CHAPTER 21. STRUCTURES CHAPTER 21. STRUCTURES

Chapter 21

Structures

A C/C++ structure, with some assumptions, is just a set of variables, always stored in memory together, not necessary of the
same type^1.

21.1 MSVC: SYSTEMTIME example.

Let’s take the SYSTEMTIME^2 win32 structure that describes time.

This is how it’s defined:

Listing 21.1: WinBase.h

typedef struct _SYSTEMTIME {
WORD wYear;
WORD wMonth;
WORD wDayOfWeek;
WORD wDay;
WORD wHour;
WORD wMinute;
WORD wSecond;
WORD wMilliseconds;
} SYSTEMTIME, *PSYSTEMTIME;

Let’s write a C function to get the current time:

#include <windows.h>
#include <stdio.h>

void main()
{
SYSTEMTIME t;
GetSystemTime (&t);

printf ("%04d-%02d-%02d %02d:%02d:%02d\n",

t.wYear, t.wMonth, t.wDay,

t.wHour, t.wMinute, t.wSecond);

return;
};

We get (MSVC 2010):

Listing 21.2: MSVC 2010 /GS-

_t$ = -16 ; size = 16
_main PROC
push ebp
mov ebp, esp
sub esp, 16
lea eax, DWORD PTR _t$[ebp]

(^1) AKA“heterogeneous container”
(^2) MSDN: SYSTEMTIME structure