Question

I’m writing a small C program that loads a linked list with file names (only). I’m gonna iterate through this list and parse the content of each file name.

When compiling I receive the following error:

main.c: In function 'main':
main.c:25: error: dereferencing pointer to incomplete type
main.c:26: error: dereferencing pointer to incomplete type
make: *** [main.o] Error 1

main.c:

#include <stdio.h>
#include <stdlib.h>

#include "list.h"

int main(int argc, char *argv[])
{
    FNODEPTR node = NULL;

    node = create_filename_list();

    add_filename_node(&node, "file1.txt");
    add_filename_node(&node, "file2.txt");

    //Start Logger
    //Watchdog
    //Warehouse 

    //print_filename_list((struct sFilename *)node);

    while(node!=NULL)
    {
        printf("%s\n",node->chaFilename); //Line 25
        node=node->next; //Line 26
    }

    destroy_filename_list(node);

    exit(0); //0 SUCCESS - 1 FAIL
}

list.c:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>


#include "list.h"

struct sFilename
{
    char chaFilename[25];
    struct sFilename *next;
};

FNODEPTR create_filename_list()
{
    FNODEPTR node = NULL;

    node = (FNODEPTR) malloc(sizeof (struct sFilename)); // Alocando um nó do tipo sFilename

    return node;
}

void add_filename_node(FNODEPTR *fnFilename, char *chaFilename)
{
    FNODEPTR head = *fnFilename; // head recebe o conteúdo de anAction. head aponta para o mesmo endereço que fnFilename
    FNODEPTR newNode;

    newNode = (FNODEPTR) malloc(sizeof (struct sFilename)); // Alocando um nó do tipo sFilename

    strcpy(newNode->chaFilename, chaFilename); // Copiando o conteúdo de chaFilename para newNode->chaFilename.

    newNode->next = head; // next do novo nó aponta para o início da lista (fnFilename)

    head = newNode; //head é igual a newNode. head recebe o endereço de memória de newNode. head está na mesma posição que newNode
    *fnFilename = head; //o conteúdo de anAction é igual a posição de head
}

void print_filename_list(struct sFilename *fnFilename)
{
   if (fnFilename == NULL)
          printf("Nao ha arquivos ftp a serem carregados\n");
   else {
          printf("Os arquivos que serao carregados no T020 sao:\n");
          while (fnFilename != NULL) {
                 printf("\t- %s\n", fnFilename->chaFilename);//fnFilename->chaFilename);
                 fnFilename = (*fnFilename).next;//fnFilename->next;
          }
   }
}

void destroy_filename_list(FNODEPTR fnFilename)
{
    if(fnFilename != NULL)
    {
        free(fnFilename);
    }
}

list.h:

#ifndef LIST_H
#define LIST_H

typedef struct sFilename FNODE;
typedef FNODE *FNODEPTR;

FNODEPTR create_filename_list();
void add_filename_node(FNODEPTR *fnFilename, char *chaFilename);
void remove_filename_node(FNODEPTR *fnFilename);
void print_filename_list(struct sFilename *);
void destroy_filename_list(FNODEPTR fnFilename);

#endif

This list will be passed as reference to other functions (modules) that will parse and load the content into a database. Although I can’t use node->chaFilename to open the files I need to load into the DB.

I got a new problem, when I call parser function passing *node as reference compiler complains the same as above. Example:

parser.c:

//Built-in libs
#include <stdio.h>
#include <stdlib.h>

//Homemade libs
#include "parser.h"
#include "list.h"

int start_parse(FNODEPTR *node)
{
    if(node!=NULL)
    {
        printf("Node is not null\n");
        while(node!=NULL)
        {
            printf("\tNode address %x\n", (unsigned int)node);
            node=node->next;
        };
    }

    return 1;
}

parser.h:

#include "list.h"

#ifndef PARSER_H
#define PARSER_H
int start_parse(FNODEPTR *node);
#endif

GCC output:

gcc -Wall   -c -o parser.o parser.c
parser.c: In function 'start_parse':
parser.c:16: warning: cast from pointer to integer of different size
parser.c:17: error: request for member 'next' in something not a structure or union
make: *** [parser.o] Error 1

Any ideas?

Thanks in advance, and sorry for any English mistake.

Answer 1

struct sFilename
{
    char chaFilename[25];
    struct sFilename *next;
};

This should be defined in list.h file, before the statements:

typedef struct sFilename FNODE;
typedef FNODE *FNODEPTR;

EDIT::

int start_parse(FNODEPTR *node) should rather be int start_parse(FNODEPTR node)