extern const char* const SOME_CONSTANT giving me linker errors

c++ linker constants extern
AndiDog picture AndiDog · Feb 20, 2013 · Viewed 8.6k times · Source

I want to provide a string constant in an API like so:

extern const char* const SOME_CONSTANT;

But if I define it in my static library source file as

const char* const SOME_CONSTANT = "test";

I'm getting linker errors when linking against that library and using SOME_CONSTANT:

Error 1 error LNK2001: unresolved external symbol "char const * const SOME_CONSTANT" (?SOME_CONSTANT@@3QBDB)

Removing the pointer const-ness (second const keyword) from both the extern const char* const declaration and the definition makes it work. How can I export it with pointer const-ness?

Answer

Angew is no longer proud of SO picture Angew is no longer proud of SO · Feb 20, 2013

The problem could be that the extern declaration is not visible in the source file defining the constant. Try repeating the declaration above the definition, like this:

extern const char* const SOME_CONSTANT;  //make sure name has external linkage
const char* const SOME_CONSTANT = "test";  //define the constant

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