Namespaces in C

Another alternative would be to declare a struct to hold all your functions, and then define your functions statically. Then you'd only have to worry about name conflicts for the global name struct.

// foo.h#ifndef FOO_H#define FOO_Htypedef struct {   int (* const bar)(int, char *);  void (* const baz)(void);} namespace_struct;extern namespace_struct const foo;#endif // FOO_H// foo.c#include "foo.h"static int my_bar(int a, char * s) { /* ... */ }static void my_baz(void) { /* ... */ }namespace_struct const foo = { my_bar, my_baz }// main.c#include <stdio.h>#include "foo.h"int main(void) {  foo.baz();  printf("%d", foo.bar(3, "hello"));  return 0;}

In the above example, my_bar and my_baz can't be called directly from main.c, only through foo.

If you have a bunch of namespaces that declare functions with the same signatures, then you can standardizeyour namespace struct for that set, and choose which namespace to use at runtime.

// goo.h#ifndef GOO_H#define GOO_H#include "foo.h"extern namespace_struct const goo;#endif // GOO_H// goo.c#include "goo.h"static int my_bar(int a, char * s) { /* ... */ }static void my_baz(void) { /* ... */ }namespace_struct const goo = { my_bar, my_baz };// other_main.c#include <stdio.h>#include "foo.h"#include "goo.h"int main(int argc, char** argv) {  namespace_struct const * const xoo = (argc > 1 ? foo : goo);  xoo->baz();  printf("%d", xoo->bar(3, "hello"));  return 0;}

The multiple definitions of my_bar and my_baz don't conflict, since they're defined statically, but the underlying functions are still accessible through the appropriate namespace struct.

When using namespace prefixes, I normally add macros for the shortened names which can be activated via #define NAMESPACE_SHORT_NAMES before inclusion of the header. A header foobar.h might look like this:

// inclusion guard#ifndef FOOBAR_H_#define FOOBAR_H_// long namesvoid foobar_some_func(int);void foobar_other_func();// short names#ifdef FOOBAR_SHORT_NAMES#define some_func(...) foobar_some_func(__VA_ARGS__)#define other_func(...) foobar_other_func(__VA_ARGS__)#endif#endif

If I want to use short names in an including file, I'll do

#define FOOBAR_SHORT_NAMES#include "foobar.h"

I find this a cleaner and more useful solution than using namespace macros as described by Vinko Vrsalovic (in the comments).

You could use the ## operator:

#define FUN_NAME(namespace,name) namespace ## name

and declare functions as:

void FUN_NAME(MyNamespace,HelloWorld)()

Looks pretty awkward though.