.c FIle Dedicated to Data

Question

Is it completely unheard of to have a .c file dedicated to just data? In my case, I'd be using it for global variables that are shared across two other .c files. Here's specifically how I'm using it.

// serverth.h

struct serverth_parameters {
    struct { // right now, this is the only struct needed
        char * root,
             * user,
             * public,
             * site;
    } paths;

    // I anticipate needing another struct here

};

#ifndef SERVERTH_SOURCE
extern struct serverth_parameters parameters;
#endif

---

// serverth.c

#define SERVERTH_SOURCE
#include "serverth.h"

struct serverth_parameters parameters = {
    .paths = { // macros are actually used here
        "/srv",
        "/user",
        "/public"
        "/site"
    }
};

---

parameters is a struct that's used for a websockets server, in two files:

• One for HTTP (uses parameters.paths.site)
• Two for proprietary protocols (both use .paths.user, one uses paths.public)

Is this a bad practice? Do people do this? Or, is it more conventional to just keep the data in the source file in which it is most relevant?

Answer 1

In general I'd be wary of "dumping ground" files, where one would start listing global variables or long lists of #defines.

However, if by "globals" you actually meant that these globals would be constants, then that would seem acceptable, as long as they are structured and re-grouped in meaningful patterns, and that the extent of their reuse justifies to extract them to a separate file.

If these conditions aren't satisfied, then I'd usually restrain them to the file where they're expected to be used, if possible.

Include Guards

On a different note, I don't know how your files are compiled and what build system you use, but you might want to use compilation guards of the form:

#ifndef MY_MODULE
# define MY_MODULE

/* stuff here */

#endif