TweetFollow Us on Twitter

Jan 94 Top 10
Volume Number:10
Issue Number:1
Column Tag:Think Top 10

Think Top 10

By Kevin Irlen, Think Technical Support, Symantec Corp.

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

This is a monthly column written by Symantec’s Technical Support Engineers intended to provide you with information on Symantec products. Each month we cover either a specific application of tools or a “Q&A” list.

Q. I’m trying to compile a simple “Hello World” example in C++, and I get an “invalid declaration” on a line that reads “class ostream;” in file <2comp.h>. What’s going on, and where did this file come from?

A. You’ve #includ’ed <iostream.h>, but by reflex, you must have created a .c file... Since the default translator for .c files is the C translator, <iostream.h> just ain’t gonna compile. The first place it violates C syntax is in the indicated line in <2comp.h> which <iostream.h> #include’s. Until you realize what’s going on here, this can be pretty confusing! Save your file as a .cp file, and this problem should disappear.

Q. How do I send my output to the printer using IOStreams? And I just want specific output to go to the printer, not my users’ prompts and responses.

A. IOStreams works on top of the Standard Library console package, so cin is tied to stdin, cout to stdout, and cerr to stderr. To echo stdout to a file or to the printer, you still use cecho2file or cecho2printer. With the Standard Library console package, separating output from the main console means simply creating another console, using fopenc. The strategy is the same for IOStreams, the only trick is tying the new console to a stream. This is done via a stdiobuf, as illustrated below:

/* 1 */
#include <console.h>
#include <fstream.h>
#include <stdiostr.h>

void main(void)
{
 FILE    *fp = fopenc();
 stdiobuf fps(fp);
 ostream  os (&fps);
 
 chide        (fp);
 cecho2printer(fp); 

 os   << "This goes to hidden console & the printer" << endl;
 cout << "This goes to the user."                    << endl;
}

Q. I’m trying to override the global operator new. But I get “multiply defined: operator new(unsigned int) (myfile.cp, CPlusLib)”. What should I do?

A. There is really no such thing as “overriding” global operator new. You can overload it by supplying a function which takes additional arguments beyond the required size_t first argument, and you can provide a class with its own operator new; but if you want to replace the global operator new(size_t) that is defined in CPlusLib, then you’ll have to do just that -- replace it, and have your own custom CPlusLib. (In other words, as far as the linker is concerned, operator new is treated just like any other function.)

One interesting example of overloading global operator new is the “placement” operator new provided by <stddef.h>, which takes an additional void * argument and simply returns that same argument. The purpose of this function is to allow previously allocated storage to be used to hold a new instance of an object, while retaining the constructor-calling action of operator new. (Here again, if for some reason you wanted to “override” this function you would have to replace it.)

Finally, the confusion about “overriding” may come from the fact that you can override the “new handler” which is called when a memory allocation request can’t be met. This is done simply by calling set_new_handler with a pointer to your “new handler” function.

Q. I have an abstract class with all pure virtual functions, including the destructor. I do not define any of these functions, since they must be overridden in a derived class. However, a get a link error telling me the abstract class’ destructor is undefined. What’s going on?

A. Virtual destructors insure that the appropriate destructor gets called first for an object whose class is not determined until run time.

/* 2 */

class A
{
 virtual ~A();
 ... 
};

class B : A 
{
 ~B();
 ... 
};

void main(void)
{
 A *a;
  ...
 a = new B;
  ...
 delete a;   // B's destructor called first.
  ...
}

They do not change the fact that destructors are then called for each base class when the derived class object is being destructed. Declaring a destructor pure virtual does not change this fact either. The pure specifier here, as with any function, forces the class to be abstract, and forces the derived class to define a destructor of the same type; but unlike with “regular” functions, it does not, and cannot bypass the need for the abstract class’ destructor actually to be able to called.

Q. All I did was add IOStreams to Starter++.Π and I’m crashing before I get to through application initialization.

A. IOStreams allocates memory during static initialization. The default 200K partition used by the Starter project will no longer be sufficient. Increase it to 300K, and the problem should disappear.

Q. Do libraries’ “Set Project Type” settings have to match the project’s “Set Project Type” settings exactly? Especially, what about Far Code and Far Data?

A. OK, here’s the whole deal...

Project Type: If the main project is an application, libraries must be applications as well. This is because globals and jumps are going to be referenced off of A5.

If the main project is not an application, libraries must be code resources. This is because globals and jumps are going to be referenced off of A4.

Partition: Libraries’ settings are ignored.

Size Flags: Libraries’ settings are ignored.

Separate STRS: If turned on in a library, the main project must be built with this option on as well.

(Separate STRS has no effect in C++.)

Far Code and Far Data: Some libraries explicitly test for these options, and compile differently based on their being on or off. Obviously, you would need to use the proper version of such libraries. The only THINK libraries that do this are oops and oopsDebug (and oops++ and oopsDebug++), and we provide oopsFar and oopsDebugFar pre-built (ditto for the ++ ones). For libraries that do not compile differently under different FAR or NEAR options, there is usually no need to build FAR versions of them in order to use them in a FAR project. However, as explained on pp.266-7 of the THINK User’s Guide, you should segregate NEAR libraries from the rest of your code. Finally, there are two cases where even segregating your NEAR libraries is not sufficient, and one or more of your libraries will have to be changed to FAR.

1) THINK must put all jump table entries of a NEAR CODE library into the first 32K of the jump table. Furthermore, if your NEAR CODE library calls out to a function in the main project (or in another library), then that function’s jump table entry must also be within the first 32K of the jump table. To provide a mechanism for this, THINK will create NEAR jump table entries for ALL functions in a segment containing a NEAR CODE library. Thus, a problem arises if your combined NEAR CODE libraries require more than 32K of jump table, or if, by putting other source files in the same segment as a NEAR CODE library, you cause the first 32K of the jump table to be used up before all the libraries’ NEAR entries can be placed: THINK will be unable to create enough NEAR jump table entries and you’ll get ILLEGAL NEAR REFERENCE link errors.

2) Similarly, THINK must put all global data referenced by a NEAR DATA library into the first 32K of the application’s global variable space. If a NEAR DATA library references external global data, then the file where the external data is defined must be in the same segment as a NEAR DATA library so its globals will also be stored in NEAR global variable space. Thus, a problem arises if the combined data of your NEAR libraries is greater than 32K, or if by putting other source files in the same segment as a NEAR DATA library you cause the first 32K of the application’s global variable space to be used up before all the libraries’ NEAR data can be placed: THINK will be unable to place all the NEAR DATA properly, and you’ll get ILLEGAL NEAR REFERENCE link errors.

In C++, all class vtables occupy global data space, so the FAR project/NEAR library problem can crop up if the library refers to classes that it does not define.

Q. We’re using SourceServer, and want to store our .rsrc files in the ProjectorDB along with our source files. As usual, SourceServer adds a ‘ckid’ 128 resource to each file, so we were worried that when we added the .rsrc files to a project we would get ‘duplicate resource’ errors when we tried to compile. But we don’t. Why?

A. If you take a look at the Resource Copier translator in ResEdit, you’ll notice that it’s got a ‘SKIP’ resource. This resource contains a list of resource types, which, as its name suggests, are to be skipped during resource copying. By default, it contains a single entry, ‘ckid’. (Yes, this means you could add other resources to the SKIP list; though I can’t think of a reason why you’d ever want to...)

Q. I’m running out of memory when running and debugging my C++ programs. Until I have more RAM, is there anything I can do to use the memory I have more efficiently?

A. First of all, make sure you understand what your memory situation looks like before compiling, and what it should look like once you’re successfully up and running under the debugger. For example, on a Mac LC III with 4Mb RAM things might look like this:

Before compiling:

System Software 1,100K

THINK Project Manager 2,048K

Free Memory 852K

After compiling, and running w/the debugger:

System Software 1,100K

THINK Project Manager 2,048K

Debugger 250K

Application 500K

Free Memory 102K

When memory is tight, you’ll have to strike a balance among these five pieces. Clearly you want your System to be as lean as possible. Keep in mind that during compilation the THINK Project Manager attempts to make the most out of your Mac’s memory, and the most efficient use of its own partition, by allocating out of the “MultiFinder temporary pool”, or free memory. Note that in the above example the TPM’s partition has been reduced from the 4Mb default to 2Mb, leaving about 100K free. This will produce better results than giving everything available to the TPM.

If you’re running out of memory while debugging, the solution is NOT to increase the Debugger’s partition. Even though you’re in the Debugger, it’s still the compiler that’s doing the work of evaluating expressions. Again, look to the TPM/free memory combination.

If you’re running out of memory before even getting into the Debugger, try holding down the option key while choosing Run. This resets the Debugger by clearing all expressions and breakpoints. Also, double-check that the partition you’ve set for your application isn’t greater than the amount of free memory!

Finally, here are two space/time tradeoffs that can help:

1) Don’t use precompiled headers. They improve compile time, but take up valuable space in the TPM’s heap.

2) By default, both the THINK C and Symantec C++ translators are kept in memory while the TPM is running. You can allow one or both to be swapped out, and save some space at the expense of speed, by tweaking a bit in ResEdit. Open the translator in ResEdit, and then open the ‘INFO’ resource. Scroll to the bottom and switch the “Memory Resident

Q. I want to write some assembly language for my C++ project, but I can’t! The C++ compiler doesn't have an inline assembler and I can't figure out how to call my C++ functions from THINK C. Is there no hope?

A. You can call a C++ function from within an inline assembler block in the same way you would a C function: just JSR to the function. There is a slight complication though: the C++ language implements its type-safe linkage by “mangling” the name of functions and methods to contain the type information. So to call a C++ function from C, you need to use its mangled name. You can get the mangled name by turning on the “Generate MacsBug names” option in the Symantec C++ options dialog and disassembling the file containing the function whose mangled name you want. The mangled name will appear in a string at the end of the function. For example, assume that foo.cp contains the function:

Translator” from 1 to 0.

Q. I’ve got the .o extension mapped to the .o Converter. Why doesn’t my .o file appear in the Add Files... list?

A. In addition to having an extension for which there’s a translator, translators will only accept certain file types. A .o file must be of type ‘OBJ ’. If your .o file has “been around” (e.g. you downloaded it from an online service) it may have lost the ‘OBJ ’.

Q. I’m using your “Save Project as Text” and “Create Project From Text” scripts. They work fine except for one small problem: they don’t restore my project’s settings.

A. This is indeed a shortcoming of these scripts. Unfortunately, the data structures which hold the project settings don’t lend themselves easily to the “Save as Text” approach. Here’s a straightforward script to run after running “Create Project from Text” which allows you to copy the project settings from the original project to the new one. Not quite as nice as actually saving the settings as text along with the rest of the project, but it will fill the gap in many situations:

!coddexamplestart
/* 3 */
copy "Hard Drive:Proj Folder:newProj.Π" to targetProjName

tell application "THINK Project Manager"
 tell project document 1
 copy project type to projType

 copy options block 1 to options1
 copy options block 2 to options2
 copy options block 3 to options3
 copy options block 4 to options4
 copy options block 5 to options5
 
 close
 end tell
 
 open file targetProjName
 
 tell project document 1
 set project type to projType

 set options block 1 to options1
 set options block 2 to options2
 set options block 3 to options3
 set options block 4 to options4
 set options block 5 to options5
 end tell
end tell
!coddexampleend

 
AAPL
$111.16
Apple Inc.
+1.75
MSFT
$47.05
Microsoft Corpora
+1.31
GOOG
$510.51
Google Inc.
+5.62

MacTech Search:
Community Search:

Software Updates via MacUpdate

BBEdit 11.0.2 - Powerful text and HTML e...
BBEdit is the leading professional HTML and text editor for the Mac. Specifically crafted in response to the needs of Web authors and software developers, this award-winning product provides a... Read more
ExpanDrive 4.2.1 - Access cloud storage...
ExpanDrive builds cloud storage in every application, acts just like a USB drive plugged into your Mac. With ExpanDrive, you can securely access any remote file server directly from the Finder or... Read more
Adobe After Effects CC 2014 13.2 - Creat...
After Effects CC 2014 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous After Effects customer). After Effects CS6 is still available... Read more
Command-C 1.1.7 - Clipboard sharing tool...
Command-C is a revolutionary app which makes easy to share your clipboard between iOS and OS X using your local WiFi network, even if the app is not currently opened. Copy anything (text, pictures,... Read more
Tidy Up 4.0.2 - Find duplicate files and...
Tidy Up is a complete duplicate finder and disk-tidiness utility. With Tidy Up you can search for duplicate files and packages by the owner application, content, type, creator, extension, time... Read more
Typinator 6.3 - 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
GraphicConverter 9.5 - Graphics editor w...
GraphicConverter is an all-purpose image-editing program that can import 200 different graphic-based formats, edit the image, and export it to any of 80 available file formats. The high-end editing... Read more
Toast Titanium 12.0.1 - The ultimate med...
Toast Titanium goes way beyond the very basic burning in the Mac OS and iLife software, and sets the standard for burning CDs, DVDs, and now Blu-ray discs on the Mac. Create superior sounding audio... Read more
QuickBooks 2015 16.0.2.1422 R3 - Financi...
Save 20% on QuickBooks Pro for Mac today through this special discount link QuickBooks Pro 2013 helps you manage your business easily and efficiently. Organize your finances all in one place, track... Read more
Remotix 3.0.6 - Access all your computer...
Remotix is a fast and powerful application to easily access multiple Macs (and PCs) from your own Mac. Features: Complete Apple Screen Sharing support - including Mac OS X login, clipboard... Read more

Latest Forum Discussions

See All

Brothers in Arms 3: Sons of War Review
Brothers in Arms 3: Sons of War Review By Jennifer Allen on December 18th, 2014 Our Rating: :: FUN BUT PUSHYUniversal App - Designed for iPhone and iPad Brothers in Arms 3: Sons of War could be great fun, but its plethora of... | Read more »
The Snow is Falling on the French Countr...
The Snow is Falling on the French Countryside of Carcassonne’s Newest Update Posted by Jessica Fisher on December 18th, 2014 [ permalink ] < | Read more »
Creatures Such As We Review
Creatures Such As We Review By Jennifer Allen on December 18th, 2014 Our Rating: :: INTERESTING DISCUSSIONSUniversal App - Designed for iPhone and iPad Taking a more sedate approach to interactive fiction, Creatures Such As We... | Read more »
Give It Up! (Games)
Give It Up! 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: GIVE IT UP is a rather hard game where you have to assist this cheerful, singing Blob in jumping through 9 different tracks.So far... | Read more »
The Drive : Devil's Run (Games)
The Drive : Devil's Run 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: ON THE ROAD AGAIN! The Drive - Devil’s Run is classic point to point style racing game that pays homage to the classics... | Read more »
Procreate Pocket (Entertainment)
Procreate Pocket 1.01 Device: iOS iPhone Category: Entertainment Price: $2.99, Version: 1.01 (iTunes) Description: Create - anytime, anywhere. Made by the developers of the award-winning Procreate® for iPad®, Procreate Pocket™ allows... | Read more »
IRON FINGER - Mini Games Championship (...
IRON FINGER - Mini Games Championship 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Quick to play, easy to learn yet hard to master.. TAP, SWIPE & TILT your way through mini games that... | Read more »
Pentaction: Medieval (Games)
Pentaction: Medieval 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Pentaction: Medieval is a turn-based strategy board-game about chance and skill on the battlefield. Take control of your... | Read more »
Hipstify Review
Hipstify Review By Jennifer Allen on December 17th, 2014 Our Rating: :: COOL FILTERSUniversal App - Designed for iPhone and iPad Add filters, quotes, and fancy frames to your images, thanks to Hipstify.   | Read more »
Mighty Smighties Gets Evolve Cards and N...
Mighty Smighties Gets Evolve Cards and New Worlds Posted by Jessica Fisher on December 17th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »

Price Scanner via MacPrices.net

KMI MIDI K-Board Great Gift for Amateur &...
The K-Board is a MIDI Nano keyboard for music creation for iPad, Android, And computers; the easiest way to make music with iPads & Android tablets, and Mac, Windows, or Linux computers. Ultra-... Read more
Amazon offers 15-inch 2.2GHz Retina MacBook P...
 Amazon.com has the 15″ 2.2GHz Retina MacBook Pro on sale for $1699 including free shipping. Their price is $300 off MSRP. Stock is limited, so act now if you’re interested. Read more
Holiday sales continue: MacBook Pros for up t...
 B&H Photo has new MacBook Pros on sale for up to $300 off MSRP as part of their Holiday pricing. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.2GHz Retina MacBook Pro: $1699... Read more
Google Search App For iOS Gets A Major Makeov...
Google has given iOS users an early Christmas present with a substantial update of it’s not-very-often-upgraded Google Search app. Google Search has been my go-to tool for Web searches since it was... Read more
ShopKeep Apple Pay And Chip Card Reader Avail...
ShopKeep, a cloud-based technology provider to more than 10,000 small business owners to manage retail shops and restaurants with iPads, has released its new Apple Pay and chip card reader. This... Read more
Holiday sale! 27-inch 5K iMac for $2299, save...
 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
Holiday Sale! 3.7GHz Quad Core Mac Pro availa...
 B&H Photo has the 3.7GHz Quad Core Mac Pro on sale for $2599 including free shipping plus NY sales tax only. Their price is $400 off MSRP, and it’s the lowest price for this model from any... Read more
iPhone 6 Number 3 Canadian Google Search Of 2...
CTVNews.ca reports that Apple’s iPhone 6 was the third highest-trending Google Canada search topic of 2014, exceeded only by Robin Williams largely after his death by suicide in August, and the FIFA... Read more
New iPad mini 3 Counter-Top & Wall Mount...
newMacgadgets has announced new secure all-acrylic displays for the iPad mini 3 (also works fine with the mini 2, last year’s iPad mini With Retina Display, and the original iPad mini). The new iPad... Read more
Holiday sales continue, MacBook Airs for up t...
B&H Photo has 2014 MacBook Airs on sale for up to $120 off MSRP, for a limited time, for the Thanksgiving/Christmas Holiday shopping season. Shipping is free, and B&H charges NY sales tax... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Project Manager / Business Analyst, WW *Appl...
…a senior project manager / business analyst to work within our Worldwide Apple Fulfillment Operations and the Business Process Re-engineering team. This role will work Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.