Thread: Corrupted double-linked list error

I call a file with the list of months from January-December and store them in a structure of its own.

Then I'm wanting to allocate a 2d array so I can store the counts of the months for each year seen in the next file I'm going to open.

Anyways I'm having issues with this part of my code i believe...


The point of this is to initialize my 2d array of ints

Code:

    int **array_of_years = malloc( 11* sizeof(**array_of_years));

The point of this is to give my 2d array of ints enough space to store a count for each month for the years 2000-2009.
I use calloc because I want the memory to have the value of 0 so I can just up the counts as I go.

Code:

       for(i = 0; i < counter1; i++)
     array_of_years[i] = calloc(10 , sizeof(**array_of_years));

I have the program print Hi, I'm alive to test it out. Anyways this works on Dev-C, but when I try to run this on gcc it gives me the corrupted double-linked list error.

Reading up on this it looks like I probably overlapped the memory or something along those lines? Not familiar with this error at all. Any help to fix this would be greatly appreciated.

I stripped a lot of my code out to try to find out the source of the problem which is why I think it's the code I've given above.

Anyways I'll post the rest of the code just to show you what I have.
Thanks

Also this must be dynamically allocated for the counts.

Code:

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


struct struct_of_months
{
       char months[20];
};


int main(void)
{
    FILE *fp;
    char buffer[50];
    int counter1 = 0;
    char *p;
    int i;
    struct struct_of_months *array_of_months = malloc (sizeof(*array_of_months));
    int **array_of_years = malloc( 11* sizeof(**array_of_years));

//Opens the first file and stores the months in array of structures
    if ( (fp = fopen("months.txt", "r" )) == NULL )
    {
    printf("Couldn't open file\n");
    exit(1); 
    }
    while(fgets(buffer, sizeof(buffer), fp))
    {
        if (counter1>0)
           array_of_months=realloc(array_of_months,(counter1+1)*sizeof(*array_of_months)); 
        if ((p = strchr(buffer, '\n')) != NULL)
           *p = '\0';
        strcpy(array_of_months[counter1].months, buffer);  
        counter1++;         
    }   
fclose( fp );

//Supposed to allocate enough memory for the 2d array.
       for(i = 0; i < counter1; i++)
        array_of_years[i] = calloc(10 , sizeof(**array_of_years));
          printf("Hi, I'm alive\n");
                                    
free(array_of_months);
free(array_of_years);
getchar();
return 0;
}

Oops I just changed that to...

Code:

    int **array_of_years = malloc(sizeof(**array_of_years));

I meant to have it simply initialize the 2d array. Not give 11 ints. Is that even the right way to initialize a 2d array of ints that I have to dynamically allocate?

The structure part is right. I just needed one structure initialized then while grabbing the file below I just reallocated more memory as I needed it. So I think that is correct.

But even with taking the 11 out it still gives me the same error. Could it be with how I initialize the 2d array_of_years? or how I use calloc on it? or free it?

because when I take this part out....

Code:

   	for(i = 0; i < counter1; i++)
     array_of_years[i] = calloc(10 , sizeof(**array_of_years));

The error isn't there anymore.
Leads me to believe I messed up somehow with the calloc.

Found out what the problem was.

2 problems actually

1.) i wasn't allocating enough memory for the array of years.
2.) I also wasn't freeing the memory of that array correctly. I put in a for loop to free the memory in the arrays, then I freed the arrays themselves.

Finally getting the hang of it

That was just the error I was getting...