Question

The following code is taken from here. I removed all Windows NT part as I am working on Windows 7.

I copied this code and run in visual studio 2010 (New project-> VC++->CLR->CLR Console… ). But it is giving lots of unresolved extern ‘c’ errors as listed below the code. What wrong I have committed?

#define STRICT  1 

#include <windows.h>
#include <iostream>
using namespace std;

BOOL CALLBACK EnumWindowsProc(HWND hWnd, LPARAM lParam) {
DWORD dwThreadId, dwProcessId;
HINSTANCE hInstance;
char String[255];
HANDLE hProcess;
if (!hWnd)
return TRUE;        // Not a window
if (!::IsWindowVisible(hWnd))
return TRUE;        // Not visible
if (!SendMessage(hWnd, WM_GETTEXT, sizeof(String), (LPARAM)String))
return TRUE;        // No window title
hInstance = (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE);
dwThreadId = GetWindowThreadProcessId(hWnd, &dwProcessId);
hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, dwProcessId);
cout << hWnd << ' ' << dwProcessId << '\t' << String << '\t';
cout << "(None)\n";
CloseHandle(hProcess);
return TRUE;
}

int main(int argc, char *argv[], char *envp[]) {
EnumWindows(EnumWindowsProc, NULL);
return 0;
}

This is giving following Errors(and other similar unresolved extern C errors)

 1>wndowfind.obj : error LNK2028: unresolved token (0A000342) "extern "C" int __stdcall       
 EnumWindows(int (__stdcall*)(struct HWND__ *,long),long)"     3
 (?EnumWindows@@$$J18YGHP6GHPAUHWND__@@J@ZJ@Z) referenced in function "int __cdecl 
 main(int,char * * const,char * * const)" (?main@@$$HYAHHQAPAD0@Z)

 1>wndowfind.obj : error LNK2028: unresolved token (0A000346) "extern "C" unsigned long  
 __stdcall GetWindowThreadProcessId(struct HWND__ *,unsigned long *)"    
 (?GetWindowThreadProcessId@@$$J18YGKPAUHWND__@@PAK@Z) referenced in function "int __stdcall 
 EnumWindowsProc(struct HWND__ *,long)" (?EnumWindowsProc@@$$FYGHPAUHWND__@@J@Z)

 1>wndowfind.obj : error LNK2028: unresolved token (0A000347) "extern "C" long __stdcall 
 GetWindowLongW(struct HWND__ *,int)" (?GetWindowLongW@@$$J18YGJPAUHWND__@@H@Z) referenced in 
 function "int __stdcall EnumWindowsProc(struct HWND__ *,long)" 
 (?EnumWindowsProc@@$$FYGHPAUHWND__@@J@Z)

 1>wndowfind.obj : error LNK2019: unresolved external symbol "extern "C" int __stdcall  
 EnumWindows(int (__stdcall*)(struct HWND__ *,long),long)" 
 (?EnumWindows@@$$J18YGHP6GHPAUHWND__@@J@ZJ@Z) referenced in function "int __cdecl 
 main(int,char * * const,char * * const)" (?main@@$$HYAHHQAPAD0@Z)

 1>c:\users\afnan\documents\visual studio 2010\Projects\wndowfind\Debug\wndowfind.exe : fatal 
 error LNK1120: 10 unresolved externals
 1>
 1>Build FAILED.

UPDATED

By including the libraries (as suggested in the answers), I was able to run the program successfully. But I am not able to understand why only first character of string is printing not the complete one, as can be seen in the output:

00010060 2652   S       (None)
002502B2 5820   C       (None)
00090402 5160   w       (None)
00050392 5160   w       (None)
00060292 3520   F       (None)
000C02BA 3520   M       (None)
0001021A 3736   E       (None)
00040018 896    I       (None)
00010170 3580   A       (None)
0002003E 2684   D       (None)
00030316 4956   N       (None)
000202DE 3736   D       (None)
0001031E 2652   S       (None)
000100EA 2652   P       (None) 

In the output above, S is actually “start”, C is “console” etc I confirmed through spy++ tool.
How can I print the complete string instead of just first character?

Answer 1

CLR projects by default do not include the standard Windows libraries, such as user32.lib.

Edit your project properties, find the Linker Inputs option, and add kernel32.lib user32.lib advapi32.lib which are the usual libraries needed by Win32 code.