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Volume Number: 12
Issue Number: 2
Column Tag: Symantec Top 10
Symantec Top 10 [TOKEN:61440]
This monthly column, written by Symantec’s Technical Support
Engineers, is intended to give our readers technical information on
using Symantec products.
By Michael Hopkins, Symantec
Note: Source code files accompanying article are located on MacTech CD-ROM orsource code disks.
Q: I am compiling my project with the THINK Project Manager and I get an error
Options dialog box and not Far CODE. To turn on Far CODE, choose Set
more information on how to use Far CODE and Far DATA, consult your User’s
Guide.
Q: I have written some simple code that has a structure declaration in a header file
and then a global variable of that structure type in my main source file. When I
compile the code, I get the message "Error: Size of struct is not known.
Furthermore, when I preprocess the file, I don’t see my struct declaration
being included. What is going on?
A: Let’s take a look at an example:
/* main.c */
#include "timer.h
struct clock local_clock;
main()
{
}
/* timer.h */
struct clock {
long start_time;
long end_time;
};
What is wrong with this picture? Well, there is actually nothing wrong with the
structure. The problem is that Timer.h is the name of a system include file that
is automatically included as part of the precompiled headers (in this case,
MacHeaders). Therefore, the user header file is not being included because a
system file of the same name is being used. To correct this problem, either
rename the user header file or, for non-Macintosh applications, do not include
MacHeaders in the prefix.
Q: I am writing a virus scanning program and I need to examine code resources of an
application to verify that they are valid. What information does the Symantec
Linker place in the first two bytes of the code resource?
A: For all CODE segments besides CODE 0, there is a code segment header. The
THINK Linkers use the upper bit of this header to indicate a model Far CODE
segment. The runtime loader resides in CODE 1 of the application and is the first
piece of code executed. The loader loads and initializes the DATA and STRS,
installs hooks for _LoadSeg, _UnloadSeg, and _ExitToShell traps, and calls
the main program.
If the code is using a far model, the _LoadSeg and _UnloadSeg bottlenecks
completely replace the standard segment loader. The standard 4-byte CODE
segment header is interpreted differently to accommodate the larger jump table,
so it is incompatible with the ROM segment loader. The header has the following
format:
runtime. These are stored in a CREL resource with the same resource ID as the
header.
Be aware that this format is different from the header that MPW and Merowerks
use as well as the CFM-68K header format.
Q: I am trying to use ODBC (Open DataBase Collaboration) with the THINK Project
manager and I am getting a number of link errors. What library files to I need to
add to use ODBC?
A: To use ODBC, you will need to include:
• MacTraps and MacTraps2
• LibraryManagerClient.o
• alloc_private.c
You will also need to write two additional functions (source is in THINK
Reference under Embedded DefProc):
Boolean TrapAvailable( short theTrap );
void FlushCache( void );
If you are compiling one of the demos, you will need to write a stricmp:
pascal short _stricmp( const char *s, const char *s2)
{
return (short)strcmp(s, s2);
}
Q: I am making a 68K version of my PPC application and I’m getting a link error
with numtostring() which is in TextUtils.h. On the PPC, this routine is in
InterfaceLib.xcoff. Where is it on the 68K mac?
A: It is important to realize that the lower-case version of numtostring() is
different than NumToString() which is in MacTraps. NumToString() returns a
lower-case version with the THINK project manager, you will need to include
Apple C Glue which is in Macintosh Libraries:68K Libraries from the
Symantec C++ v8 Release 4 CD.
Q: Is there any way that I to make the Finder run Power Macintosh DebugServices
when I launch the SPM?
A: No, but you could tell SPM to launch DebugServices on startup or shutdown. To
run a script automatically when the Project Manager opens, record or write a
script using the Script Editor. Save the script in the (Scripts) folder and name
it “Startup”. Alternatively, if you want the script to run on exit from the
Project manager, name it “Shutdown”.
Q: I’ve noticed that all native applications have a note in the “Get Info” window that
says: “Memory requirements will decrease by xxxxK if virtual memory is
turned on in the Memory control panel”. Won’t using virtual memory decrease
my application performance?
A: No, not necessarily. In some cases the use of virtual memory on Power
Macintoshes can actually increase the runtime performance of your application.
When VM is not enabled on a Power PC, the application’s stack, heap, and all of
its code fragments have to be loaded into the application’s partition. With VM on,
only the stack and heap are loaded into the application’s partition. This reduces
launch time and requirements for native programs. The Virtual Memory
Manager will track your application’s code fragments and load them into the
application’s partition only when they are needed. If done correctly, this won’t
result in a noticeable performance penalty and the application will launch much
more quickly. For more information, refer to Inside Macintosh: PowerPC System
Q: How do I create a CustomTEHook on a PowerPC?
A: It is actually fairly straight-forward thanks to Apple’s Universal Headers.
Create your hook procedure with the following signature:
pascal unsigned short myTextWidthHookProc(
unsigned short textLen,
unsigned short textOffset,
void * textBufferPtr,
TEPtr pTE,
TEHandle hTE
);
TextWidthHookUPP myUPP =
NewTextWidthHookProc( myTextWidthHookProc );
TECustomHook( intTextWidthHook, &myUPP, myTE );
Q: I have noticed that there is a problem in CDialogText where cuts, copies and
pastes are not reported to the supervisor of the CDialogText. Is there an easy
way to fix this?
A: Yes, there is. Change the code for CDialogText::
DoCommand to:
void CDialogText::DoCommand( long theCommand )
{
inherited::DoCommand( theCommand );
switch( theCommand )
{
case cmdCut:
case cmdPaste:
case cmdClear:
if (editable)
BroadcastChange( dialogTextChanged, &ID );
break;
default:
break;
}
}
Q: How do I force Visual Architect to re-generate all sources including the files that
should only be generated once such as CMain and CApp?
A: Take the Source directory in your project folder and either rename it or move it
to a different location. Remove all of your existing generated VA files from your
project. When you choose Generate All from the Visual Architect, it will
create a new source folder and generate all of the files and then add them to your
project.
Special Thanks To
Levi Brown, Craig Conner, Rick Hartmann, Noah Lieberman, Andy McFarland, Scott
Morrison, Phil Shapiro, Jeff Weeks, Kevin Quah
Referenced by (2):