error: 'WlanScan' was not declared in this scope

Question

I have been playing around with wlanapi in windows. I did not have any problem compiling or running until I tried using the function WlanScan. Then I was unable to compile due to "WlanScan" not being declared in the scope. I wrote a really short program illustrating this using two functions: WlanOpenHandle that works and WlanScan which doesn't.

#include <windows.h>
#include <wlanapi.h>

int main()
{
    HANDLE hClient;
    WlanOpenHandle(2, 0, 0, &hClient);

    WlanScan(hClient, 0, 0, 0, 0);
}

Compiling that single file like this:

g++ main.cpp -lwlanapi

Results in this error:

main.cpp: In function 'int main()':
main.cpp:9:30: error: 'WlanScan' was not declared in this scope
  WlanScan(hClient, 0, 0, 0, 0);
                              ^

What could be the cause of this? I've been able to use a handful of functions from the wlanapi. I am on Windows 7 compiling with minGW.

EDIT: In accordance to what u/ IInspectable said, I changed the command used to compile to:

g++ -D_WIN32_WINNT=_WIN32_WINNT_WIN7 main.cpp -lwlanapi

And it worked!

@ThomasMatthews True, but that's for the next question -- don't get ahead of yourself. :) — Forest Kunecke, Aug 15 '14 at 20:01
@FKunecke What do you mean? This is c++, the compiler takes care of that — EFTH, Aug 15 '14 at 20:03
You declared the `main()` function as returning an `int`. Where does you code satisfy the declaration? Ideally, you should specify the return value to the operating system rather than relying on compilers. — Thomas Matthews, Aug 15 '14 at 20:05
@ThomasMatthews That may be true. But it is irrelevant to my question. — EFTH, Aug 15 '14 at 20:09
@EFTH I updated my answer; I'm curious though -- try just adding `#pragma comment(lib, "wlanapi.lib")` to your current code and see what happens. — Forest Kunecke, Aug 15 '14 at 20:10
@FKunecke Thank you for the help. But adding that line did not help. — EFTH, Aug 15 '14 at 20:13
@EFTH did it give you the same error? I'm not able to reproduce your problem. — Forest Kunecke, Aug 15 '14 at 20:14
@FKunecke Yeah, same error. I've looked around in my machine and been able to find two wlanapi.h files so far, both of which declare the function — EFTH, Aug 15 '14 at 20:25
@ThomasMatthews : it should, but doesn't need to (implicit `return 0`) — quantdev, Aug 15 '14 at 20:38
@ThomasMatthews: [What should main() return in C and C++?](http://stackoverflow.com/a/204483/1889329) — IInspectable, Aug 16 '14 at 12:38
Make sure the preprocessor symbol `_WIN32_WINNT` is set to `_WIN32_WINNT_WINXP` (or higher, e.g. `_WIN32_WINNT_VISTA`, `_WIN32_WINNT_WIN7`). The symbol must be defined prior to including the `` header file. It's recommended to pass it on the compiler's command line. — IInspectable, Aug 16 '14 at 12:47
@IInspectable Thank you! That worked. I updated the question to include this solution. If you put this in a real answer I can mark this question done and dealt with. — EFTH, Aug 17 '14 at 07:51

score 0 · Answer 1 · edited May 23 '17 at 10:33

It looks like someone else has had this problem before:

How To Compile C++ Code that has a 'wlanapi.h' and 'windows.h' dependency

The recommended solution is to just put it into Visual Studio and compile it using that; MinGW probably isn't able to find the library.

Using VS2010 I created a VC++ console application (with a precompiled header), and I was able to get the following to compile without any errors:

// wlanapi_Test.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"


int _tmain(int argc, _TCHAR* argv[])
{
    HANDLE hClient;
    WlanOpenHandle(2, 0, 0, &hClient);

    WlanScan(hClient, 0, 0, 0, 0);

}

And here's my precompiled header:

// stdafx.h : include file for standard system include files,
// or project specific include files that are used frequently, but
// are changed infrequently
//

#pragma once

#include "targetver.h"

#include <stdio.h>
#include <tchar.h>



// TODO: reference additional headers your program requires here


#include <windows.h>
#include <wlanapi.h>

#pragma comment(lib, "wlanapi.lib")

The magic happens inside `"targetver.h"`. If you don't provide this file (which Visual Studio generated for you automatically), it does nothing to help answer the question. In addition, the question states a **compiler** error (vs. a **linker** error), so this has nothing to do with not finding a library. — IInspectable, Aug 16 '14 at 13:02

error: 'WlanScan' was not declared in this scope

1 Answers1