Function keeps overwriting previous structure data [closed] - c++

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when I enter data using my add function, I am able to print them no problem. Adding a vaule for start(x,y), end(x,y) works and I am able to print the values. But when I specify that I want two numGraphicElements when the function leaves after entering the first set of start and end values. It overwrites my previous values when going through the loop a second time.
When I print the values it for some reason overwrites my first values with random numbers and then only shows the second set of start(x,y) end(x,y) values.
example of first set: start(1,2) end (3,4)....this print properly
example of second set added: start(9,8) end (6,7)...this prints as well
example pf print out with 2 sets together, x(23424), y(653243), end = x(2334) y(33434).....x(9) y(8) end x(3) y(4).
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <crtdbg.h>
#define _CRTDBG_MAP_ALLOC
enum
{
RUNNING = 1
};
struct Point
{
int x, y;
};
struct Line
{
Point start;
Point end;
};
struct GraphicElement
{
enum
{
SIZE = 256
};
unsigned int numLines; //number of lines
Line* pLines; //plines points to start and end
char name[SIZE];
};
typedef struct
{
unsigned int numGraphicElements;
GraphicElement* pElements; //the head points to pLines
} VectorGraphic;
void InitVectorGraphic(VectorGraphic*);
void AddGraphicElement(VectorGraphic*);
void ReportVectorGraphic(VectorGraphic*);
VectorGraphic Image;
int main()
{
char response;
InitVectorGraphic(&Image);
//for debugging purposes
_CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);
//main menu for the program
while (RUNNING)
{
printf("\nPlease select an option:\n");
printf("1. Add a Graphic Element\n");
printf("2. List the Graphic Elements\n");
printf("q. Quit\n");
printf("CHOICE: ");
fflush(stdin);
scanf("%c", &response);
switch (response)
{
case '1':
AddGraphicElement(&Image);
break;
case '2':
ReportVectorGraphic(&Image);
break;
case 'q':
CleanUpVectorGraphic(&Image);
return 0;
default:
printf("Please enter a valid option\n");
}
printf("\n");
}
}
/*initialize the vectors, allocate memory*/
void InitVectorGraphic(VectorGraphic * pImage)
{ //addres of pImage is passed in
struct GraphicElement *pElements;
pImage->pElements = (GraphicElement*) malloc(sizeof(GraphicElement)); //pImage is now the addess of image
pElements = (GraphicElement*) malloc(sizeof(GraphicElement));
pImage->numGraphicElements = 8;
pImage->pElements = NULL;
}

Answer 1

Here
line = (struct Line *) malloc(sizeof(Line));
the code allocates exactly one line-object.
Here its seems to address more then just line[0]:
line[pImage->numGraphicElements]....
Doing so the code invokes undefined behaviour, anything can happen from this moment on. This includes overwriting other memory belonging to the same process.