Using the following struct:

typedef struct lista {
    int num;
    struct lista * sig;
} nodo;

We then have the following function to erase a linked list formed by the previous struct nodes:

void eliminarListaEntera(nodo * registro) {
    nodo * aux = NULL;
    
    while(registro->sig != NULL){
        aux=registro->sig;
        printf("Borrando nodo de la lista\n");
        free(registro);
        registro=aux;
    }
    free(registro);
    registro = NULL;
}

The issue I'm seeing: If I run the following inside main() before and after calling eliminarListaEntera:

printf("POINTER %p\n", (void *) primerNodo);

I get the same value. Shouldn't it be 0 (NULL) after calling the delete function?

If I try to traverse it again, I get only a random value like -159426562 which I guess it's because it's retrieving a garbage value from memory.

CodePudding user response：

When main calls eliminarListaEntera(primerNodo), it passes the value of primerNodo. Inside eliminarListaEntera, the parameter registro is a separate object and does not refer in any way to the primerNodo in main.

The statement registro = NULL; sets registro to NULL and has no effect on primerNodo in main.

If you want a called function to affect an object in the caller, you can pass a pointer to the object:

void eliminarListaEntera(nodo **p) {
    nodo *registro = *p;  // Copy the original pointer for ease of use.
    nodo * aux = NULL;
    
    while(registro->sig != NULL){
        aux=registro->sig;
        printf("Borrando nodo de la lista\n");
        free(registro);
        registro=aux;
    }
    free(registro);
    *p = NULL;  // Set the original pointer to NULL.
}

Then main can call this routine with eliminarListaEntera(&primerNodo);.