Thread: Can someone help me?

I know there is a problem in realloc but I don't know why

Code:

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


struct mystruct
{
    int valore;
    struct mystruct *next;
};
typedef struct mystruct Struct;


void crea_lista(Struct *mystruct, int *dim);
void modifica_lista();
void elimina_lista();
void aggiugni_lista();


int main()
{
    int i,dim=0;
    Struct *strutture;


    for(i=0;i<2;i++)
        crea_lista(strutture,&dim);


    return 0;
}


void crea_lista(Struct *mystruct, int *dim)
{
    int newdim=*dim+1;


    printf("%d - ",newdim);


    if(newdim==1)
        mystruct=malloc(newdim*sizeof(Struct));
    else
        mystruct=realloc(mystruct,newdim*sizeof(Struct));


    *dim=newdim;


    printf("%d\n",sizeof(mystruct));


}

Do you realize that you're passing that pointer into the crea_lista() function by value? Which means that any changes to the pointer is lost when the function returns.

So, please, how can I resolve it?

Try passing the pointer by reference.:

Code:

void crea_lista(Struct **mystruct, int *dim);
...
    for(i=0;i<2;i++)
        crea_lista(&strutture, &dim);
...

You'll also need to modify the function to properly reference the pointer.

thank you very much