Adding and listing an array of structs - c++

Question

I've been having a few problems with using an array of structs and simply listing them and adding to them. I am not really all too sure about what's happening, I've had a search around and asked a few friends and they've suggested that it is something to do with the memory allocation and another has said that memory allocation is not needed and that there is a problem in my code.
I have been unable to locate the problem and was wondering if anyone would be able to point me in the direction of to where I am going wrong.
I apologies if the code doesn't look right - not really sure on how to implement it on the site.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct data{
int testone;
int testtwo;
}data;
struct data _dataStore[25];
int dataCount = 0;
int addData(struct data __dataStore[dataCount]){
printf("\n\t\t\tPacket Source - ");
scanf("%i", &_dataStore[dataCount].testone);
printf("\t\t\tPacket Destination - ");
scanf("%i", &_dataStore[dataCount].testtwo);
system("CLS");
return 0;
}
void listData(struct data _dataStore[25]){
int i = 0;
for (i = 0; i < dataCount; i++){
printf("data stored - %i",dataCount);
printf("%i___%i \n", _dataStore[dataCount].testone,_dataStore[dataCount].testtwo);
}
}
int main(){
char choice;
do{
printf("\t\t\t Counter - %i", dataCount+1);
printf("\n\t\t\t1 - Add data. \n");
printf("\t\t\t2 - List data. \n");
printf("\n\t\t\tEnter your choice - ");
fflush(stdin);
choice = getchar();
getchar();
switch(choice){
case '1':
addData(&_dataStore[dataCount]);
dataCount++;
system("CLS");
break;
case '2':
system("CLS");
listData(&_dataStore[dataCount]);
break;
default:
printf("Invalid input \n");
break;
}
}while (choice != '5');
return 0;
}

Answer 1

There are quite a few apparent bugs, for example:
for (i = 0; i < dataCount; i++){
printf("data stored - %i",dataCount);
printf("%i___%i \n", _dataStore[dataCount].testone,_dataStore[dataCount].testtwo);
}
}
I suspect you wanted to say _dataStore[i] instead. Also, I suggest using a more sensible function prototype:
int addData(struct data* __dataStore, int arrayLen)

Answer 2

Here is the corrected code which works well for me:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct data{
int testone;
int testtwo;
}data;
struct data _dataStore[25];
int dataCount = 0;
int addData(){
printf("\n\t\t\tPacket Source - ");
scanf("%d", &_dataStore[dataCount].testone);
printf("\t\t\tPacket Destination - ");
scanf("%d", &_dataStore[dataCount].testtwo);
system("CLS");
return 0;
}
void listData(){
int i = 0;
for (i = 0; i < dataCount; i++){
printf("data stored - %d: ",dataCount);
printf("%d___%d \n", _dataStore[i].testone,_dataStore[i].testtwo);
}
}
int main()
{
char choice;
do{
printf("\t\t\t Counter - %i", dataCount+1);
printf("\n\t\t\t1 - Add data. \n");
printf("\t\t\t2 - List data. \n");
printf("\n\t\t\tEnter your choice - ");
fflush(stdin);
choice = getchar();
getchar();
switch(choice){
case '1':
addData();
dataCount++;
system("CLS");
break;
case '2':
system("CLS");
listData();
break;
case '5':
printf("Will exit...");
break;
default:
printf("Invalid input \n");
break;
}
}while (choice != '5');
return 0;
}
Please pay attention to the following: read / write integers with %d not %i, the index in listData() shall be i not dataCount, I removed the not-needed params of the functions since the variables are global, I added a new case in switch() so that it prints a better message when exiting, not "invalid input".
All variables you are using are statically allocated so you do not need memory allocation.