How do you prevent names from colliding in C

Question

Let's say I have a two files : stack.h and queue.h. Both want to implement the function add(). If I include stack.h and queue.h in the same main.c for example, there will be a collision.

What is the recommended way to implement the add() function in both files?

As the other answers said, and as in any programming language, all libraries you include must have a sane design with dedicated names which you accept. Otherwise, you will always have collisions in any programming language. Eg, if you include a header "terribad.h" which happens to reserve all variables on the planet, you might want to reconsider having "terribad.h" inside your project. — Dmitry, Feb 28 '13 at 00:09

Ben Zotto · Answer 1 · 2013-02-28T00:30:40.227

6

If this is pure C, the simplest common solution is to use do-it-yourself namespacing on the functions relative to the name of the module or data structure that they apply to. e.g.

stack_add(...)
queue_add(...)

You will find examples of this in pretty much all large pure-C projects:

pthread_mutex_lock() // POSIX/UNIX, used for locking a mutex
CGRectMake()         // iOS, used to fill in a CGRect structure
RtlZeroMemory()      // WinNT, "Rtl" indicates the module it belongs to

edited Feb 28 '13 at 00:30

answered Feb 28 '13 at 00:08

Ben Zotto

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See this question for ideas on C namespaces, although IMHO it's a bit overkill: http://stackoverflow.com/questions/389827/namespaces-in-c – congusbongus Feb 28 '13 at 00:10

Aniket Inge · Accepted Answer · 2013-02-28T00:19:43.843

If you already have a queue and a stack implementation tested, and referred to elsewhere.. you can do some preprocessor tricks like this:

#define _STACK
#define _QUEUE

#ifdef _QUEUE
#define add queue_add
  #include "queue.h"
#undef add
#endif

#ifdef _STACK
#define add stack_add
  #include "stack.h"
#undef add
#endif

int main()
{
   stack_add();
   queue_add();
}

My advice is - refactor the code base to use non-clashing naming convention instead of generic function names like add and subtract and the rest.

If you are a fan of object oriented programming style and like the whole "add", "modify" concept then use function pointers inside the queue and stack structure.

#define TYPE int

typedef struct tagStruct{
   TYPE *dataBuffer;
   void (*add)(TYPE data);
   void (*modify)(TYPE data, int index);
   void (*deleteEverything)()
}stack;

and in the init(stack) method, assign add(), modify() and deleteEverything() to different functions that have no name-collision(likewise for queue)

Then you begin to see stack and queue as ENTITIES rather than bunch-of-functions.

You can then do this:

stack stc;
init(stc); /*sets up the function pointers*/
stc.add(10);
stc.modify(30,0);
stc.deleteEverything();

@KeithNicholas yeah - but if he already has stack and queue defined, he will have to do something ugly. Just so he does not break other parts of the code that either use `stack.h` or `queue.h` — Aniket Inge, Feb 28 '13 at 00:12

How do you prevent names from colliding in C

2 Answers2