Question

I am trying to compile a program I wrote a few years ago that simulates mouse clicks and key strokes. I’ve reduced it to this minimal example:

#include "Windows.h"

int main(){
    INPUT foo;
    return 0;
}

It gives me this error:

C:\projects\clicker>g++ minimaltest.cpp
minimaltest.cpp: In function 'int main()':
minimaltest.cpp:4:2: error: 'INPUT' was not declared in this scope
minimaltest.cpp:4:8: error: expected ';' before 'foo'

MSDN’s page on INPUT says it’s defined in Windows.h, so I don’t know why it doesn’t recognize the type.

Another stackoverflow user had a similar problem here, but their solution, adding #define _WIN32_WINNT 0x0500, didn’t fix the errors.

I was able to build the program years ago on windows XP. Could it be that INPUT doesn’t work on Windows 7 the way it did on XP? Or maybe I forgot to supply a flag to the compiler?

Answer 1

You’ve misplaced your #define to after the #include. The result of this is that windows.h sees _WIN32_WINNT as undefined, so INPUT is not declared. Then you define it after INPUT‘s chance of existing has passed.

#define _WIN32_WINNT 0x0500 //RIGHT
#include "Windows.h"
#define _WIN32_WINNT 0x0500 //WRONG

int main(){
    INPUT foo;
    return 0;
}

As a side note, unless windows.h is in the same directory as the source file, it should typically be imported using #include <> rather than #include "".