Adding element to array, old values turns to 0 but new shows - c

Question

I have written this program where I can add pics to a staff using their names. but right now it adds the new value but the already existing values becomes 0.
this is the outcome:
type in the name you would like to add pic to
Anna
type in pic
55
1.Show existing
2.add pic to a staff
1
Adam 1,2,3,
Anna 0,0,0,55,
the rest of the code:
typedef struct Staff
{
char name[30];
int *pic;
int imagecount;
} Staff;
void printStaff(Staff *pStaff)
{
printf("%s ", pStaff->name);
if ( pStaff->pic) {
for(int i=0; i<pStaff->imagecount; i++){
printf("%d,",pStaff->pic[i]);
}
}
printf("\n");
}
void PrintList(Staff aLista[], int staffCount)
{
for (int i = 0; i < staffCount; i++) {
printStaff(&aLista[i]);
}
}
UPDATED CODE:
Staff addpic(Staff array[], int staffCount)
{
Staff newStaff = {};
printf("type in the name you would like to add pic to \n");
fgets(newStaff.name, 30, stdin);
for(int i = 0; i< staffCount; i++) {
if(strcmp(array[i].name,newStaff.name)==0) {
if(array[i].imagecount<5) {
printf("type in pic\n");
int newpic;
scanf("%d",&newpic);
array[i].imagecount++;
int *newpics = realloc(newStaff.pic, (array[i].imagecount) * sizeof(int));
newpics[array[i].imagecount-1] = newpic;
array[i].pic = newpics;
}
}
}
return newStaff;
the rest of the code:
int main(void)
{
int staffCount=0;
int input;
int test[3] = {1,2,3};
Staff myStaff[5] = { {"Adam", test, 3},{"Anna",test,3} };
staffCount=2;
do
{
printf("1.Show existing \n");
printf("2.add pic to a staff");
printf("\n");
scanf("%d", &input);
switch(input)
{
case 1:
PrintList(myStaff,staffCount);
break;
case 2:
addpic(myStaff,staffCount);
break;
default:
printf("inccorect inpput\n");
break;
}
}while (input<'1' ||input<'2');
return 0;
}
any help is appreciated, but I'm new to coding so keep that in mind.

Answer 1

In the addpic function you do
int *newpics = realloc(array[i].pic, ...);
One problem is that if you do it for one of the two elements you have initialized in array, then array[i].pic is pointing to the first element of an array (the array test in the main function).
Arrays can not be reallocated. If you want to reallocate the memory you need to allocate the original memory dynamically as well.

Answer 2

newStaff.pic is initialized to NULL and not updated then, so realloc(newStaff.pic, (array[i].imagecount) * sizeof(int)); is equivalent to malloc((array[i].imagecount) * sizeof(int));.
Elements allocated via malloc() and not initialized hae indeterminate value, and they happened to be zero in this case.
You can take over the contents by manually copying them.
int *newpics = realloc(newStaff.pic, (array[i].imagecount) * sizeof(int));
/* add this line to copy contents */
for (int j = 0; j < array[i].imagecount-1; j++) newpics[j] = array[i].img[j];
newpics[array[i].imagecount-1] = newpic;
Unfortunately, this method is not good because this may cause memory leak if addition like this to the same element of array is done multiple times.
Better way is to allocate the buffer to assign to img dynamically and pass them to realloc(). Then, realloc() will do the copying for you.
Initialization part:
int test[3] = {1,2,3};
Staff myStaff[5] = { {"Adam", test, 3},{"Anna",test,3} };
staffCount=2;
/* add this to change statically allocated arrays to dynamically allocated ones */
for (int i = 0; i < staffCOunt; i++) {
int* newpics = malloc(myStaff[i].imagecount * sizeof(int));
for (int j = 0; j < myStaff[i].imagecount; j++) newpics[j] = myStaff[i].img[j];
myStaff[i].img = newpics;
}
Updating part:
/* use array[i].pic instead of newStaff.pic */
int *newpics = realloc(array[i].pic, (array[i].imagecount) * sizeof(int));
/* then, no manual copying is required */
(error checkings are omitted)