C forward declaration of struct in header

Question

I am trying to pass struct pointer in function. I have a typedef in file1.h, and want to only include that header to file2.c, because file2.h only need pointer. In C++ I would just write like I did here, but using C99 it doesn't work. If someone has any suggestions how to pass struct pointer without full definition it would be very appreciated. Compiler - gcc.

file1.h

typedef struct
{
    ...
} NEW_STRUCT;

file2.h

struct NEW_STRUCT;

void foo(NEW_STRUCT *new_struct); //error: unknown type name 'NEW_STRUCT'

file2.c

#include "file2.h"

#include "file1.h"

void foo(NEW_STRUCT *new_struct)
{
    ...
}

Answer 1

I think you just have to name your structure, and do a forward declaration of it and after re typedef it.

First file:

 typedef struct structName {} t_structName;

Second file:

  struct stuctName;
  typedef struct structName t_structName

Answer 2

You may try this:

file1.h

typedef struct _NEW_STRUCT  // changed!
{
    ...
} NEW_STRUCT;

file2.h

struct _NEW_STRUCT; // changed!

void foo(struct _NEW_STRUCT *new_struct); // changed!

file2.c

#include "file2.h"
#include "file1.h"

void foo(NEW_STRUCT *new_struct)
{
    ...
}