链表-细分错误

Question

This code is supposed to make a link list of ten names inputed by the user and it should print out that list.

#include<stdio.h>
#include<stdlib.h>
struct NameList
{
    char *name;
    struct NameList *nname;
};
typedef struct NameList NL;

int main()
{
    int i;
    NL *first;
    NL *next;
    first = (NL*)malloc(sizeof(NL));
    if (first ==NULL)
            printf("Memory not properly allocated\n");
    NL *pNames;
    pNames =  first;
    for(i = 0; i<10; i++)
    {
            printf("Enter a name: ");
            scanf("%s", &pNames->name);
            if(i == 9)
                    next = NULL;
            else
                    next = (NL*)malloc(sizeof(NL));
            pNames->nname = next;
            pNames = pNames->nname;
    }

Up to here there are no issues, I input the ten names but as soon as I enter the last name I get a segmentation fault. I'm guessing it's originating from here but I am not sure at all

        pNames = first;
        while(pNames != NULL)
        {
                printf("%s\n", pNames->name);
                pNames = pNames->nname;
        }


    }

Answer 1

This line is the source:

printf("Enter a name: ");
scanf("%s", &pNames->name);

Would be best to create a static buffer like this:

char buf[20];

then

printf("Enter a name: ");
scanf("%s", buf);

finally:

pNames->name = strdup(buf);

Edit: For sake of completeness, there is a risk of buffer overflow. where more than certain characters go past the end of the buffer inducing undefined behaviour. This can be mitigated as suggested by @ebyrob , in this fashion

fgets(buf, 20, stdin);

Answer 2

allocate space for "name", preferably use std::string

    you need to get "next" node.

      for(i = 0; i<10; i++)
            {
                    printf("Enter a name: ");
                    scanf("%s", &pNames->name);
                    if(i == 9)
                            next = NULL;
                    else
                            next = (NL*)malloc(sizeof(NL));
                    pNames->nname = next;
                    pNames = next;
            }

              pNames = first;
                while(pNames != NULL)
                {
                        printf("%s\n", pNames->name);
                        pNames = pNames->next;
                }

Answer 3

You have not allocated memory to hold the name field of your NameList objects. The name field is of type char * which has enough room for a pointer, not a string of characters. When you perform scanf(%s, &pNames->name); you are telling scanf to write the name into that memory location, but that will overwrite a lot more than the bytes needed to store a pointer.

Instead you could have scanf load into a temporary array first, then malloc enough space to hold it

char *tempbuff = malloc(128); // or some large enough buffer
for (i = 0; i<10; ++i) {
    // load the input into tempbuff first
    scanf("%s", tempbuff);
    // now make room for the string in the current object
    pNames->name = malloc(strlen(tempbuff)+1); // leave room for trailing null
    // now copy it from the tempbuff to its new home
    strcpy(pNames->name,tempbuff);
    .... // rest of code