Bdtjtk

Getting the following warning message:

database.c:15:19: warning: assignment makes integer from pointer without a cast [-Wint-conversion]

  ptr->LastName[0] = NULL;

                   ^

database.c:16:26: warning: assignment makes integer from pointer without a cast [-Wint-conversion]

  ptr->FirstMiddleName[0] = NULL;



                      ^

I tried using pointers a few different ways but I don't understand them very well and can't figure out how to avoid this.

#include <stdio.h>



int main() {

        struct employee {

                char LastName[30];

                char FirstMiddleName[35];

                float Salary;

                int YearHired;

        };



        struct employee employees[20];

        struct employee *ptr, person;

        ptr = &person;



        ptr->LastName[0] = NULL;

        ptr->FirstMiddleName[0] = NULL;

        ptr->Salary = -1;

        ptr->YearHired = -1;



        printf("%i", person.YearHired);

        printf("%s", person.LastName[0]);



        for(int i = 0; i < 20; i++) {

                employees[i] = person;

                //printf("%in", i);

        }



        printf("%c", employees[3].LastName[0]);

}

I would like to initialize an array of 20 "employees" with the initial values such that numerical values are set to -1, and the strings contain the null character as the zeroth character.
Instead I get the above warning, and if I replace the NULL assignment with a letter it says "Segmentation fault (core dumped)".

NULL is a null pointer constant, not the null character. Use:

ptr->LastName[0] = '';

Compiler warning message is clear enough to tell what you are doing the wrong. Here

ptr->LastName[0]  = NULL; /* NULL is equivalent of (void*)0 not  */

LastName[0] is character not character pointer. You might want

ptr->LastName[0]  = ''; /* now here  and Lastname[0] both are of char type */

NULL is a pointer constant, and you're trying to assign that to an element of the LastName or FirstMiddleName fields. Instead, assign 0 to the first character of each, which makes them empty strings.

    ptr->LastName[0] = 0;

    ptr->FirstMiddleName[0] = 0;

This also isn't valid:

printf("%s", person.LastName[0]);

Because person.LastName[0] is a single character, not a string. You instead want:

printf("%s", person.LastName);

To fix the warning replace NULL with the null character ''. NULL is a pointer, not what you want.

ptr->LastName[0] = '';

To fix the segmentation fault replace person.LastName[0] with person.LastName in your printf. person.LastName[0] is a single character. printf %s expects the address of a null-terminated string.

printf("%s", person.LastName);

That printf statement may still fail if you don't put a null termination somewhere in your string:

 ptr->LastName[0] = 'a';   //may still fail in printf without termination.

vs

ptr->LastName[0] = 'a';   

ptr->LastName[1] = '';  

The macro NULL is an invalid pointer not the ASCII NUL character, you should not use it as a character constant. The NUL character is :

    ptr->LastName[0] = `` ;

    ptr->FirstMiddleName[0] = `` ;

Or it is also valid to simply use a literal zero:

    ptr->LastName[0] = 0 ;

    ptr->FirstMiddleName[0] = 0 ;