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Templates and multiple-file projects

Posted on 2004-10-12
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Last Modified: 2012-06-27
How can I handle Templates in multiple-file projects? Please explain...

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Question by:msjammu
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jkr earned 125 total points
ID: 12288635
You need to provide the template implementation in the header files and include them in each file. Even though the C++ standard would allow to separate the implementation from the declaration, there's no compiler out there that can handle that.
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by:stefan73
ID: 12289339
Hi jkr,
g++ had something close with its #pragma interface and #pragma implementation. I think this was abandoned in the 3.x versions.

The problem is always that multiple instances of template methods or functions are created and must be discarded by the linker - otherwise the final executable would be totally bloated.

Some compilers, such as SUN's CC, create temporary directories to counter the problem. As long as the directory where you compile your files is the same for all involved .cpp or .C files, there are no multiple instances created.

Cheers!

Stefan
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by:msjammu
ID: 12295163
Stefan,
you mean with g++ I can have templates with my multi-files project, with no problems?
I use VC++ 6.0 SP6. Does not it seam to support it??

Many Thanks !
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Assisted Solution

by:itsmeandnobodyelse
itsmeandnobodyelse earned 125 total points
ID: 12300303
jkr has it right. If you want to provide easy-to-handle template classes put all implementation to the header files (directly in the class definition or as inline functions) that should be stored to a shared project directory (you may add that direcory to Tools-Options-Directories-Include Files or to the 'Additional Project Include Directories' in Project Settings). Then, by simply including the class headers you may use these templates in multiple projects.

All other solutions are much less flexible or differ between Platforms/Compilers, e. g. you can move class implementation to cpp files, *but* need to have separate cpp sources where you make instances of your template classes for any type you are using. There you have to include the cpp files (!) of your template class implementation. Some Compilers also have #pragma interfaces that were able to create template instances (the template code for a specific type).

Regards, Alex
 
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by:msjammu
ID: 12305317
Thank Your all experts for there help
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