malloc(): corrupted top size when adding an element to a dynamic list-CodePudding

I am writing a dynamic list.
Here is the header file that contains the dynamic list and the function that add an element to the list.

#if !defined(STRING_LIST)
#define STRING_LIST

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

typedef struct string_list      
{
    char **list;
    int size;

    void (*add)(struct string_list *list, char *string);
} string_list;

void add(string_list *list, char *string)
{
    int old_size = list->size;
    list->size  = 1;
    char **new_list = malloc(list->size);

    if(!new_list)
    {
        puts("Error in malloc()");
    }

    for(int i = 0; i < old_size; i  )    // assigning the elements from the old array to the new array
        new_list[i] = list->list[i];

    if (list->list != NULL)
        free(list->list);
    
    list->list = new_list;
    list->list[list->size - 1] = strdup(string);
}

string_list *string_list_construct()
{
    string_list *list = malloc(sizeof(string_list));
    list->size = 0;
    list->list = NULL;

    list->add = add;
}

void string_list_deconstruct(string_list *list)
{
    for(int i = 0; i < list->size; i  )
    {
        printf("i:%i\n", i);
        free(list->list[i]);
    }

    free(list->list);
    free(list);
}
#endif

And here is the main function

#include <stdio.h>
#include "string_list.h"

int main()
{
    string_list *list = string_list_construct();

    for(int i = 0; i < 5; i  )
    {
        list->add(list, "item");
        printf("new size: %i\n\n", list->size);
    }
    string_list_deconstruct(list);
    return 0;
}

The dynamic list is a struct that has two data fields and one function pointer which points to add function below.

And when running the code I get

new size: 1

new size: 2

new size: 3

new size: 4

malloc(): corrupted top size
Aborted

I used valgrind to chick for memory leak but I found nothing.

Any help?

CodePudding user response：

you need to differentiate between the size and the length of an array and you can use realloc() if you want to expand an array.

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

char *strdup(const char *src) {
    char *dst = malloc(strlen (src)   1);  
    if (dst == NULL) return NULL;          
    
    return strcpy(dst, src);                      
                                
}


typedef struct string_list      
{
    char **list;
    unsigned int length;
    size_t size;

    void (*add)(struct string_list *list, char *string);
} string_list;

void add(string_list *stringlist, char *string)
{
  int old_size = stringlist->size;
  stringlist->length  = 1;
  stringlist->size  = sizeof(char*);
  
  stringlist->list = realloc( stringlist->list, sizeof( char* ) * stringlist->length );
  if(!stringlist->list)
  {
    puts("Error in realloc()");
    exit(1);
  }
  

  stringlist->list[stringlist->length-1 ] = strdup(string);
}

string_list *string_list_construct()
{
    string_list *list = malloc(sizeof(string_list));
    list->size = 0;
    list->list = NULL;

    list->add = add;

    return list;
}

void string_list_deconstruct(string_list *list)
{
    for(int i = 0; i < list->length; i  )
    {
        printf("free() i-th entry:%d\n", i);
        free(list->list[i]);
    }

    free(list->list);
    free(list);
}


int main()
{
    string_list *list = string_list_construct();

    for(int i = 0; i < 5; i  )
    {
        list->add(list, "item");
        printf("new length: %d\n", list->length);
        printf("new size: %ld\n\n", list->size );
    }
    string_list_deconstruct(list);
    return 0;
}