Symantec Top 10

This monthly column, written by Symantec’s Technical Support Engineers, aims to provide you with technical information based on the use of Symantec products.

By Noah Lieberman and Andy McFarland, Symantec Technical Support

Q: I want to use QuickDraw 3D in my application. Is there anything special that I need to do to use it with Symantec C++ for the Power Macintosh?

A: Yes. There are some slight changes that must made to the interfaces and sample projects. We have a patch kit available that will allow you to use our compiler and has sample projects for all of the demos. You must also make sure that you have the QuickDraw GX headers. QuickDraw 3D interfaces and libraries are avilable from Apple as part of their MacOS SDK subscription.

Q: I have some binary data that was written with a MSDOS program that I want to read into my Macintosh program, but the numbers are all messed up. Why?

A: The two systems save numbers differently. The Motorola processors use big-endian numbers, and the Intel processor machines use little-endian numbers. There is a difference in how numbers are stored in memory and on the disk. For example, the long hexadecimal value $12345678 would be stored by an Intel processor as $34127856.

To convert a number as you read it into a Macintosh, you can use the following C code:

        long    longVal = ReadALong(srcFile); // read a long from the       // file
        char    *cp = (char*) &longVal;
        char    temp;

        temp = cp[0];
        cp[0] = cp[1];
        cp[1] = temp;

        temp = cp[2];
        cp[2] = cp[3];
        cp[3] = temp;

Of course, if you are real ambitious, the assembly code is MUCH simpler and faster:

        MOVE.L  longVal,D0
        ROR.W   #8,D0
        SWAP    D0
        ROR.W   #8,D0
        SWAP    D0
        MOVE.L  D0,longVal

So you could define the code like this for 68K:

 #pragma parameter __D0 Little2BigEndian(__D0)
 pascal long Little2BigEndian(long val) = {
        0xE058,         // ROR.W    #8,D0
        0x4840,         // SWAP     D0
        0xE058,         // ROR.W    #8,D0
        0x4840          // SWAP     D0
        };

        long  longVal =   Little2BigEndian(ReadALong(srcFile));

Q: I am using SPM 8.0.x and have created an array of 50 elements. However, when I look at the array in the debugger only the first 25 elements are displayed (0-24) in the data window. Is there now a limit to the number of array elements that can be displayed in the data window and if so, how do I view the values in the latter elements of my array?

A: There is an option in the SPM debugger, under the data menu, to set the array bounds. The default setting is 25 elements, starting from element 0 and ending with element 24. The upper limit of the array bounds is 32767 elements (0-32766) that can be displayed and you can display any subset of your array by setting the starting element (lower bounds) and the number of elements you want to display (display range).

Q: I am getting Undefined MyClassName::_VTBL what does it mean?

A: This is caused by declaring a function in the header file but not defining it in the source file.

Q: Is there any way to change the order in which code is compiled in the Symantec Project Manager?

A: You can set the “Save Project as Script” script to save the project as a script, physically change the lines in the script to reflect the desired build order, and then rebuild the project using the script.

Q: I have a 7.0.x VA application that I want to port to PowerPC, but if I open it with 8.0 and click the convert button in the conversion dialog, I am getting compiler and linker errors. Are there any alternate methods for updating to PPC?

A: Yes. Usually most of these errors are due to the lack of neccessary libraries. Create a new VA app with 8.0, and add your source files and VA Resource. This way the 8.0 VA project model will add the basic libraries for you.

Q: My code works fine on 68k but its crashing on PowerPC.

A: The PPC forces 4 byte struct alignment, which can often cause problem when converting from 68k. There is a pragma you can use to get around this problem:

 #if defined(powerc) || defined (__powerc)
 #pragma options align = mac68k
 #endif
 struct myRecord
 {
 OSType theOSType;
 unsigned short  theSize;
 };
 #if defined(powerc) || defined(__powerc)
 #pragma options align = reset
 #endif

Q: When I call x80told it sets the 8 bytes following the long double to 0.

example:

 void main()
 {
 long double   ld1, ld2;
 extended80 x80;

 ld2 = 131.416726;
 ldtox80(&ld2, &x80);
 x80told(&x80, &ld1);//when this is called, ld2 is set to 0
 } 

A: Apple’s MathLib expects true long doubles which are 16 bytes. You can get around this by passing an array of long double (i.e. long double ld1[2]).

Here is an example:

 void main()
 {
 long double   ld1[2], ld2;
 extended80 x80;

 ld2 = 131.416726;
 ldtox80(&ld2, &x80);
 x80told(&x80, ld1); // by passing the array, ld2 maintains it            // value
 }

Q: I rebuilt my PPCAnsi.o file with gla_alloc.c, but when I try and compile my project with this new file I get the error: “PPCANSI: specified file not recognized as a valid object”.

A: The Toolserver may not be installed on your Hard Disk. If this is the case you need to copy the toolserver folder from the Symantec C++ CD, and place an alias of Toolserver in your (Tools) folder.

Another possibility is that the modifications were made to the Shared Library PPCAnsi project instead of the Static Library project. gla_alloc.c needs to be added to the PPCAnsi_xcoff.Π project found in the Headers and Source folder in your Standard Libraries folder.

Q: I want to put a CStyleText into my view in VA, but there isn’t a tool for it in the tool palette.

A: Choose Classes from the edit menu. Enter the name of your new class (i.e. CMyStyleText) that will be derived from CStyleText. Choose CEditText from the Base Class: popup menu. Enter CStyleText into the Library Class: box; CMyStyleText will now be derived from CStyleText. Now use the Panorama tool from the tool palette to place a pane into your view. Select the pane, go to the Class submenu under the pane menu and select CMyStyleText.

Note: Normally the Library Class: box is for a class you have already derived from the Base Class, but this also works with other TCL classes as long as they are derived from the Base Class. For more info see p. 30-8 in the 8.0 User’s Guide, or p. 241 in the 7.0 Visual Architect and THINK Class Library Guide.

Special Thanks to Michael Hopkins, Craig Conner, Mark Baldwin, Scott Morison, Levi Brown, Steve Howard, Kevin Quah, Glenn Austin.