TweetFollow Us on Twitter

Sep 93 Think 10
Volume Number:9
Issue Number:9
Column Tag:Think Top 10

Think Top 10

By Thomas Emerson, THINK Technical Support, Symantec Corp.

This a monthly column written by Symantec's Technical Support Engineers intended to provide you with information on Symantec products. This month we cover some more commonly asked questions of Symantec’s developer technical support group.

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:

void foo()
{
 for(int i=0;i<10;i++)
 ;
}

Disassembling foo.cp yields in part the following:

00000012: 261F              MOVE.L    (A7)+,D3
00000014: 4E75              RTS
00000016: 8766 6F6F 5F5F    DC.B      $80+$07, 'foo__Fv'
          4676           
0000001E: 0000              DC.W      0  ; size of literals
00000020

The mangled name for foo() is foo__Fv. So to call it from within the inline assembler we would write:

 asm {
 jsr    foo__Fv
 addq.l #4,sp
 };

remembering to prototype the function correctly, i.e.

 extern void foo__Fv(void);

and remember to use C++ calling conventions when passing arguments to the function. See pp. 73-75 of the C++ Compiler Guide for more details.

Q. On a related note, whenever I try to use the asm() statement in C++, I'm told that the function asm has no prototype. What's going on?

A. You will get this error if you have “ANSI conformance” option turned on in the Language Settings page of the Symantec C++ for Macintosh options dialog. As it says on page 40 of the C++ Compiler Guide , the keyword asm is not recognized. Turn this off and you will be all set.

Q. Can I build a code resource using Symantec C++ that uses C++ objects?

A. Sure, you can use C++ objects in code resources, though they cannot contain virtual methods. This is because the resource loader code does not support the 32-bit offsets used to build the vtables that are used for virtual method dispatch. We would recommend deriving all of your classes from PascalObject, which will support virtual methods and is an all around better way of doing it.

Q. It appears that your IOStreams library doesn't work when I turn on 68881 code generation. I built a version of IOStreams with the C++ compiler set to generate 881 instructions, but the simplest programs still don't work. What's wrong?

A. There are two things you need to do when using IOStreams with 68881 code generation. The library itself contains both C and C++ code, so you need to turn on 881 code generation for both the THINK C and Symantec C++ compilers. You also need to build a version of ANSI++ that uses 68881 code generation, since IOStreams makes calls to ANSI++ to do the dirty work.

Q. I’m a little confused on the difference between Stream.h and iostream.h. When should I use one and not the other?

A. The short and sweet answer is that you should ignore Stream.h completely and always use iostream.h. Stream.h contains the classes for the old Streams library described in the first edition of The C++ Programming Language. The header file is part of the Symantec C++ for Macintosh distribution, but the library itself was left out (though it is part of the MPW version, called SCOldstreamsIO.o and SCOldstreamsIO881.o). Unless you are porting old C++ source code that uses Stream.h you should use iostream.h instead.

Q. Since we're talking about streams here, I've found that when I create an fstream it shows up on my disk as a blank icon, and I can't open it. Is there any way to tell the compiler that I want a THINK C text file?

A. You can use a “feature” of the standard library to set the type and creator used when creating files. This works because the IOStreams library calls upon ANSI++ to do its dirty work, like creating and opening files. The file <stdio.h> declared two external globals, _ftype and _fcreator. These are used to set the initial type and creator for a file, so settings these to 'TEXT' and 'KAHL' respectively will solve your problem. The following code snippet should give you an idea of what to do:

#include <fstream.h>
#include <stdio.h>

void main()
{
 fstream fs;

 // set the type and creator for any streams we open
 _ftype = 'TEXT';
 _fcreator = 'KAHL';

 fs.open("foo.bar");
  
}

Q. I've heard about something called ToolServer. What is it and how do I use it?

A. ToolServer is a product developed by Apple that allows you to execute most MPW tools and scripts (the major exceptions being the editor and Projector commands.) Applications communicate with ToolServer by exchanging Apple events: in effect an MPW command line is sent to ToolServer, and the results of the command sent back to the calling application. The THINK Project Manager provides ToolServer support with this mechanism: if you press Command-Enter within any THINK editing window then the current selection (or the line the cursor is on if there isn't a selection) is sent to ToolServer. The TPM looks for an alias called “ToolServer” in the Tools folder, and launches this application if ToolServer isn't running.

ToolServer is distributed by Apple on the E.T.O. series (it first appeared in released form on E.T.O. #11) and in the MPW 3.3 distribution, both of which are available through APDA.

Q. Supposedly this is the THINK Top 10, yet there are only 8 questions, counting this one. What's the deal?

A. Well, perhaps we should have called this month's column the “THINK Top 010.” [read it in octal for those of you scratching your heads. - Ed.]

Thanks to Chris Prinos, Kevin Irlen, and Phil Shapiro for their contributions to the answers this month.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Latest Forum Discussions

See All

Six fantastic ways to spend National Vid...
As if anyone needed an excuse to play games today, I am about to give you one: it is National Video Games Day. A day for us to play games, like we no doubt do every day. Let’s not look a gift horse in the mouth. Instead, feast your eyes on this... | Read more »
Old School RuneScape players turn out in...
The sheer leap in technological advancements in our lifetime has been mind-blowing. We went from Commodore 64s to VR glasses in what feels like a heartbeat, but more importantly, the internet. It can be a dark mess, but it also brought hundreds of... | Read more »
Today's Best Mobile Game Discounts...
Every day, we pick out a curated list of the best mobile discounts on the App Store and post them here. This list won't be comprehensive, but it every game on it is recommended. Feel free to check out the coverage we did on them in the links below... | Read more »
Nintendo and The Pokémon Company's...
Unless you have been living under a rock, you know that Nintendo has been locked in an epic battle with Pocketpair, creator of the obvious Pokémon rip-off Palworld. Nintendo often resorts to legal retaliation at the drop of a hat, but it seems this... | Read more »
Apple exclusive mobile games don’t make...
If you are a gamer on phones, no doubt you have been as distressed as I am on one huge sticking point: exclusivity. For years, Xbox and PlayStation have done battle, and before this was the Sega Genesis and the Nintendo NES. On console, it makes... | Read more »
Regionally exclusive events make no sens...
Last week, over on our sister site AppSpy, I babbled excitedly about the Pokémon GO Safari Days event. You can get nine Eevees with an explorer hat per day. Or, can you? Specifically, you, reader. Do you have the time or funds to possibly fly for... | Read more »
As Jon Bellamy defends his choice to can...
Back in March, Jagex announced the appointment of a new CEO, Jon Bellamy. Mr Bellamy then decided to almost immediately paint a huge target on his back by cancelling the Runescapes Pride event. This led to widespread condemnation about his perceived... | Read more »
Marvel Contest of Champions adds two mor...
When I saw the latest two Marvel Contest of Champions characters, I scoffed. Mr Knight and Silver Samurai, thought I, they are running out of good choices. Then I realised no, I was being far too cynical. This is one of the things that games do best... | Read more »
Grass is green, and water is wet: Pokémo...
It must be a day that ends in Y, because Pokémon Trading Card Game Pocket has kicked off its Zoroark Drop Event. Here you can get a promo version of another card, and look forward to the next Wonder Pick Event and the next Mass Outbreak that will be... | Read more »
Enter the Gungeon review
It took me a minute to get around to reviewing this game for a couple of very good reasons. The first is that Enter the Gungeon's style of roguelike bullet-hell action is teetering on the edge of being straight-up malicious, which made getting... | Read more »

Price Scanner via MacPrices.net

Take $150 off every Apple 11-inch M3 iPad Air
Amazon is offering a $150 discount on 11-inch M3 WiFi iPad Airs right now. Shipping is free: – 11″ 128GB M3 WiFi iPad Air: $449, $150 off – 11″ 256GB M3 WiFi iPad Air: $549, $150 off – 11″ 512GB M3... Read more
Apple iPad minis back on sale for $100 off MS...
Amazon is offering $100 discounts (up to 20% off) on Apple’s newest 2024 WiFi iPad minis, each with free shipping. These are the lowest prices available for new minis among the Apple retailers we... Read more
Apple’s 16-inch M4 Max MacBook Pros are on sa...
Amazon has 16-inch M4 Max MacBook Pros (Silver and Black colors) on sale for up to $410 off Apple’s MSRP right now. Shipping is free. Be sure to select Amazon as the seller, rather than a third-party... Read more
Red Pocket Mobile is offering a $150 rebate o...
Red Pocket Mobile has new Apple iPhone 17’s on sale for $150 off MSRP when you switch and open up a new line of service. Red Pocket Mobile is a nationwide MVNO using all the major wireless carrier... Read more
Switch to Verizon, and get any iPhone 16 for...
With yesterday’s introduction of the new iPhone 17 models, Verizon responded by running “on us” promos across much of the iPhone 16 lineup: iPhone 16 and 16 Plus show as $0/mo for 36 months with bill... Read more
Here is a summary of the new features in Appl...
Apple’s September 2025 event introduced major updates across its most popular product lines, focusing on health, performance, and design breakthroughs. The AirPods Pro 3 now feature best-in-class... Read more
Apple’s Smartphone Lineup Could Use A Touch o...
COMMENTARY – Whatever happened to the old adage, “less is more”? Apple’s smartphone lineup. — which is due for its annual refresh either this month or next (possibly at an Apple Event on September 9... Read more
Take $50 off every 11th-generation A16 WiFi i...
Amazon has Apple’s 11th-generation A16 WiFi iPads in stock on sale for $50 off MSRP right now. Shipping is free: – 11″ 11th-generation 128GB WiFi iPads: $299 $50 off MSRP – 11″ 11th-generation 256GB... Read more
Sunday Sale: 14-inch M4 MacBook Pros for up t...
Don’t pay full price! Amazon has Apple’s 14-inch M4 MacBook Pros (Silver and Black colors) on sale for up to $220 off MSRP right now. Shipping is free. Be sure to select Amazon as the seller, rather... Read more
Mac mini with M4 Pro CPU back on sale for $12...
B&H Photo has Apple’s Mac mini with the M4 Pro CPU back on sale for $1259, $140 off MSRP. B&H offers free 1-2 day shipping to most US addresses: – Mac mini M4 Pro CPU (24GB/512GB): $1259, $... Read more

Jobs Board

All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.