Thread: Linker errors with Templates...

  1. #1
    Beginning game programmer Petike's Avatar
    Join Date
    Jan 2008

    Question Linker errors with Templates...

    Hi all,
    I have read that "template classes and functions" must be declared and defined in the same file (in some header file). But I don't want to have the declarations and the definitions in the same file (that is in contrast to what I was learning so long time). Is there any possible solution to have separated the template declarations in header file and the template definitions in .cpp file (without linker errors)?

  2. #2
    Kernel hacker
    Join Date
    Jul 2007
    Farncombe, Surrey, England
    The key here isn't whether something is in the same file or not - it is whether the compiler can see the source code when it compiles or not. You could of course have some of your template code in a .h file, and then include a .cpp file inside that header [or in the main .cpp file]. But I guess that's not what you actually wanted either, so the answer is simply "No, you can't do it any other way".

    The reason is that templates are expanded when the compiler encounters the use of a tempated item. At that point, the compiler must have access to the SOURCE of the template code itself [1], to generate the code for that function.

    [1] Of course, it actually reads all templates and stores them in an internal form, then uses that internal form to generate the functions in the object file.

    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  3. #3
    Beginning game programmer Petike's Avatar
    Join Date
    Jan 2008
    Thanks you very much, Mats

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