#include<stdio.h>
//#include<stdlib.h> --> When this include is not commented out, after build, you will get Warning C4013 'malloc' undefined; assuming extern returning int. In Win10 64bit, this will cause bad malloc behaviour and crash due to access violation.

struct MyStruct{
  int a;
};

int main() {
  struct MyStruct *m = (struct MyStruct*)(malloc(sizeof(struct MyStruct)));
  m->a = 5; //will crash due to access violation at this line.
  printf("m->a = %d\nPress Enter...\n", m->a);
  getchar();
}