INITCOMMONCONTROLSEX was not declared in this scope - c

Question

When I compile
#include<windows.h>
#include <commctrl.h>
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
INITCOMMONCONTROLSEX ex;
return 0;
}
with
g++ 1.cpp -w -g -lgdi32 -lcomctl32 -o 1.exe
I get the error
1.cpp: In function 'int WinMain(HINSTANCE, HINSTANCE, LPSTR, int)':
1.cpp:8:2: error: 'INITCOMMONCONTROLSEX' was not declared in this scope
INITCOMMONCONTROLSEX ex;
^.
I suspect I am getting this error because in commctrl.h, following #if condition is not true.
#if (_WIN32_IE >= 0x0300)
typedef struct tagINITCOMMONCONTROLSEX {
DWORD dwSize;
DWORD dwICC;
} INITCOMMONCONTROLSEX,*LPINITCOMMONCONTROLSEX;
#endif
I tried compiling
#define _WIN32_IE 0x0300
#include<windows.h>
#include <commctrl.h>
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
INITCOMMONCONTROLSEX ex;
return 0;
}
and this works fine, I don't get any errors. I looked up MSDN but there's nothing written about adding #define _WIN32_IE 0x0300 there.
Questions :
What is the purpose of _WIN32_IE ?
Do I really need to hardcode its value when MSDN writes nothing about doing so ?

Answer 1

The initial version of comctl32 shipped with Windows 95/Windows NT. From then on each release up to Windows 7 got a new updated version but these new versions first shipped as part of Internet Explorer. Internet Explorer 3, 4, 5, 6 and 7 usually included new versions of comctl32, shlwapi and shell32.
This is mostly ancient history these days but you still need to declare which version of Windows and IE you are targeting to unlock certain features.
Adding #define _WIN32_IE 0x0300 to your code unlocks the features introduced in IE 3.0 and your program will only run on Windows 95 ORS 2 or later, Windows 95 RTM will need IE3 or 4 to be installed.
You don't care about Windows 95 (hopefully) but the same type of #if check applies to many other newer features as well and not all of them are correctly documented on MSDN because they probably assume that you are using a Visual Studio project that is less than 20 years old.
Unfortunately the minimum OS version listed on MSDN is wrong and cannot be trusted. Microsoft has removed 99% of the information about versions before 2000 and they seem to ignore anything before 2003/Vista these days.

Answer 2

What is the purpose of _WIN32_IE?
The extended common controls library shipped with Internet Explorer before it became a standard part of Windows. If you set the macros to tell the SDK which version of Windows you're targeting, then the SDK will probably set the IE version for you.
The fact that you had to do this for functionality this old suggests that you're using an old version of Visual Studio and/or the SDK. You might want to consider updating.
Note that, for these common controls, you probably also want to make sure you enable Windows Visual Styles.
Do I really need to hardcode its value when MSDN writes nothing about doing so?
You should set WINVER and _WIN32_WINNT per the MSDN guidelines. Depending on the version of Visual Studio you have, you might be able to set it with a project property. You can also do it with the /D option on the compiler command line, or in a header file that's included before any Windows headers. If you use a pre-compiled header, you could do it at the top of that file.