程序中途终止

Question

i think terminates after the end of the stud()

struct stud
{
  int flag;
  char surname[90];
  int semester;
};


int prepush(int *stack,int *head,int *n)
{
 int c,r;
 int *p;
 printf("[1].Add Student\n");
 printf("[2].Add Proffesor\n");
 do
 {
    printf("Pick:");
    scanf("%d",&c); 
    getchar();
 }while(c!=1&&c!=2);
 switch(c)
 {
    case 1:p=stud();break;
    case 2:p=prof();break;
 }
 r=push(stack,&head,&n,p);
 return r;
}

i don't know what to return so i can put it in my stack..adress or what

int stud()
{
  struct stud a,*p;
  p=(void *)malloc(sizeof(a));
  p->flag=1;
  printf("Give surname:");
  gets(p->surname);
  printf("\nGive semester:")
  scanf("%d",p->semester);
  return p;
}

this is how i call it r=push(stack,&head,&n,p);

int push(int *stack,int *head,int *n,int *p)
{
  if(*head==*n)
    return 0;   
  stack[*head++]=p;
  return 1;
}

i actually want to put into a stack pointers that point to structs

Answer 1

The three following lines are a major problem:

struct stud a,*p;
p=(struct stud *)malloc(sizeof(a));
p=&a;

Here you declare two local variables a and p , allocate memory and make p point to it. You the directly afterward reassign p to point to the a variable. That means you loose the memory you allocated in the previous line, and have a memory leak.

What's worse is that you then return this pointer to a local variable, and as you know local variables goes out of scope once the function they were defined in returns. So what will the pointer then point to? Using this pointer leads to undefined behavior .