Jun 94 Top 10
Volume Number: 10
Issue Number: 6
Column Tag: Think Top 10
Think Top 10 
By Scott Shurr, Symantec Technical Support, Symantec Corp.
This is a monthly column written by Symantec’s Technical Support Engineers
intended to provide you with information on Symantec products. Each month we cover
either a specific application of tools or a “Q&A” list.
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 ; Line 71; While
compiling 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&)
(main.cp) Why did this change?
A. Templates at 6.0.x could cause problems because the response to #pragma
template TemplateName 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 in the file vector.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&) 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 .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 .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
into the .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));