CODEWITHSUNDEEP
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Steve
Steve

Reputation: 859

Circular dependency between C header files

Does anybody have any tip how to handle the symbolic constants and types definition in large program in a system manner to avoid circular dependencies between the header files? I have an idea to define one header file which will contain all structs, unions and enum types definitions and another header file which will contain all symbolic constants definitions. But I have doubts as far as this solution regarding to implementation hiding. Thank you for any ideas.

Upvotes: 8

Views: 11021

Answers (3)

Lundin
Lundin

Reputation: 214730

The solution is to simply use some manner of program design. Each "object"/"module" in your program should consist of one h file and one c file. The h file is the public interface. Each such object should only be concerned with its own designated task. It should only include the resources needed to perform that task.

With such a design, there should never be any circular dependencies, or the design is flawed. You should not fix a bad design with various code tricks, you should re-do the design.

But of course the same resource could be included multiple time from different parts of the code. This is why we always use header guards in every single h file.

Upvotes: 4

Chris Turner
Chris Turner

Reputation: 8142

You can separate out the typedef statements from the actual struct definitions and place them before including the other headers. This way if your datatype foo contains a member of type bar *, it doesn't need the definition of bar straight away - it'll be happy enough knowing that it's a valid datatype that will get resolved later. 

#ifndef FOO_H
#define FOO_H

typedef struct foo_s foo;

#include "bar.h"

struct foo_s
  {
  bar *my_bar;
  };
#endif

.

#ifndef BAR_H
#define BAR_H

typedef struct bar_s bar;

#include "foo.h"

struct bar_s
  {
  foo *my_foo;
  };
#endif

Upvotes: 9

Hans Petter Taugbøl Kragset
Hans Petter Taugbøl Kragset

Reputation: 999

In any given header file, put

#ifndef FILENAME_H
#define FILENAME_H

struct a {}
union b {}

function c();
#endif

This will cause the file to be included only once.

Upvotes: -1

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