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Think Top 10

By Scott Shurr, Symantec Technical Support, Symantec Corp.

Q. I changed a library in my project, and now I get link errors that say __noMethod and __noObject are undefined. Why?

A. These 2 functions are called from oopsDebug or oopsDebug++. The libraries call __noMethod when a message lookup fails, and __noObject when a message is sent to a bad object pointer or handle. These functions, declared in oops.h, allow your application to catch potentially fatal errors, and take the appropriate action. You must provide the code which defines the functions. For example:

/* 1 */
void __noMethod(void) { printf("Method lookup failed\n"); exit(1); }

Q. My project is using classes based on Pascal Objects. Are there any advantages to changing it to use pointer based objects?

A. Yes. Pointer based objects require less special treatment. Since they are not handles, they will never move, and you don’t need to worry about locking and unlocking them. Also, you will no longer need to keep track of when you are using a pointer, and when you are using a handle, so dereferencing becomes less of an issue. Another reason is that Pascal objects are not part of the C++ standard, which is a problem if you want to port your code to another platform.

Q. What are the advantages of moving the application I wrote with TCL 1.1.3 up to TCL 2.0?

A. First, TCL 2.0 uses pointer based objects instead of Pascal Objects. You can now use all of the nice features of C++ like multiple inheritance. Also, there are new classes that make it relatively easy to add features like scriptability to your application.

Q. I updated to C++ 7.0. Now I am getting warnings like the following (in this case while precompiling TCL #includes.cpp): File <Exceptions.h>; Line 71; While compiling <TCL #includes.cp> Warning: unrecognized pragma. What’s the problem?

A. The behavior of the 7.0 C++ translator in response to unknown pragmas has changed. In old versions, unrecognized pragmas were simply ignored. Now, they are flagged by warnings. The guilty pragma: #pragma nooptimize(CatchException) was unrecognized in C++ 6.0.x, but the compiler didn’t complain. It is safe to ignore the warning. You can disable the warnings, if you like, by going to Edit:Options:Symantec C++...:Warning Messages and unchecking the Unrecognized pragma box.

Q. I had to change some of my #pragma statements in order to fix link errors for my templates after I upgraded to C++ 7.0. For instance, the 6.0.x Vector Project gave me errors like this: undefined: operator <<(ostream&,vector<char>&) (main.cp) Why did this change?

A. Templates at 6.0.x could cause problems because the response to #pragma template TemplateName<type> was to instantiate every method in the TemplateName class. The expansion of large templates could result in code that would exceed the 32K segment size, and there was no way short of redesigning the project to get around it. In the 6.0.x Vector Project, for example, the statement: #pragma template vector<char> in the file vector<char>.cp caused the vector class for char, as well as the << operator and other methods, to be instantiated. In 7.0, you have to tell the compiler exactly where to instantiate the class and each of its methods. That’s why you need the line: #pragma template operator <<(ostream&, vector<char>&) to fix the link error. The increased control afforded by this change solves the segment size problem by allowing you to instantiate the class and its methods in different files in different segments. In general, the changes give the programmer more flexibility in generating the template instantiations.

Q. I have several projects that share the same resources. Is there any way to avoid having to edit the <ProjectName>.rsrc for each project whenever I want to change the resources?

A. Yes. The Resource Copier translator exists for that purpose. What it does is takes the contents of each .rsrc file in the project window and, when you bring the project up to date, updates the <ProjectName>.rsrc by copying any new or changed resources into that file. To share some resources between ProjectA and ProjectB, you could create a SharedResources.rsrc file, and add that file to each project. When you bring ProjectA up to date, the resources in SharedResources.rsrc will be copied into ProjectA.rsrc. ProjectB will work the same way. When you want to change the resources, run ResEdit on SharedResources.rsrc instead of ProjectA.rsrc or ProjectB.rsrc.

Q. Can I mix .rsrc and .r files in the same project?

A. Certainly. THINK Rez is just like the Resource Copier in its treatment of the <ProjectName>.rsrc file. The changes to any .r file in a project will be copied into the <ProjectName>.rsrc file when you bring the project up to date. It is okay to mix .r and .rsrc files in the same project, as long as the resource types and numbers are unique.

Q. Are there any online sources for patches?

A. Yes. Here is the list:

AppleLink: To find patches, follow the path: Support:Third Parties:Third Parties (P-Z):Symantec Solutions:Software Updates and Solutions:Think C/Symantec C++ Updates

CompuServe: To find patches: GO SYMDEVTOOLS, and BROWSE through library 2 for C patches, library 11 for C++ patches.

Symantec BBS: Call 503-484-6669 @9600 or 503-484-6699 @2400.

America Online: To find patches: keyword ‘Symantec’, click on Software Library

Internet (FTP): anonymous ftp to sumex-aim.stanford.edu. The path to patches is info-mac/lang

Q. I can’t get the TPM to automatically start up THINK Reference, even though I put “THINK Reference alias” into the Tools folder. Why doesn’t this work?

A. Items in the Tools folder should be the exact name of the program you wish to use. You must edit “THINK Reference alias” to be “THINK Reference”. To use another program like ToolServer, put in “ToolServer”, not “ToolServer alias.”

Q. The sizeof operator doesn’t work. The following statement prints 0: printf("%d\n",sizeof(int));

A. The problem is that sizeof returns a long, not an int. This works: printf("%ld\n",sizeof(int));