Use After Free (UAF). Operating upon a memory pointer after it has been freed up is obviously a bug, causing UB. The pointer is sometimes called a dangling pointer. Here is a quick test case:
/* test case 8 : UAF (use-after-free) test case */static void uaf(void){ char *arr, *next; char name[]="Hands-on Linux Sys Prg"; int n=512; arr = malloc(n); if (!arr) FATAL("malloc failed\n"); memset(arr, 'a', n); arr[n-1]='\0'; printf("%s():%d: arr = %p:%.*s\n", __FUNCTION__, __LINE__, arr, 32, arr); next = malloc(n); if (!next) { free(arr); FATAL("malloc failed\n"); } free(arr); strncpy(arr, name, strlen(name)); /* Bug: UAF */ printf("%s():%d: arr = %p:%.*s\n", __FUNCTION__, __LINE__, arr, 32, arr); free(next);}
Again, neither at compile-time ...
