Invalid use of incomplete type 'DIR' - c++

Question

I'm trying to compile this code, which works fine on Windows, on Linux (Code::Blocks):
/* Edit: Includes */
#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <...>
/**/
/* === */
/* Function code */
DIR *dp;
dirent *ep;
string name_parent;
dp = opendir(somepath);
name_parent = dp->dd_name; //error
/**/
Since path names on Windows are not case sensitive, I can read a user input like "c://program files" and get the "correct" path "C:\Program Files*" (except for the asterisk - or "F://" -> "F:*"). I also use this variable to get a directory listing with absolute path values, since ep->d_name (after some readdir() of course) returns a path relative to somepath.
On Linux, I get a compiler error (for "dp->dd_name"):
error: invalid use of incomplete type 'DIR'
Did I forget something?
Or is there a logical error?
Edit: I've added the includes (that I'm already using) above.

Answer 1

/* Edit: Includes */
#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <...>
/**/
/* === */
/* Function code */
DIR *dp;
dirent *ep;
string name_parent;
dp = opendir(somepath);
ep = readdir(dp);
name_parent = ep->d_name;
/**/
The variable d_name exists in the struct dirent which gives the name of the directory

Answer 2

You didn't declare the type of DIR! On Posix systems, you would have said,
#include <sys/types.h>
#include <dirent.h>
However, on Windows, you don't have these features. Instead, you could use the Windows API filesystem functions.

Answer 3

yes. you missed including header files.
dirent.h

Answer 4

The internal structure of a DIR is unspecified, so you should never rely on it and expect your code to be portable.
The glib source for Windows says this about DIR:
/*
* This is an internal data structure. Good programmers will not use it
* except as an argument to one of the functions below.

Answer 5

Apparently, the type DIR is not defined at the point you're trying to use it. Maybe you forgot an #include?

Answer 6

It is not about to forget including some headers or definition now I've faced this problem but not error it was warning.
My files.h;
class Files
{
public:
explicit Files(const char *p_path = 0);
~Files();
/* .... */
private:
std::string path;
}
My files.cpp;
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <sys/types.h> // I added this line with #Kerrek SB's advice but nothing changed
#include <dirent.h>
#include <files.h>
static DIR *p_dir = NULL;
static struct dirent *p_ent = NULL;
Files::Files(const char *p_path)
{
if (p_path == NULL)
{
std::cerr << "PATH is NULL" << std::endl;
exit(EXIT_FAILURE);
}
path = p_path;
p_dir = opendir(p_path);
if (p_dir == NULL)
{
std::cerr << "Cannot open " << path << std::endl;
exit(EXIT_FAILURE);
}
}
Files::~Files()
{
if (p_dir)
{
/* Here is my warning occuring in this line and the definition
line p_dir 'static DIR *p_dir = NULL' */
delete p_dir; // After changing this line with 'free(p_dir);' warnings gone.
p_dir = NULL;
}
}
The warning at the definition line (static DIR *p_dir = NULL;) is 'p_dir' has incomplete type and the warning at the delete line (delete p_dir;) is possible problem detected in invocation of delete operator: [-Wdelete-incomplete].
After changing the delete p_dir; with free(p_dir); the both warnings are gone.
I don't know it's exact reason but it sounds like DIR * type acting like void *. I'm just taking a wild guess.
Hope this helps.