error: dereferencing pointer to incomplete type

What the does this error mean its so frustrating.
basically i have a struct created in main

Code:

---

struct Ethfrm_t
{
        struct FCfrm_t* ptr;
        struct FIPfrm_t* FIPptr;
        unsigned char DestEthAdr[6];
        unsigned char SrcEthAdr[6];
        UINT32  VLAN_HdrSave;
        UINT32  reserved;
        UINT32  pad;
        unsigned char Ethbuffer[BUF_SIZE];
}  __attribute__ ((packed));

---

then i have
typedef struct Ethfrm_t Ethfrm_t; On a header file on the top of most header files

but when i made a functions file *.c When i use that Struct i get that warning all the time

Code:

---

void printEthfrm(Ethfrm_t * Ethfrm){
        unsigned char* etherhead = Ethfrm->Ethbuffer;                ////right here
        printf("EtherType error ");
}

---

Basically it means that at the point where you attempt to use that struct, the compiler does not have a definition of the struct available to it. You said that you've got the typedef in the header but the struct definition itself is in some other source file (with main function)? The definition should be in the header if you're going to use it in multiple files.

Okay well this is retarded but now i put it in a header

Code:

---

typedef struct Ethfrm_t
{
        struct FCfrm_t* ptr;
        struct FIPfrm_t* FIPptr;
        unsigned char DestEthAdr[6];
        unsigned char SrcEthAdr[6];
        UINT32  VLAN_HdrSave;
        UINT32  reserved;
        UINT32  pad;
        unsigned char Ethbuffer[BUF_SIZE];
}  __attribute__ ((packed)) Ethfrm_t;

---

I get this error
server.h:11: error: redefinition of ‘struct Ethfrm_t’
server.h:20: error: redefinition of typedef ‘Ethfrm_t’
server.h:20: error: previous declaration of ‘Ethfrm_t’ was here
iono what its problem is but i doesnt like me putting Ethfrm_t on the top and bottom????? Y

Quote:

---

Originally Posted by kiros88

Okay well this is retarded but now i put it in a header

---

Did you put it anywhere else as well?

IF NOT: I don't use the same name at both ends; it shouldn't matter I think but if that fixes it, then there you go.

That sounds like you are including the same header more than once. That's fine to do from a style perspective, but you need include guards to prevent the compiler from reading the same code twice. I'll let someone else post a link on include guards, or you can just google.