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HP OpenVMS Systemsask the wizard |
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The Question is: CXXLINK with local "header_files.h" DEC C++ V6.0-001 on OpenVMS Alpha V7.1 Mr. Wizard, When ever I compile my class definitions, I never see any entries in the repository directory expect for CXX$DEMANGLER_DB (which is empty). (But I always see *.OLB files in the repository when I compile examples from SYS$COMMON:[SYSHLP.EXAMPLES.CXX]) When I link with a driver program, such as to test my list, queue, or stack classes, I then see entries in the repository, but only if my header files are declaired as local #include "list.hpp", "queue.hpp", etc... and are in the same directory as the source and object files. But when I place the header files in a common area/directory such as #include "usr01:[public.inc]list.hpp" #include "usr01:[public.inc]queue.hpp", etc.. all of my programs compile fine, just like as before but when I try to link them (driver)I get the following message: %LINK-W-USEUNDEF, undefined symbol List<int>::List() referenced. Other undefined symbol messages reference other member functions of my list class. This problem occurs with all of my programs only when my local header files are not in the same directory as the source or object files. Please tell me what's going on because I would like to have all of my header files in a common directory, just like I do with my 'C' header files. And could you please explain to me how the repository works or where I can find some info on it, because I cannot find any repository info in any of my documentation. By the way, my driver program has the following include statement: #include "usr01:[public.inc]list.hpp" and it compiles with no problems, and there are no entries in the repository. Thanks, Terry D. Frierson The Answer is : Without an example of the problematic source code and the associated error messages, the OpenVMS Wizard can only guess -- the OpenVMS Wizard can only guess that the problem involves the template declaration files, and specifically that the template declaration files are not in the same directory as the template definition files. When code is "templatized", the C++ compiler needs to have access to all of the template function definitions at compile time in order to instantiate them. Thus all the template function definitions must be located in header files. The definitions can either be placed in the same header file as the template declarations (eg: list.hpp would contain the definitions), or they can be put in a special template definition header file -- a file which must have the same prefix as the template declaration file (list) and one of a special set of suffixes (i.e. .cc, .cxx). This template definition header file should be put in the same directory as the template declaration file. For a simple example, please see the section "How to organize Your C++ code" (in Section 3.4 in the current edition) of the C++ Users Guide.
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