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December 96 - MacApp Debugging Aids

MacApp Debugging Aids

Conrad Kopala

While working on Twist Down Lists, a recordable MacApp implementation of hierarchical lists, I developed several useful debugging aids for detecting memory leaks and access faults and managing memory usage problems. Here I describe how to use these debugging aids for more trouble-free MacApp programming.

In the article "Displaying Hierarchical Lists" in develop Issue 18, Martin Minow suggests that MacApp offers "flexible libraries for displaying and managing structured data." I accepted his challenge and decided to create a Twist Down Lists application with MacApp version 3.3.1. As complete as MacApp is, you still have to test your application to make sure it works. Among the problems I encountered, perhaps none were more frustrating than the insidious memory leak and the dreaded access fault. After discovering the nth memory leak and the mth access fault in my Twist Down Lists application, I decided that the situation was unacceptable -- there had to be a better way!

To solve these problems, I developed several debugging techniques. These techniques were useful to me, so I decided to share them with you in this article. Here are some of them:

  • Object counting lets you quickly discover memory leaks.

  • Memory display helps you gauge the size of a memory leak.

  • Object display helps you identify the cause of a memory leak and an access fault.

  • Object heap discipline helps your application manage tight memory situations by allowing you to erect a barrier to further expansion of the object heap.

  • Failure handling lets you force a failure in any spot in your code.

Accompanying this article on this issue's CD and develop's Web site is the complete Twist Down Lists application, which you can look at to see the implementation of all the debugging aids described in this article. Also provided are two engineering notes, "EN1 - Object Counting and Display" and "EN2 - Object Heap Discipline," which go into the gory details of implementing these debugging aids, and copies of the four MacApp files UObject.h, UObject.cp, PlatformMemory.h, and PlatformMemory.cp, which I modified to incorporate the debugging aids and which you can substitute for the original files (or similarly modify them yourself).

    Most of these debugging techniques are specifically for MacApp version 3.3.1. Later versions may already incorporate similar debugging features.*

OBJECT COUNTING

I've found object counting to be the fastest way to discover memory leaks. To maintain a running count of the number of objects in existence, I use a global variable named gObjectCount. Whenever a TObject is created or cloned, gObjectCount is incremented; when a TObject is destroyed, gObjectCount is decremented. The variable is incremented in the TObject constructor or TObject::ShallowClone and is decremented in the TObject destructor. To print the current value of gObjectCount, I use a global function named PrintObjectCount. You can call this function at any point in the application where you think it's useful. In my experience, one of the best places to test the value of gObjectCount is at the beginning of the function TYourApplication::DoSetupMenus. That point represents a set of stable application states that you should always be able to return to. By monitoring the value of gObjectCount as the application runs, you can obtain a set of characteristic values for gObjectCount. Any variation in these values should be investigated as a possible memory leak.

For example, for Twist Down Lists, the object count just after startup is 49. After a twistDownDocument is opened and closed, this count increases to 52. This increase is a consequence of adding a print handler to the view; a TPrintInfo and two TDependencies objects are created but never freed. Then, if you change the font size by choosing the Other menu item, the object count increases to 55. In this case, the TDialogTEView, TAdornerList, and TScroller objects are created when a new font size is entered in the TNumberText; they're never freed. Thereafter, the quiescent value of gObjectCount remains unchanged.

By using object counting, I've discovered TObject-based memory leaks in just minutes. To implement it, you need to make changes to UObject.h and UObject.cp, as described in "EN1 - Object Counting and Display." Or you can include the substitute UObject.h and UObject.cp files that I've provided.


MEMORY DISPLAY

My global function DisplayMemoryInfo displays the amount of free memory, the size of the temporary reserve, the size of the permanent reserve, the object heap size, the amount of memory available in the object heap, and the amount of object heap space used. If you have a memory leak, this function can give you information about the size of the leak. As with object counting, you can get a set of characteristic values as you run the application. The most useful of these indicators is the amount of object heap space used. In my experience, it makes the most sense to call this function at the beginning of the function TYourApplication::DoSetupMenus when you also display the object count. Realize that each time the object heap is expanded, an overhead of 20 bytes is incurred. As a result, the amount of object heap space slowly increases until the object heap reaches its maximum size. So if you see the amount of space used in the object heap increasing by some multiple of 20, it might just be attributable to object heap overhead.

To implement memory display, you need to make changes to UObject.h and UObject.cp, as described in "EN1 - Object Counting and Display." Or you can include the substitute UObject.h and UObject.cp files that I've provided.


OBJECT DISPLAY

While object counting and memory display let you quickly discover a memory leak, it's object display that helps you to identify the cause of the memory leak or an access fault. Turning on object display means that when a TObject-based object is constructed, a message -- including "who, what, and where" -- appears in the debugging window. Likewise, when the object is destroyed, a similar message appears.
    You can use a Simple Input-Output Window (SIOW) instead of your debugger's log window to display this information if you prefer.*
When an object is created, if object display is on, the debugger log window displays a message similar to the following:
Construct TSomeMacAppObject@ 0x2D6ACA4 Id=74 Size=108 ObjCnt = 73
#Construct TMyObject@ 0x2D6ACA4 Id=74 Size=108 ObjCnt = 73
When the object is destroyed, the log window displays a message like this:
#Destruct TMyObject@ 0x2D6ACA4 Id=74 Size=108 ObjCnt = 73
Destruct TSomeMacAppObject@ 0x2D6ACA4 Id=74 Size=108 ObjCnt = 73
Each line gives the class name of the object, its location in the object heap, its class ID, its size in bytes, and the current value of gObjectCount. In addition, the message tells you whether the object was created or destroyed.

So why are there two lines for construction and destruction? When an object like TMyObject is created, its TObject constructor is executed first, followed by the constructors for any MacApp objects in the descendant chain, ending with the constructor for TMyObject. In other words, objects are built from the bottom up. As each constructor does its thing, it's given the chance to display a message identifying itself. So when a new object is created, a series of messages is displayed that identify each stage of the construction process.

When the object TMyObject is destroyed, the process is reversed, with the destructor for TMyObject first displaying a message identifying itself, followed by the destructors for any MacApp objects in the descendant chain and ending with the destructor for TObject. Objects are destroyed from the top down.

Running an application with object display on provides a wealth of information about what an application is doing -- information that you can't get any other way. It's also a great way to find out what MacApp is doing. As described later in the section "Implementing Object Display," you can use flags to specify how much information to display.

DETECTING MEMORY LEAKS

Of course, when tracking down a memory leak, you're interested in finding an object that was created but never destroyed. To find this object, it's necessary to match object destructions with constructions. The leftover construction is the offending object that wasn't destroyed. You match constructions and destructions by using the addresses provided in the object display.
    Be careful when matching object destructions and constructions, because MacApp will reuse space in the object heap. I've often seen MacApp make a TAppleEvent, shortly thereafter free it, and then go on to make another TAppleEvent and store it at exactly the same address.*
If your debugger allows you to save the contents of the log window, sorting it on the address field would bunch all items with the same address together. That would make it much easier to match destructions with constructions. If you assign each object a serial number in its constructor, it would be even easier to do the matching.

Consider a real example. The MacApp example application IconEdit has a memory leak. (I found the leak because I used the application as a template.) Listing 1 shows the offending code.


Listing 1. An example of a memory leak

void TIconDocument::DoMenuCommand (CommandNumber aCommandNumber) 
{
   switch (aCommandNumber) {
      case cSetColor:
         {
            CRGBColor   newColor;
            CStr255      thePrompt = "Pick a new color";
            if (GetColor(kBestSystemLocation, thePrompt, fColor, 
                  newColor)) {
               if (TOSADispatcher::fgDispatcher->GetDefaultTarget()
                     ->IsRecordingOn()) {
                  TSetPropertyEvent *appleEvent = 
                      new TSetPropertyEvent;
                  appleEvent->ISetPropertyEvent(gServerAddress, 
                                 kAENoReply, this, pColor);
                  CTempDesc theNewColor;
                  theNewColor.PutRGBColor(newColor);
                  appleEvent->WriteParameter(keyAEData, theNewColor);
                  appleEvent->Send();   // <-- the problem
               }
               else {
                  TSetColorCommand *aSetColorCommand = 
                                       new TSetColorCommand();
                  aSetColorCommand->ISetColorCommand(this, newColor);
                  PostCommand(aSetColorCommand);
               }
            }
         }
         break;
      default:
         Inherited::DoMenuCommand(aCommandNumber); 
         break; 
   }
} 

With object counting and display, it took only minutes to discover the leak and identify the offending objects. Deciding how to eliminate the leak took a little longer. The leak arises because TAppleEvent::Send returns a reply TAppleEvent and neither it nor the TAppleEvent that was sent is freed. This leak is fixed by using the code snippet

TAppleEvent * theReply = theEvent->Send();
FreeIfObject(theEvent);
FreeIfObject(theReply);
in place of
appleEvent->Send();
Listing 1 is an example of a small memory leak, only 64 bytes. Because of its small size, it's virtually undetectable by means other than object display. These small memory leaks are a very serious problem because they fragment the object heap. Suppose that every time a command is executed, a 64-byte memory leak is created and they're uniformly distributed across the object heap. Now suppose the application needs to create an object that's too big to fit in any of the available gaps in the object heap. Under these circumstances, the application would come to a grinding halt and the only thing the user could do is quit and restart the application (if the computer doesn't crash).

DETECTING ACCESS FAULTS

Discovering access faults is easy. The Power Mac Debugger loudly, almost proudly, proclaims, "Access Fault." If luck is with you, your machine doesn't crash or lock up. Identifying the cause of an access fault is another matter. If the access fault involves a TObject-based object, that means the application attempted to access an object that doesn't exist. There are two ways that can happen: Perhaps the object was created, then destroyed, and now the application attempts to access it. Or maybe it was never created in the first place.

Object display can help you identify the offending object by providing an ordered record of what was created and what was destroyed. If you've been testing with object display on, you will have become familiar with what your application is doing. Then the trick is to single step up to the point of the access fault without failing. At that point, you should know which object the application is attempting to access. You can carefully examine the results of the object display to determine the source of the problem.

Access fault of the first kind. One type of access fault, which I'll call an access fault of the first kind, arises from creating a TObject-based object, freeing it, and then attempting to access it. Because it was freed, it no longer exists, so attempting to access it causes an access fault.

When I was first teaching myself about MacApp's scripting capability, I made the mistake of taking some MacApp code out of context and using it as a template in Twist Down Lists. It was clearly the wrong thing to do because it resulted in an access fault of the first kind. My mistake is illustrated by the following code, which I wrote in TTwistDownApp::GetContainedObject. I show it here so that you can try it and see for yourself how object display helps you find the first type of access fault.

TTwistDownDocument* theTwistDownDocument = NULL;
theTwistDownDocument = (TTwistDownDocument*)aDocument;
theTwistDownView = theTwistDownDocument->fTwistDownView;
TOSADispatcher::fgDispatcher->AddTemporaryToken(theTwistDownView);
result = theTwistDownView;
return result;
Of course, in due time, MacApp freed the temporary token and, later on when the application attempted to access fTwistDownView, an access fault was generated. Running the application with object display on clearly showed twistDownView being destroyed: you can't miss it and you know it's wrong. Then, a little bit of single stepping led me to the culprit. I recognized that I shouldn't have told fgDispatcher to add fTwistDownView as a temporary token. I fixed this by deleting the statement that tells fgDispatcher to add it, and then carried on.

Access fault of the second kind. Another kind of access fault, which I'll call an access fault of the second kind, arises from attempting to access a TObject-based object that was never created. The only access fault of this kind that I've encountered arose when I ran a script that asked the application to access a document when there were no documents. In this case, TApplication::GetContainedObject doesn't verify that the document exists before attempting to use it.

For this situation, the problem was immediately obvious. It was easily fixed by inserting into TTwistDownApp::GetContainedObject the code shown in Listing 2, which makes sure the document exists before attempting to access it.


Listing 2. A solution to the GetContainedObject problem

...
else if (desiredType == cDocument && selectionForm == formName) {
   CStr255   theName;
   selectionData.GetString(theName);
   CNoGhostDocsIterator iter(this);

  
   for (TDocument* aDocument = iter.FirstDocument(); iter.More();
         aDocument = iter.NextDocument()) {
      if (aDocument != NULL) {
         CStr255 name = gEmptyString;
         aDocument->GetTitle(name);
         if (name == theName) {
            theTwistDownDocument = (TTwistDownDocument*)aDocument;
            result = theTwistDownDocument;
            return result;
         }
      }
   }
}

This case demonstrates the wisdom of trying to break your application by attempting to get it to do outlandish things that no sane person would try. That's precisely how I stumbled on this one.

Access fault of the third kind. All other access faults I've defined as access faults of the third kind: they are, strictly speaking, outside the scope of MacApp. They arise from mistakes you made when working with the system software -- for example, failing to clear a parameter block before using it. As a result, object display isn't quite as helpful at tracking down these access faults as it is with finding access faults involving TObject-based objects. If you're lucky, object display will point you in the general area of the problem.

The MacApp application IconEdit gives us an example. Along with the other files that accompany this article, I've provided a test script, a modified version of the IconEdit source code, and many IconEdit documents to help you conduct the following experiment:

  1. Set the partition size of IconEdit to its minimum of 1506.

  2. Make and save about 25 IconEdit documents.

  3. Quit IconEdit to quickly get rid of all the open documents.

  4. Make a script that tells IconEdit to open all the saved documents.

  5. Run the script.
When IconEdit runs out of memory while being driven by the script, it will generate an access fault of the third kind and drop into MacsBug with a bus error. This should occur after the 22nd document has been opened and the script is telling IconEdit to open the 24th saved document. The 23rd document has failed to open for lack of memory, and the application is attempting to recover, yet the script has gone beyond that point and is telling the application to open the 24th document. (Note that you'd need to use a lot more documents to duplicate this condition if you didn't compile with the substitute PlatformMemory files, which implement object heap discipline, as described later.)

The problem occurs when the application attempts to return an out-of-memory message to the script. Specifically, TAppleEvent::WriteLong generates another error when it attempts to complete the reply Apple event that's supposed to tell the script about the out-of-memory condition.

This is a case where the techniques described in this article don't help you very much and may actually hinder you. I didn't do anything wrong, but I did spend time proving that I didn't do anything wrong. Once I got assurance that all the TObject-descended objects in my application appeared to be OK, I decided to see if IconEdit had the same problem. It did.

In due time, I noticed that the TServerCommand constructor sets fSuspendTheEvent to FALSE. TServerCommand is an ancestor of TODocCommand, which is responsible for opening existing documents. At that point, I had nothing to lose by setting its value to TRUE. That fixed the problem.

    Be warned that the experts will tell you that fSuspendTheEvent should never be set to TRUE because doing so can be dangerous. I've disregarded their advice with no better rationale than that it appears to allow IconEdit and Twist Down Lists to survive without crashing when I run a script that sends open document commands until the application fails for lack of memory. As of this writing I haven't found a more acceptable workaround.*

IMPLEMENTING OBJECT DISPLAY

To implement object display, you can plug in the substitute UObject.h and UObject.cp files. (Implementation details are provided in "EN1 - Object Counting and Display.") In addition, four new methods need to be added to TObject:
#if qDebug
void TObject::PrintConstructorClassInfo();
void TObject::PrintDestructorClassInfo();
void TObject::PrintAppConstructorClassInfo();
void TObject::PrintAppDestructorClassInfo();
#endif
The constructors and destructors of all objects for which you want to be able to display object information must be modified to call the appropriate method. For MacApp objects, use the following code in the constructor:
#if qDebug
this->PrintConstructorClassInfo();
#endif
and this code in the destructor:
#if qDebug
this->PrintDestructorClassInfo();
#endif
You may not want to call these methods in TEvent and TToolboxEvent. The Macintosh specializes in generating events, so displaying object information for them can be overwhelming. In your application objects, use the following code in the constructor:
#if qDebug
this->PrintAppConstructorClassInfo();
#endif
and this code in the destructor:
#if qDebug
this->PrintAppDestructorClassInfo();
#endif
These calls should always be placed in the same relative position in constructors and destructors. The very beginning or the very end are the two most obvious choices. Keep in mind that although constructors don't generally make other objects, destructors frequently free other objects. If these methods are invoked at random places in the constructors and destructors, the resulting object information displayed in the log window will be very hard to interpret.

There are three flags that you can use to control the amount of object information that's displayed: gPrintBaseClassInfo, gPrintMacAppClassInfo, and gPrintAppClassInfo. These flags determine whether object information is displayed at the TObject level, for MacApp objects, or for your application's objects, respectively. All three flags can be set with scriptable menu commands. However, it's probably best to set gPrintBaseClassInfo programmatically to avoid being inundated with object information for every TToolboxEvent that's generated. Simply surround the suspect code as follows:

gPrintBaseClassInfo = TRUE;
...   // suspect code here
gPrintBaseClassInfo = FALSE;
In my experience, it's usually enough to display object information at the application level and the MacApp level. However, some MacApp objects don't have constructors and some don't have destructors. If you suspect that those objects are the source of a problem, it may be useful to display object information at the TObject level.


OBJECT HEAP DISCIPLINE

MacApp uses its own object heap to store TObject-derived objects. The heap grows as new objects are created -- by taking memory from free memory. Once memory has been allocated to the object heap, it's never returned to free memory. As things stand, the developer has little control over this situation. According to conventional wisdom, the point of greatest memory usage occurs during printing. With Twist Down Lists, memory usage problems occur when the application runs out of memory while loading a hierarchical list, especially with 680x0 versions. That meant I had two problems to deal with while testing recovery from an out-of-memory condition when loading a list: the recovery itself and the lack of available memory in which to load required code segments. I made the segment loading problem go away by implementing object heap discipline, which let me concentrate on testing failure recovery. Object heap discipline allows you to erect a barrier to further expansion of the object heap right where you want it. At the same time, it allows you to leave as much memory as is required to load code segments without having to fuss with 'seg!' and 'res!' resources.

When the object heap runs out of space, a request for a new block of memory is made with a call to the global function PlatformAllocateBlock(size_t size). The trick is to force PlatformAllocateBlock to reject the request when you want it to.

To do that, I created the global down-counter gOHRemainingIncrements to maintain a count of the number of times the object heap will be allowed to expand. Each time PlatformAllocateBlock allocates memory to the object heap, it decrements gOHRemainingIncrements. When gOHRemainingIncrements reaches 0, PlatformAllocateBlock will no longer honor requests for additional memory. The revised version of PlatformAllocateBlock is shown in Listing 3.


Listing 3. Revised PlatformAllocateBlock

void *PlatformAllocateBlock(size_t size)
{
   Boolean   heapPerm;

   if (gUMemoryInitialized)
      heapPerm = PermAllocation(TRUE);
   
   void *ptr = NULL;                    // added
   // void *ptr = NewPtr(size);         // commented out
   if (gOHRemainingIncrements > 0) { // added
      ptr = NewPtr(size);               // added
      gOHRemainingIncrements--;         // added
   }                                    // added

   if (gUMemoryInitialized)
      PermAllocation(heapPerm);         // Reset perm flag before 
                                        // possible Failure
   FailNIL(ptr);

   return ptr;
}

The initial value of gOHRemainingIncrements is set to 3 just to be safe. During initialization, MacApp makes two allocations to the object heap; if gOHRemainingIncrements is 0, the application doesn't start up because of lack of memory. The second of those allocations sets up the initial size of the object heap. If your 'mem!' resource specifies a small value for the initial size of the object heap, the initial value of gOHRemainingIncrements might have to be larger than 3.

Immediately following the call to InitUMacApp in main, the value of gOHRemainingIncrements is set with a call to the InitMaxObjectHeapSize global function, which is shown in Listing 4.

gOHRemainingIncrements = InitMaxObjectHeapSize();


Listing 4. Determining the number of times the object heap will be allowed to expand

short InitMaxObjectHeapSize()
{
   long   freeMem = FreeMem();
   Size   heapSizeIncrement = gSizeHeapIncrement;
   short   theNumber = 0;

   if (freeMem > kFreeMemReserve)
      theNumber = (freeMem - kFreeMemReserve)/heapSizeIncrement;
   if (theNumber >= 1)
      theNumber = theNumber -1;
   else
      theNumber = 0;

   return theNumber;    // The number of times we'll let the object
                        // heap be expanded
}

As you can see, I use a very simple algorithm to determine the number of times the object heap will be allowed to expand and still leave in free memory at least the number of bytes specified by kFreeMemReserve.

The changes you need to make to MacApp to implement object heap discipline are described in detail in "EN2 - Object Heap Discipline." The substitute PlatformMemory.h and PlatformMemory.cp files are also provided.


FAILURE HANDLING

One very good reason to use MacApp is its integrated failure handling scheme. Of course, all failure recovery paths must be tested. In a well-crafted application, failures should occur only while the application is attempting to create a new object when there's insufficient space in the object heap for it. To test these situations, the application must be forced to fail at selected points. It's not enough to adjust the partition size and hope for a failure.

Ideally, you would be able to set a failure point with a debugger in a similar manner to setting a breakpoint. That's not presently possible. Instead, in Twist Down Lists, I added a global flag gFailHere, which is set and cleared with a scriptable menu command. There are several ways to use this flag:

  • Insert the following code at an appropriate place in the application (this is the simplest way):
    if (gFailHere)
       Failure(errFailHere, 0);

  • Force a failure just after a new object has been created:

    TSomeObject* someObject = new TSomeObject;
    FailNIL(someObject);
    someObject->ISomeObject();
    if (gFailHere)
       Failure(errFailHere, 0);

  • Force the failure in ISomeObject:

    TSomeObject::ISomeObject()
    {
       this->IObject();
       if (gFailHere)
          Failure(errFailHere, 0);
    }

Other ways of using this technique to force a failure require application-specific knowledge. In the case of Twist Down Lists, it's often convenient to give the name FailHere to a file or folder on the volume you're going to open. With the following code, when a twistDownElement named FailHere is encountered, the failure will be triggered:

if (gFailHere) {
   CStr63 failHereText = "FailHere";
   CStr63 displayedText = gEmptyString;
   twistDownElement->GetDisplayedText(displayedText);
   if (failHereText == displayedText)
      Failure(errFailHere, 0);
}
It must be possible to set and clear the gFailHere flag from a script. An application can encounter the same failure conditions whether driven from a script or from the user interface. The failure recovery path is, however, a little different. When the application is being driven by a script, an Apple event must be sent to the script telling it that a failure was encountered and what the failure was. MacApp will handle the overhead, but you must do your part: you must test it to make sure it works and returns appropriate error information to the script.

Were it not for the fact that all the list processing methods in TTwistDownDocument are recursive, I probably wouldn't have felt the need to implement gFailHere. Failure can occur if the application attempts to make a twistDownElement or a twistDownControl when there isn't enough memory in the object heap to do it and the object heap can't be further expanded. The failure might occur several levels into the recursion. You can't call ReSignal to handle the failure because you'll jump all the way up to the method that started the recursion. Instead, you must save the failure information, work your way back up the recursion, and then signal the failure.

Using gFailHere turned out to be the best way to test the failure handling. Object counting, memory display, and object display were very useful in testing recovery from these kinds of failures. Object counting and memory display verified that everything that needed to be freed was freed. Using object display to match constructions with destructions gave further confirmation that the recovery was successful.


HAPPY DEBUGGING

The debugging aids I developed illustrate the power of MacApp. By modifying the central organizing object, TObject, you can make many new capabilities, such as object counting, memory display, and object display, extend to the objects that inherit from it. In addition, you can easily modify the memory management scheme of MacApp, so implementing object heap discipline isn't hard at all. Now that I have these debugging aids, I no longer fear the dreaded memory leak and access fault. Object counting, memory display, and object display don't exactly sound an alarm when there's a TObject-based memory leak, but they come pretty close. And without object display, finding an access fault was like looking for a needle in a haystack.

The faster you can fix your mistakes, the faster you can finish your applications. I hope my debugging aids will help you get those applications out even quicker.


    RELATED READING

    • Programmer's Guide to MacApp (Apple Computer, Inc., 1996). Available on the Web at http://www.devtools.apple.com/macapp.

    • "Displaying Hierarchical Lists" by Martin Minow, develop Issue 18, and "An Object-Oriented Approach to Hierarchical Lists" by Jan Bruyndonckx, develop Issue 21.

    • "A Reassuring Progress Indicator for MacApp" by James Plamondon, FrameWorks Volume 5, Number 3, June 1991, page 46.


CONRAD KOPALA (ckopala@aol.com) believes you should never trust a computer you can't program. He's been a student of MacApp for the last six years and just recently thinks he might know a smidgen about it. In the past, Conrad was an electrical engineering professor and held positions with IBM and MCI. Now he does whatever he wants.*

Thanks to our technical reviewers Tom Becker, Geoff Clapp, Mike Rossetti, Merwyn Welcome, and Jason Yeo.*

 

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Astropad Mini 1.0 Device: iOS iPhone Category: Productivity Price: $4.99, Version: 1.0 (iTunes) Description: *** 50% off introductory price! ​*** Get the high-end experience of a Wacom tablet at a fraction of the price with Astropad... | Read more »
Emo Chorus (Music)
Emo Chorus 1.0.0 Device: iOS Universal Category: Music Price: $1.99, Version: 1.0.0 (iTunes) Description: Realistic Choir simulator ranging from simple Chorus emulation to full ensemble Choir with 128 members. ### introductory offer... | Read more »
Forest Spirit (Games)
Forest Spirit 1.0.5 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.5 (iTunes) Description: | Read more »
Ski Safari 2 (Games)
Ski Safari 2 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: The world's most fantastical, fun, family-friendly skiing game is back and better than ever! Play as Sven's sister Evana, share... | Read more »
Lara Croft GO (Games)
Lara Croft GO 1.0.47768 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.47768 (iTunes) Description: Lara Croft GO is a turn based puzzle-adventure set in a long-forgotten world. Explore the ruins of an ancient... | Read more »
Whispering Willows (Games)
Whispering Willows 1.23 Device: iOS Universal Category: Games Price: $4.99, Version: 1.23 (iTunes) Description: **LAUNCH SALE 50% OFF** - Whispering Willows is on sale for 50% off ($4.99) until September 9th. | Read more »
Calvino Noir (Games)
Calvino Noir 1.1 Device: iOS iPhone Category: Games Price: $3.99, Version: 1.1 (iTunes) Description: The film noir stealth game. Calvino Noir is the exploratory, sneaking adventure through the 1930s European criminal underworld.... | Read more »
Angel Sword (Games)
Angel Sword 1.0 Device: iOS Universal Category: Games Price: $6.99, Version: 1.0 (iTunes) Description: Prepare to adventure in the most epic full scale multiplayer 3D RPG for mobile! Experience amazing detailed graphics in full HD.... | Read more »

Price Scanner via MacPrices.net

iPad Air 2 on sale for up to $100 off MSRP
Best Buy has iPad Air 2s on sale for up to $100 off MSRP on their online store for a limited time. Choose free shipping or free local store pickup (if available). Sale prices available for online... Read more
MacBook Airs on sale for $100 off MSRP
Best Buy has MacBook Airs on sale for $100 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-store prices may vary... Read more
Big Grips Lift Handle For iPad Air and iPad A...
KEM Ventures, Inc. which pioneered the extra-large, super-protective iPad case market with the introduction of Big Grips Frame and Stand in 2011, is launching Big Grips Lift featuring a new super-... Read more
Samsung Launches Galaxy Tab S2, Its Most Powe...
Samsung Electronics America, Inc. has announced the U.S. release of the Galaxy Tab S2, its thinnest, lightest, ultra-fast tablet. Blending form and function, elegant design and multitasking power,... Read more
Tablet Screen Sizes Expanding as iPad Pro App...
Larger screen sizes are gaining favor as the tablet transforms into a productivity device, with shipments growing 185 percent year-over-year in 2015. According to a new Strategy Analytics’ Tablet... Read more
Today Only: Save US$50 on Adobe Elements 13;...
Keep the memories. lose the distractions. Summer’s winding down and it’s time to turn almost perfect shots into picture perfect memories with Elements 13. And get the power to edit both photos and... Read more
1.4GHz Mac mini on sale for $449, save $50
Best Buy has the 1.4GHz Mac mini on sale for $50 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Price for online orders only, in-store price may vary... Read more
12-inch 1.1GHz Gold MacBook on sale for $1149...
B&H Photo has the 12″ 1.1GHz Gold Retina MacBook on sale for $1149.99 including free shipping plus NY sales tax only. Their price is $150 off MSRP, and it’s the lowest price available for this... Read more
27-inch 3.3GHz 5K iMac on sale for $1849, sav...
Best Buy has the 27″ 3.3GHz 5K iMac on sale for $1849.99. Their price is $150 off MSRP, and it’s the lowest price available for this model. Choose free shipping or free local store pickup (if... Read more
Worldwide Tablet Shipments Expected to Declin...
Does Apple badly need a touchscreen convertible/hybrid laptop MacBook? Yes, judging from a new market forecast from the International Data Corporation (IDC) Worldwide Quarterly Tablet Tracker, which... Read more

Jobs Board

*Apple* Retail Online Store: Customer Insigh...
**Job Summary** Apple Retail (Online Store) is seeking an experienced e-commerce analytics professional to join the Customer Insights Team. The Web e-Commerce Analyst Read more
*Apple* Music, Business Operations - Apple I...
Changing the world is all in a day039s work at Apple . If you love innovation, here039s your chance to make a career of it. You039ll work hard. But the job comes with Read more
WW *Apple* Retail Online Store: Customer In...
**Job Summary** The Apple Retail - Online Store is seeking an experienced web merchandising analytics professional to join the Customer Insights Team. The Web Read more
Senior Payments Security Manager - *Apple*...
**Job Summary** Apple , Inc. is looking for a highly motivated, innovative and hands-on senior payments security manager to join the Apple Pay security team. You will Read more
Software QA Engineer, *Apple* Pay Security...
**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
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