understanding some source code - c

Question

gcc 4.7.2
c89
Hello,
I am reviewing someones source code, and I have come across this.
I have this declaration and definition that I don't understand what it does. I know that the static means that it will not be exported out of the file.
static SERVICE_STATUS_HANDLE g_win_status_handle = NULL;
Because it is set to NULL it looks like a pointer. SERVICE_STATUS_HANDLE isnt' defined anywhere else. Only this file.
It is being used like this, is this comparing if g_win_status_handle is equal to NULL after SERVICE_STATUS_HANDLE is casted to 0 or NULL:
if(g_win_status_handle == (SERVICE_STATUS_HANDLE)0) {
/* do something */
}
And like this:
if(!SetServiceStatus(g_win_status_handle, &g_win_status)) {
/* do something */
}
Many thanks if someone can shed some light on this.

Answer 1

i have made small program
#include<stdio.h>
static SERVICE_STATUS_HANDLE g_win_status_handle = NULL;
int main()
{
if(g_win_status_handle == (SERVICE_STATUS_HANDLE)0) {
printf("ksdfbhdejkfb");
}
return 0;
}
compiled on gcc (GCC) 4.5.1 20100924 (Red Hat 4.5.1-4)
with c89 flags, like
gcc -std=c89 temp.c
its giving error
temp.c:3:30: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘g_win_status_handle’
temp.c: In function ‘main’:
temp.c:6:4: error: ‘g_win_status_handle’ undeclared (first use in this function)
temp.c:6:4: note: each undeclared identifier is reported only once for each function it appears in
temp.c:6:28: error: ‘SERVICE_STATUS_HANDLE’ undeclared (first use in this function)
temp.c:6:50: error: expected ‘)’ before numeric constant
Here it is obvious that SERVICE_STATUS_HANDLE must be defined some where.. if not defined then how your code is going to even compile?
May be it will be defined in some header file..
Updated answer from comments
SERVICE_STATUS_HANDLE is defined in windows.h and its going to include.
http://msdn.microsoft.com/en-us/library/windows/desktop/aa383751%28v=vs.85%29.aspx