TweetFollow Us on Twitter

Nov 94 Tips
Volume Number:10
Issue Number:11
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.

Send us your tips! We’ll send you money, and developers all over the world will marvel at your insight, your wisdom, or the simple fact that you’ve got enough extra time to write and send a little bit of e-mail to make their lives a little bit better.

We pay $25 for every tip we use, and $50 for Tip of the Month. You can take your award in orders or subscriptions if you prefer. Make sure code compiles, and send tips by e-mail; editorial@xplain.com is a great address. See page two for our other addresses.

Tip Of The Month

Trapping Non-Trap Vector Calls

The Debugger has certain limitations in its ability to trace A-Line traps and such. As an example, suppose we’re interested in breaking on calls to CacheFlush. It’s a trap vector which is usually referenced by a JSR ([xx]) instead of the usual A-Line Trap vector. Because it doesn’t go through the normal A-line dispatcher, we can’t break on references to it with the Trap Intercept mechanism.

Here’s some example code that creates a dummy procedure in an application, and an initialization proc that patches the low-memory trap vector so that it points to the dummy procedure. I modify the dummy procedure to make it a JMP to the original value of the low memory vector [Remember, this is for debugging, not for shipping code. Shipping code should generally not modify code it’s about to execute - Ed stb]. Finally, the doPatch proc undoes the patch and restores the system to its previous state.

To use this, set a breakpoint at my_doPatch_Proc. When you drop into your debugger, look at the stack to see who’s calling. After some looking, you can automate the process by observing where the interesting return addresses are on the stack with an action clause (such as the one shown here) that would list them in the -Notes- window:

?ra := (ra7)^; { return addr is contents of A7 }

{ In the next line we check PC for an address in the Quadra 900 ROM }

if ?pc = 40887824 then ?ra := (ra7+#46+#28)^-2; { # = decimal } writeln(?ra:ProcPtr); { display the address as a proc name + offset }

resume;


/* 1 */
procedure my_doPatch_Proc; { make it at least 6 bytes long } 
begin 
end;

procedure doPatch(doit:Boolean); 
CONST jCacheFlush = $6f4; 
type  jmpL = record opc:integer; addr:Longint; end; 
VAR 
 q:^jmpL; 
 p:^Longint; 
begin
    p := pointer(jCacheFlush);{$06F4 is the low-mem global jCacheFlush}
    q := @my_doPatch_Proc;
    if doit then begin
 with q^ do begin 
 opc := $4EF9; {JMP.L} 
 addr := p^;  
 end;
   p^ := Ord(q);
 end
   else begin
        p^ := q^.addr;  { undo patch }
   end; 
end;

- Steve Jasik, Menlo Park, CA

Even Better Data Gathering

The September issue’s tip-of-the-month recommended a way to log standard information during crashes using the EveryTime MacsBug macro. This technique is particularly useful for beta sites to report bugs, but there’s an even easier way. Many versions of MacsBug already have a built-in macro called StdLog that does almost the same thing. Beta-sites can just use stdlog to supply you with information and it doesn’t require them to muck with their “Debugger Prefs” file.

- Harold Ekstrom, Walnut Creek, CA

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

iDefrag 5.0.0 - Disk defragmentation and...
iDefrag helps defragment and optimize your disk for improved performance. Features include: Supports HFS and HFS+ (Mac OS Extended). Supports case sensitive and journaled filesystems. Supports... Read more
PCalc 4.2 - Full-featured scientific cal...
PCalc is a full-featured, scriptable scientific calculator with support for hexadecimal, octal, and binary calculations, as well as an RPN mode, programmable functions, and an extensive set of unit... Read more
FileZilla 3.10.2 - Fast and reliable FTP...
FileZilla (ported from Windows) is a fast and reliable FTP client and server with lots of useful features and an intuitive interface. Version 3.10.2: Note: Now requires a 64-bit Intel processor.... Read more
The Hit List 1.1.11 - Advanced reminder...
The Hit List manages the daily chaos of your modern life. It's easy to learn - it's as easy as making lists. And it's powerful enough to let you plan, then forget, then act when the time is right.... Read more
Bartender 1.2.32 - Organize your menu ba...
Bartender lets you organize your menu bar apps. Features: Lets you tidy your menu bar apps how you want. See your menu bar apps when you want. Hide the apps you need to run, but do not need to... Read more
ClamXav 2.7.5 - Free virus checker, base...
ClamXav is a free virus checker for OS X. It uses the tried, tested, and very popular ClamAV open source antivirus engine as a back end. I hope you like and use ClamXav a lot and that it helps keep... Read more
xScope 4.1.2 - Onscreen graphic measurem...
xScope is powerful set of tools that are ideal for measuring, inspecting, and testing on-screen graphics and layouts. Its tools float above your desktop windows and can be accessed via a toolbar,... Read more
MacFamilyTree 7.3.3 - Create and explore...
MacFamilyTree gives genealogy a facelift: it's modern, interactive, incredibly fast, and easy to use. We're convinced that generations of chroniclers would have loved to trade in their genealogy... Read more
Skype 7.5.0.738 - Voice-over-internet ph...
Skype allows you to talk to friends, family and co-workers across the Internet without the inconvenience of long distance telephone charges. Using peer-to-peer data transmission technology, Skype... Read more
PushPal 3.0 - Mirror Android notificatio...
PushPal is a client for Pushbullet, which automatically shows you all of your phone's notifications right on your computer. This means you can see who's calling or read text messages even if your... Read more

It Came From Canada: Jurojin: Immortal N...
At this point it’s pretty safe to say that no MOBA is going to dethrone Dota 2 and League of Legends anytime soon. After all, if Batman can’t do it, nobody can. However, with a genre as popular and profitable as this one, there’s still room for... | Read more »
Tiny Farm – Animals, Tractors and Advent...
Tiny Farm – Animals, Tractors and Adventures! Review By Amy Solomon on March 3rd, 2015 Our Rating: :: LIVELY LANDSCAPESUniversal App - Designed for iPhone and iPad Tiny Farm – Animals, Tractors and Adventures! includes farm-related... | Read more »
This Week at 148Apps: February 23-27, 20...
Final February Fun at 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 »
GDC 2015 – Does Not Commute is Definitel...
GDC 2015 – Does Not Commute is Definitely a Game You Should Keep an Eye on Posted by Rob Rich on March 2nd, 2015 [ permalink ] We were teased about Mediocre Games’ (Smash Hit, | Read more »
F84 Games & POW! Announce Stan Lee V...
F84 Games has announced that it is working with legendary comic creator Stan Lee and POW! Entertainment to produce Stan Lee’s Hero Command. The game will be a action adventure of heroic proportions. | Read more »
Setlyst Keeps Your Set Straight So You C...
Setlyst Keeps Your Set Straight So You Can Focus On Rocking Out. Posted by Jessica Fisher on March 2nd, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Space is Vast, So Space Agency Has a Vas...
Space is Vast, So Space Agency Has a Vast New Update! Posted by Jessica Fisher on March 2nd, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Size DOES Matter Review
Size DOES Matter Review By Campbell Bird on March 2nd, 2015 Our Rating: :: HARD TO BEATUniversal App - Designed for iPhone and iPad This rhythm game has a unique control scheme and performance system that make it feel like a true... | Read more »
The first ever action 3D card battler Al...
On the other hand, you probably haven’t played an action 3D card battler – until now. Step forward, All Star Legion. All Star Legion is a 3D QTE-based action RPG card battler, but fear not – the game itself isn’t as convoluted as its description.... | Read more »
Travel Back to the 1980s With the Making...
Headup Games has released a hilarious making of video for its upcoming title, Pixel Heroes: Byte & Magic. The game is a RPG/Roguelike where you control three heroes set to save the township of Pixton from an evil cult called The Sons of Dawn.... | Read more »

Price Scanner via MacPrices.net

Sale! 15-inch 2.2GHz Retina MacBook Pro for $...
 Best Buy has the 15″ 2.2GHz Retina MacBook Pro on sale for $1774.99 $1799.99, or $225 off MSRP. Choose free home shipping or free local store pickup (if available). Price valid for online orders... Read more
27-inch 3.5GHz 5K iMac in stock today and on...
 B&H Photo has the 27″ 3.5GHz 5K iMac in stock today and on sale for $2299 including free shipping plus NY sales tax only. Their price is $200 off MSRP, and it’s the lowest price available for... Read more
Apple Launches Free Web-Based Pages and Other...
Apple’s new Web-only access to iWork productivity apps is a free level of iCloud service available to anyone, including people who don’t own or use Apple devices. The service includes access to Apple... Read more
Survey Reveals Solid State Disk (SSD) Technol...
In a recent SSD technology use survey, Kroll Ontrack, a firm specializing in data recovery, found that while nearly 90 percent of respondents leverage the performance and reliability benefits of SSD... Read more
Save up to $600 with Apple refurbished Mac Pr...
The Apple Store is offering Apple Certified Refurbished Mac Pros for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The... 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
Apple CEO Tim Cook to Deliver 2015 George Was...
Apple CEO Tim Cook will deliver the George Washington University’s Commencement address to GWU grads on May 17, at which time he will also be awarded an honorary doctorate of public service from the... Read more
Apple restocks refurbished Mac minis for up t...
The Apple Store has restocked Apple Certified Refurbished 2014 Mac minis, with models available starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: - 1.4GHz... Read more
Save up to $50 on iPad Air 2s, NY tax only, f...
 B&H Photo has iPad Air 2s on sale for $50 off MSRP including free shipping plus NY sales tax only: - 16GB iPad Air 2 WiFi: $469.99 $30 off - 64GB iPad Air 2 WiFi: $549 $50 off - 128GB iPad Air 2... Read more
16GB iPad Air 2 on sale for $447, save $52
Walmart has the 16GB iPad Air 2 WiFi on sale for $446.99 on their online store for a limited time. Choose free shipping or free local store pickup (if available). Sale price for online orders only,... Read more

Jobs Board

*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
*Apple* Pay Automation Engineer - iOS System...
**Job Summary** At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring passion and dedication to your job Read more
Sr. Technical Services Consultant, *Apple*...
**Job Summary** Apple Professional Services (APS) has an opening for a senior technical position that contributes to Apple 's efforts for strategic and transactional Read more
Event Director, *Apple* Retail Marketing -...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global engagement strategy and team. Delivering an overarching brand Read more
*Apple* Pay - Site Reliability Engineer - Ap...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.