Cannot found any data type used by SendInput() function

Question

I'm trying to use SendInput() function. I wrote this code:

#include <stdio.h> #include <stdlib.h> #include <windows.h> #include <winuser.h> #define WIN32_LEAN_AND_MEAN //... KEYBDINPUT kbi; kbi.wVk = 0x31; kbi.wScan = 0; kbi.dwFlags = 0; kbi.time = 0; INPUT input; input.type = INPUT_KEYBOARD; input.ki = kbi; SendInput(1, &input, sizeof input);

Compiling:

gcc -Wall -o window.exe win32.c -lWs2_32

I get:

win32.c: In function ‘main’: win32.c:13:2: error: ‘KEYBDINPUT’ undeclared (first use in this function) win32.c:13:2: note: each undeclared identifier is reported only once for each function it appears in win32.c:13:13: error: expected ‘;’ before ‘kbi’ win32.c:14:2: error: ‘kbi’ undeclared (first use in this function) win32.c:20:2: error: ‘INPUT’ undeclared (first use in this function) win32.c:20:8: error: expected ‘;’ before ‘input’ win32.c:21:2: error: ‘input’ undeclared (first use in this function) win32.c:21:15: error: ‘INPUT_KEYBOARD’ undeclared (first use in this function)

I have no idea how to fix tihis. According the documentation it's declared in Winuser.h header. But don't works for me.

You can check the header files if those structures have been declared under some macro, in which case you will have to pass that macro definition through command line using -D option or explicitly define it in your source — another.anon.coward
– another.anon.coward, Commented Jun 20, 2012 at 16:44

BrendanMcK · Accepted Answer · 2012-06-20 23:41:00Z

#define _WIN32_WINNT 0x0403 #include <windows.h>

Seems this is the magic #define you need somewhere in your project (either explicitly in code, or via compiler command line param -D).

Note that windows.h includes winuser.h, so there's no need to include that, as it's included already for you. Also, the WIN32_LEAN_AND_MEAN define only has any effect if it's included before windows. Details about what it does here; it's not needed or particularly useful these days.

--

So what's going on here? Looking for the definition of KBDINPUT in winuser.h (C:\Cygwin\usr\include\w32api\winuser.h), we see:

#if (_WIN32_WINNT >= 0x0403) typedef struct tagMOUSEINPUT { ... } MOUSEINPUT,*PMOUSEINPUT; typedef struct tagKEYBDINPUT { ...

That's the problem; these only get defined if _WIN32_WINNT is greater than 0x0403.

Those are the files from the cygwin package. Interestingly, the winuser.h from the Microsoft SDK (usually installed in C:\Program Files\Microsoft SDKs\Windows\v7.1\Include\WinUser.h) uses a different condition:

#if (_WIN32_WINNT > 0x0400)

...which explains Jay's suggestion - he's likely looking at the MS files, where 0x0401 would be sufficient here; and also explains why it's not working for you - you're likely using the cygwin ones with a higher version requirement. As to why these two files are different - I've no idea there...

Jay · Accepted Answer · 2012-06-20 16:49:18Z

I guess you need to add

#define _WIN32_WINNT 0x0401 #include <windows.h> #include <winuser.h>

before including windowsh and winuser.h in your source.

zar · Accepted Answer · 2017-09-27 18:07:38Z

This is an issue with older IDEs like VC6, I tried the above and it didn't work. I had to supply the flag on project settings.

Go to Setting >> C/C++ tab >> select 'General' from Catagory combo box add /D _WIN32_WINNT=0x401 to Project settings edit box. That's for VC6.

/d is how you supply the flag and the actual flag is _WIN32_WINNT=0x401. I do had to set it to 0x401, other values like 0x0500 were causing more errors.

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