable for the gym... | Read more »
Webzen launches 3D MMORPG MU Origin on i...
Mu Origin is featured time and time again at the very top of App Stores in China, and within the top five worldwide top-grossing charts on Google Play.Its popularity in Korea and China, featuring more than 120 registered players in China and 6... | Read more »
Severed (Games)
Severed 1.0 Device: iOS Universal Category: Games Price: $5.99, Version: 1.0 (iTunes) Description: LAUNCH DISCOUNT ON NOW!! ENDS AUGUST 4! ==== Take control of a one-armed warrior named Sasha, wielding a living sword on her journey... | Read more »

Price Scanner via MacPrices.net

9-inch 32GB Space Gray iPad Pro on sale for $...
B&H Photo has the 9″ 32GB WiFi Space Gray Apple iPad Pro on sale for $50 off MSRP including free shipping. B&H charges sales tax in NY only: - 9″ Space Gray 32GB WiFi iPad Pro: $549 $50 off... Read more
15-inch Retina MacBook Pros on sale for up to...
B&H Photo has 15″ Retina MacBook Pros on sale for up to $200 off MSRP. Shipping is free, and B&H charges NY tax only: - 15″ 2.2GHz Retina MacBook Pro: $1849 $150 off MSRP - 15″ 2.5GHz Retina... Read more
Second-Quarter Tablet Shipments Fell 4.8% –...
The latest report from the global market research firm TrendForce finds that worldwide tablet shipments for this second quarter totaled 33.54 million units, representing a quarterly drop of 4.8% and... Read more
Global Smartphone Sales Volumes Mark Second S...
According to preliminary results from the International Data Corporation (IDC) Worldwide Quarterly Mobile Phone Tracker, vendors shipped a total of 343.3 million smartphones worldwide in the second... Read more
Apple TVs on sale for $20-$40 off MSRP
Best Buy has 32GB and 64GB Apple TVs on sale for $20-$40 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-store... Read more
Mac minis on sale for $50-$100 off MSRP
B&H Photo has Mac minis on sale for $50 off MSRP including free shipping plus NY sales tax only: - 1.4GHz Mac mini: $449 $50 off MSRP - 2.6GHz Mac mini: $649 $50 off MSRP - 2.8GHz Mac mini: $949... Read more
Clearance 2015 13-inch MacBook Airs available...
B&H Photo has clearance 2015 13″ MacBook Airs available for $300 off original MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 1.6GHz/4GB/128GB MacBook Air (MJVE2LL/A): $799... Read more
Apple certified refurbished iPad mini 4s avai...
Apple has certified refurbished iPad mini 4s now available for up to $120 off the cost of new models. An Apple one-year warranty is included with each iPad, and shipping is free. The following models... Read more
Notebook Makers In No Rush To Adopt USB-C – R...
Digitimes’ Cage Chao and Joseph Tsai note that while the USB Type-C interface is enjoying growing popularity among smartphones and tablet makers, notebook and all-in-one (AIO) PC vendors (other than... Read more
iMacs on sale for up to $250 off MSRP
B&H Photo has 21″ and 27″ Apple iMacs on sale for up to $250 off MSRP including free shipping plus NY sales tax only: - 27″ 3.3GHz iMac 5K: $2049 $250 off MSRP - 27″ 3.2GHz/1TB Fusion iMac 5K: $... Read more

Jobs Board

*Apple* Retail - Bilingual - Multiple Positi...
…speaking a plus Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the Read more
Simply Mac *Apple* Specialist- Repair Techn...
…The Technician is a master at working with our customers to diagnose and repair Apple devices in a manner that exceeds the expectations set forth by Apple Read more
*Apple* Mobile Master - Best Buy (United Sta...
What does a Best Buy Apple Mobile Master do? At Best Buy, our mission is to leverage the unique talents and passions of our employees to inspire, delight, and enrich Read more
Best Buy *Apple* Computing Master - Best Bu...
What does a Best Buy Apple Computing Master do? At Best Buy our mission is to leverage the unique talents and passions of our employees to inspire, delight, and Read more
*Apple* Valley, CA School Speech Therapy Ope...
Apple Valley, CA School Speech Therapy Openings + Job Location: Apple Valley, CA + Category: Schools - SLP - CFY + Apply Now! + Back to Results Speech Language Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.