Thread: "extern const int" creates linking errors that "extern int" doesn't

Originally Posted by citizen

> ok, I don't understand it
The whole point of the extern keyword is to extend a variable's lifespan beyond file scope. It allows global constants to exist across an entire project.

Vart's quote from the standard states that constants are linked internally in C++ by default, allowing you to initialize a constant in a header file. In the language's predecessor, C, constants weren't allowed to be initialized in header files, so extern was used. C++ supports the extern keyword because it was inherited from C. If someone can prove that a constant must or shall be linked internally, then I'll gladly shut up.

Do you know any good links that have examples of what you just said? For me, it's hard to learn without examples and just by someone's theoretical talk.