May 95 Top 10
|Column Tag:||Symantec Top 10
Symantec Top 10
This monthly column, written by Symantecs Technical Support Engineers, aims to provide you with technical information based on the use of Symantec products.
By Colen Garoutte-Carson, Quality Assurance & Technical Support, Symantec Corp.
Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.
Q: How do I build a fat application with Symantec C++ v8.0?
A: Weve touched on this before, and heres a more detailed look. When an application is launched on a 68K Macintosh, the operating system (OS) loads and executes a 68K CODE resource ID 1. When an application is launched on a PowerMac, the OS first looks for a cfrg resource describing a PowerPC code fragment stored in the applications data fork, and if found, prepares and executes the PowerPC code fragment. If the OS is unable to launch the application this way, it tries to loads and execute a 68K CODE resource ID 1.
A fat (fat-binary) application has both a PowerPC code fragment and 68K CODE resources, and can be launched on either platform.
To create a fat binary app, enable the option to merge an existing 680x0 application into your final application, in the project Options dialog, in the Project Type settings for an application. This copies all resources from the 68K application that do not already exist in your PowerPC application. Most importantly, this copies all 68K CODE resources to your PowerPC application.
Resources in your 68K application with the same type and ID as those in your PowerPC application will not be copied.
You can also build a fat application by including a 68K applications CODE resources in a resource (.rsrc) file, and adding that resource file to your PowerPC project.
Q: How do I create an accelerated code resource?
A: Although the linker in Symantec C++ v8.0 does not yet support the creation of code resources, there is a way to create a code resource from a PowerPC application using Symantec Rez. Symantec C++ v8.0 includes a Code Resource project model which does this.
The Code Resource project model consists of two projects. The first, Code Resource.Π, is similar to a Mac Application project, but doesnt include InitToolbox() (its unnecessary in a code resource). It uses the rsrcMPWPPCRuntime.o runtime library instead of PPCRuntime.o, and PPCLink & MakePEF instead of the internal linker.
In PowerMac applications, constructors and destructors for global and static objects are called automatically by __cplusstart(), which the linker assigns as the main entry point to your application (not main()). This routine calls your constructors, initializes your QuickDraw globals, calls your main() function, and then calls your destructors.
In a shared library, constructors for global and static objects are called by __cplusinit, which the linker assigns as an initialization routine. The Code Fragment Manager will automatically call this initialization routine when your shared library is loaded. The __cplusinit() routine will also hook your shared librarys QuickDraw globals into the QuickDraw globals of the calling application. Destructors for global and static objects are called by __cplusterm(), which the linker assigns as a termination routine. The Code Fragment Manager will automatically call this termination routine when your shared library is unloaded.
In code resources, there is no way to automatically call constructors or destructors for global and static objects, or hook QuickDraw globals, and still preserve the arguments passed to main(). Instead, you must call routines to do this for you. In C, you use __rsrcinit() and __rsrcterm(), declared in stdlib.h. In C++, you use __cplusrsrcinit() and __cplusrsrcterm(), declared in new.h. The C++ initialization and termination routines call the C initialization and termination routines. Use only the C++ or C initialization routines. Do not use both. These routines are defined in the rsrcMPWPPCRuntime.o library.
If your code resource is called only once to perform its function, call __rsrcinit() or __cplusrsrcinit() at the start of your program, and __rsrcterm() or __cplusrsrcterm() at the end.
If your code resource is reentrant, call __rsrcinit() or __cplusrsrcinit() only the first time your code resource is called, and __rsrcterm() or __cplusrsrcterm() the last time your code resource is called.
Do not use any QuickDraw globals, or any global or static objects that rely on their constructor, before calling __rsrcinit() or __cplusrsrcinit().
The second project in the Code Resource project model will copy the data fork of the target built by Code Resource.Π into a resource and prepend a routine descriptor to it. Code Resource.Π is included as a sub-project to the second project. Debugging is disabled for the sub-project to ensure that the sub-projects target is built instead of a temporary instant-run PEF when the parent project is brought up to date.
Code Resource.Π includes two resource (.r) files, _CopyToResource.r and __AppendRoutineDescriptor.r.
_CopyToResource.r reads the data fork of the sub-projects target and stores it into a temporary resource.
__AppendRoutineDescriptor.r prepends a routine descriptor to the temporary resource and stores it in your final resource. Before you build your code resource, you will need to modify a number of #defines in this file. The file contains comments that describe the necessary changes.
The Always check file dates option is enabled in the second project to ensure that the resource description files dependency on the sub-projects target is properly tracked.
__AppendRoutineDescriptor.r is dependant on _CopyToResource.r. These files have been named to compile in the right order.
Once the parent project has been brought up to date, your accelerated code resource will be stored in the projects resource file (<projectname>.rsrc).
Q: How do I create a fat or safe fat code resource?
A: You can build a fat or safe fat code resource in much the same way that you would create an accelerated code resource, discussed above. The Code Resource project model includes support for these fat code resource types, as well as a few others. See the comments within the project model for details.
Q: Why are my structs a different size in my PowerPC project than they are in my 68K project?
A: The MC68000 chip must reference word or long values from even addresses. More recent chips in the 680x0 family do not have this limitation, but perform faster when referencing word or long values from even addresses. The 68040 and PowerPC chips perform even faster with structures aligned on 4-byte boundaries.
If you need to share data structures in memory between 68K and PowerPC code (e.g. when passing data to the Macintosh Toolboxs pre-existing 68K-based interfaces), or need to read or write data structures from/to disk with both 68K and PowerPC code, you will need to ensure that your alignment settings match in both your 68K and PowerPC projects.
By default, the PowerPC compilers align fields within structs on 4-byte boundaries. By default, the 68K C++ compiler aligns fields within structs on 2-byte boundaries. Think C always aligns fields within structs on 2-byte boundaries.
The PowerPC compiler supports the following #pragma directive to enable 68K (2-byte) structure alignment in a given structure declaration :
#pragma options align=mac68K
/* Your struct declaration */
#pragma options align=reset
Q: My 68K application, created with the Visual Architect in v7.0(.x), works fine. Why does a fat version of the same application not run on a 68K Mac?
A: Because of changes in the TCL, you will need to re-compile the 68K application with the 68K environment and TCL included in version 8, and re-merge it into your fat application.
Q: When I run my program with the debugger, it launches Power Mac DebugServices. This program remains running invisibly. How can I quit this application when I am done debugging?
A: You can write an AppleScript that contains the following :
tell application "Power Mac DebugServices" to quit
Never run this script while debugging. To ensure that DebugServices has quit when no longer needed, name the script ShutDown, and put it in your (Scripts) folder. The script will be run when you quit the Symantec Project Manager.
Q: Can I use Apples new Toolbox Assistant with the Symantec Project Manager?
A: Yes. The Symantec Project Manager supports both The THINK Reference and QuickViewer. It is capable of using both simultaneously.
As with the Think Project Manager, the Symantec Project Manager will allow you to reference the Think Reference or QuickViewer directly if an alias to it, named exactly THINK Reference or Primary Doc Server, is located in your (Tools) folder. The Symantec Project Manager considers these names synonymous. The Symantec Project Manager will search a second documentation server if its unsuccessful in finding a match in the first. The second documentation servers alias must also be located in the (Tools) folder and must be named Secondary Doc Server.
Q: When I convert my Think Project Manager project, the Symantec Project Manager preserves the segmentation in groups. Is there a way around this?
A: Yes, hold down the shift key when opening the Think Project Manager project.
Q: How do I Check In files to my SourceServer database for the first time? And how do I Check Out files from a SourceServer database that Ive never checked out before?
A: To do these actions, you must send the command to SourceServer manually. The Symantec Project Manager includes a Worksheet window, available under the Windows menu, that you can use to send commands to SourceServer or ToolServer.
Example of a CheckIn command :
CheckIn -new "filename.cp"
Q: Can I use Check In on the Revision menu to check in header files to a SourceServer database?
A: Yes. In the project Options dialog, on the Extension settings page, add .h to the list of supported filename extensions, but do not specify a translator. You will be able to add files with names ending in .h to your project, but they will not be compiled. You can then check these files into your SourceServer database by selecting them in the project window, and then selecting Check In from the Revision menu.