weird typedef struct problems

Hi!

This is my first post on this board, so I would first like to say hello to everybody here!

I want to program a directed graph datastructure. OK, so here are my two types: edges and nodes:

Code:

---

struct node_struct
{
        unsigned int n_e;        // number of connected edges
        struct edge_struct **e;        // array of connected edges (array of pointers to edges)
};
typedef struct node_struct node;

struct edge_struct
{
        float c;                // capacity
        float f;                // flow
        node * u;        // start
        node * v;        // end
};
typedef struct edge_struct edge;

---

Further, I have these functions for memory allocation on the heap.

Code:

---

void alloc_node
(
 node ** u,
 unsigned int n
)
{
        *u = ((node)*) malloc(sizeof(node));
        if(*u == NULL)
        {
                printf("alloc_node: (1) Not enough storage available.\n");
                exit(1);
        }
        (*u)->n_e = n;
        (*u)->e = (edge**) malloc(n * sizeof(edge*));
        if ((*u)->e == NULL)
        {
                printf("alloc_node: (2) Not enough storage available.\n");
                exit(1);
        }
}


void alloc_edge
(
 edge** e
)
{
        *e = ((edge)*) malloc(sizeof(edge));
        if(*e == NULL)
        {
                printf("alloc_edge : Not enough memory available.\n");
                exit(1);
        }
        (*e)->c = 0.0f;
        (*e)->f = 0.0f;
        (*e)->u = 0;
        (*e)->v = 0;
}

---

Well, ok, this compiles fine (under MS VS 2003 Pro), with this main function:

Code:

---

int main()
{
        node * v1;
        //alloc_node(&v1,3);
        edge * a;
}

---

But if I uncomment the second line, then the compiler complains with

f:\src\main.c(18): error C2275: 'edge' : illegal use of this type as an expression

where line 18 eaxtly points to the line holding "edge * a;", so not the call to alloc_node.
But as I said, if I comment the call to the alloc_node, everything compiles fine.

I don't know where my error lies.

Thanks a lot in advance!

Best regards,
Oliver

Baaaaah,

I just found out that this problem just occurs under the Microsoft Compiler. Using gcc, it compiles fine.

Any idea, where the problem is for the Microsoft compiler?

Thanks,
Oliver

Code:

---

struct node_struct
{
    unsigned int n_e;    // number of connected edges
    struct edge_struct **e; // error: struct edge_struct is not declared at this point
};
typedef struct node_struct node;

struct edge_struct
{
    float c;        // capacity
    float f;        // flow
    node * u;    // start
    node * v;    // end
};
typedef struct edge_struct edge;
int main()
{
    node * v1;
    //alloc_node(&v1,3); // v1 is not initialized
    edge * a;
}

---

In C89, once you do an actual bit of code (like calling a function), you can not declare any more variables (so declaring edge * a would be a syntax error). That restriction was relaxed in C99, which gcc follows.