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Asked: 2026-05-11T08:44:00+00:00

I am working on a game and have an interesting question. I have some

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I am working on a game and have an interesting question. I have some game-wide constant values that I want to implement in one file. Right now I have something like this:

constants.cpp

extern const int BEGINNING_HEALTH = 10; extern const int BEGINNING_MANA = 5;

constants.hpp

extern const int BEGINNING_HEALTH; extern const int BEGINNING_MANA;

And then files just #include ‘constants.hpp’ This was working great, until I needed to use one of the constants as a template parameter, because externally-linked constants are not valid template parameters. So my question is, what is the best way to implement these constants? I am afraid that simply putting the constants in a header file will cause them to be defined in each translation unit. And I don’t want to use macros.

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1 Answer

  1. Get rid of the extern and you’re set.

    This code works perfectly fine in a header, because everything is ‘truly constant’ and therefore has internal linkage:

    const int BEGINNING_HEALTH = 10; const int BEGINNING_MANA = 5; const char BEGINNING_NAME[] = 'Fred'; const char *const BEGINNING_NAME2 = 'Barney';

    This code cannot safely be put in a header file because each line has external linkage (either explicitly or because of not being truly constant):

    extern const int BEGINNING_HEALTH = 10; extern const int BEGINNING_MANA = 5; const char *BEGINNING_NAME = 'Wilma';  // the characters are const, but the pointer isn't
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