Our universitie's homework submission system has - instead of focusing on programming skills - set ridiculous and impractical requirements on submissions. To bypass that, I use preprocesor and few other tricks to merge my homework solution into one file (one of the requirements).
Another requirements is that no warnings must occur - and -Wpedantic is enabled. I forward-declare a struct in node.h so that I can use it in function calls:
typedef struct Edge Edge;
// So that I can do:
typedef struct Node {
void* value;
int name;
Array* edges;
} Node;
Edge* node_find_edge(Node* node, NodeName target);
In a different file - edge.h - full definition reads as:
typedef struct Edge {
size_t cost;
NodeName A;
NodeName B;
} Edge;
I get this warning:
main.c: At top level:
main.c:779:3: warning: redefinition of typedef 'Edge' [-Wpedantic]
} Edge;
^
main.c:753:21: note: previous declaration of 'Edge' was here
typedef struct Edge Edge;
Don't get confused by the "main.c" thing, that simple because the files are merged as I said.
What forward declaration is correct and warningless?
Don't use the typedef, just use struct Edge*
struct Edge; // forward declaration
struct Edge* node_find_edge(Node* node, NodeName target);