I have this problem with circular dependency in C, I looked around the other questions about this topic but really couldn't find the answer.
I have this first struct named vertex:
#ifndef MapTest_vertex_h
#define MapTest_vertex_h
#include "edgelist.h" //includes edgelist because it's needed
typedef struct
{
char* name;
float x, y;
edgelist* edges;
} vertex;
#endif
The second struct is the edgelist which is included by the vertex.
#ifndef edgelist_h
#define edgelist_h
#include "edge.h" //include edge, because its needed
typedef struct _edgelist
{
edge** edges;
int capacity, size;
} edgelist;
//...
#endif
And then the last struct, the one where the problem raises, the edge struct gets included by the edgelist above.
#ifndef MapTest_edge_h
#define MapTest_edge_h
#include "vertex.h" //needs to be included because it will be unkown otherwise
typedef struct
{
float weight;
vertex* destination;
int found;
} edge;
#endif
I tried everything I could, forward declaring, using #ifndef
, #define
etc. but couldn't find the answer.
How can I resolve this circular dependency problem?
Seems like you shouldn't need to include anything in any of the files. A forward declaration of the relevant types should be sufficient:
#ifndef MapTest_vertex_h
#define MapTest_vertex_h
struct edgelist;
typedef struct
{
char* name;
float x, y;
edgelist* edges; // C++ only - not C
} vertex;
#endif
etc. In C coding, you have to write:
struct edgelist;
typedef struct
{
char* name;
float x, y;
struct edgelist* edges;
} vertex;
This kind of dependency is broken using a forward declaration. Instead of including a file with the full definition of the struct, there are two alternatives:
1.
typedef struct
{
char* name;
float x, y;
struct _edgelist* edges; /* add "struct" here (elaborated type specifier) */
} vertex;
2.
struct __edgelist; /* better form: forward declaration */
typedef struct
{
char* name;
float x, y;
struct _edgelist* edges; /* still need to add "struct" here */
} vertex;
I'm assuming a vertex needs to know what edges connect to it, and an edge needs to know what vertices it connects to.
If it were up to me, I'd create separate data types to associate vertices and edges:
struct vertex {
char *name;
float x, y;
};
// edgelist as before
struct edge {
float weight;
int found;
};
// New struct to map edges and vertices
struct vertexEdge { // you can probably come up with a better name
struct vertex *v;
struct edgelist *edges;
};
// New struct to map vertices and edges
struct edgeVertext {
{
struct edge *e;
struct vertex *vertices;
};
I'm running about 10-12 hours behind on sleep for the week, so I'm pretty sure there's a better way to design the mapping types (probably in a way that doesn't require more than one type), but this is the general approach I'd take.
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