array of pointers to structures

Question

I'm trying to understand if my code is correct. I need to declare an array of pointers to structs, create a new struct and assign the values and print them. It seems to me that I'm not declaring array of pointers correctly. I need to know what I'm doing wrong. Thank you I'm getting this compile error: error: 'people' undeclared (first use in this function) And I've tried to insert struct data *list; into main but it wouldnt work

     char *book[] = { "x", "y", "z",};
     int number[] = { 1, 2, 3};

     struct data = { char *bookname; int booknumber;};

     function(char *x, int y)
     {
       static int count;

       struct data *list[3];

       //creating a new struct 
       list[count] = (struct data*) malloc( sizeof(struct data) );

       //assigning arguments
       list->bookname = x;
       list->booknumber = y;

       count++;
     }

     int main()
     {
       struct data *list[3];

       int i;
       for(i = 0; i < 3; i++)
       {
         function(book[i], number[i]);

         printf("name: %c number: %d", list[i]->bookname, list[i]->booknumber);
       }

Solution 1

Please change the following piece of code

    // declaring array of pointers to structs //         
     struct data *list;         
    //not compiling        
    //struct data *list[3]; ---> There is no problem with this statement.        
   //creating a new struct         
   list = (struct data*) malloc( sizeof(struct data) );  ---> //This statement should compilation error due to declaration of struct data *list[3]

to

struct data *list[100]; //Declare a array of pointer to structures  
//allocate memory for each element in the array
list[count] = (struct data*) malloc( sizeof(struct data) ); 

Solution 2

Since you want arrays, you need to declare arrays:

char *book[] = { "x", "y", "z",};
int number[] = { 1, 2, 3};

---

Another issue is

list = (struct data*) malloc( sizeof(struct data) );

//assigning arguments
list[count]->bookname = ...

Here, list is always going to have exactly one element. So if count is anything other than 0, you will be accessing an array out of bounds!

Comments

[Jack Morton]

off course, i just mistyped it. i ahve arrays in my actual program

[Jack Morton]

well, i have tried doing struct data *list[3]; but it wouldnt compile

[chrisaycock]

@JackMorton Make it a dynamic array: malloc( sizeof(struct data) * 3 )

[Jack Morton]

I'm sorry, 1st one is just a mistype again for me. it's in proper shape in the actual code

[Kevin Vermeer]

The [100] limit is a regression. This should also be dynamically allocated, or handled by the caller.

[Jay]

@Kevin, The answer is just a sample. So, I have used 100. I have just given him a pointer as to what was causing him the so called compilation error. Hope this clears the air.