global constants without using #define

Question

Ok, I'm looking to define a set of memory addresses as constants in a .h file that's used by a bunch of .c files (we're in C, not C++). I want to be able to see the name of the variable instead of just seeing the hex address in the debugger... so I want to convert the #defines I currently have into constants that are global in scope. The problem is, if I define them like this:

const short int SOME_ADDRESS  =  0x0010

then I get the dreaded "multiple declarations" error since I have multiple .c files using this same .h. I would like to use an enum, but that won't work since it defaults to type integer (which is 16 bits on my system... and I need to have finer control over the type).

I thought about putting all the addresses in a struct... but I have no way (that I know of) of setting the default values of the instance of the structure in the header file (I don't want to assume that a particular .c file uses the structure first and fills it elsewhere.. I'd really like to have the constants defined in the .h file)

It seemed so simple when I started, but I don't see a good way of defining a globally available short int constant in a header file... anyone know a way to do this?

thanks!

Answer 1

Declare the constants in the header file using extern:

extern const short int SOME_ADDRESS;

then in any, but only one, .c file provide the definition:

const short int SOME_ADDRESS = 0x0010;