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<HTML><LINK HREF="style.css" REL="STYLESHEET" TYPE="text/css"><HEAD><TITLE>Win32 Tutorial - Solutions to Common Errors</TITLE></HEAD><BODY><FONT SIZE="-1">[ <A HREF="./index.html">contents</A>| <A HREF="http://www.winprog.org/">#winprog</A>]</FONT><HR><H1>Solutions to Common Errors</H1><UL> <LI><A HREF="#_main">Error LNK2001: unresolved external symbol _main</A> <LI><A HREF="#C2440">Error C2440: cannot convert from 'void*' to 'HICON__ *'</A> (or similar) <LI><A HREF="#RC1015">Fatal error RC1015: cannot open include file 'afxres.h'</A> <LI><A HREF="#LNK2001">Error LNK2001: unresolved external symbol InitCommonControls</A> <LI><A HREF="#Dialog">Dialog does not display when certain controls are added</A></UL><H2>Error <A NAME="_main">LNK2001</A>: unresolved external symbol _main</H2>An unresolved external occurs when some code has a call to a function in another moduleand the linker can't find that function in any of the modules or libraries that you arecurrently linking to.<P>In this specific case, it means one of two things. Either you are trying to write a Win32GUI application (or non-console application) and accidently compiled it as a Console application... or you really are trying to compile a console application and didn't write orproperly compile in a main() function.<P>Generally the first is the most common, if you specify Win32 Console as the project typein VC++ when you create your project you will get this error. You will also likely get itif you try to compile from the command line using BC++ but you neglect to specify the correct parameters to tell it to make a Win32 GUI application instead of a console appwhich is the default.<H3>Fixing</H3>If you're using VC++ re-create your project and select the Win32 Application project type(NOT "Console").<P>If you're using BC++ command line compiler, use -tW to specify a windows application.<H2>Error <A NAME="C2440">C2440</A>: cannot convert from 'void*' to 'HICON__ *' (or similar)</H2>If you're compiling the code from this tutorial, it means that you are trying to compile it as C++ code. The code is written for the bcc32 and VC++ C compilers, and as such may not compileexactly the same under C++ since C++ has much stricter rules about converting types. C willjust let it happen, C++ wants to you to make it explicit.<P>VC++ (and most compilers) will automatically compile a file with a .cpp extension as C++ code, anda file with a .c extension as C code. If you have added the tutorial code to a .cpp file, thisis the most likely reason of getting this error.<P>If you're compiling code not from this tutorial, I can't guarantee that it's correct and thereforit may actually be an error that needs resolving. You'll have to use your own judgement todetermine if it's safe to cast the value and remove the error, or if you are actually tryingto make a variable be something it's not.<H3>Fixing</H3>If you want to use C, simply rename your file from .cpp to .c. Otherwise, simply add a cast, all of the code in the tutorial will work without any other changes when compiled as C++.<P>For example, in C this will work:<P><PRE CLASS="SNIP"> HBITMAP hbmOldBuffer = SelectObject(hdcBuffer, hbmBuffer);</PRE><P>But in C++ requires a cast:<P><PRE CLASS="SNIP"> HBITMAP hbmOldBuffer = (HBITMAP)SelectObject(hdcBuffer, hbmBuffer);</PRE><H2>Fatal error <A NAME="RC1015">RC1015</A>: cannot open include file 'afxres.h'.</H2>Oddly enough, VC++ adds <CODE>afxres.h</CODE> to resource files even when you aren't using an MFC project, and yet the file may only be installed if you install MFC. This perticular file isn't actually required, so to fix the erroryou can edit the .rc file in notepad and replace both occurances of <CODE>"afxres.h" </CODE>with <CODE>"winres.h"</CODE> (note that there should be two of them, and you need to change both).<H2>Error <A NAME="LNK2001">LNK2001</A>: unresolved external symbol InitCommonControls</H2>You aren't linking to comctl32.lib which this API is defined in. This library is not included bydefault so you will either need to add it to the libraries on your command line, or add itin your VC++ project settings on the Link tab.<H2><A NAME="Dialog">Dialog</A> does not display when certain controls are added</H2>Controls such as the ListView, TreeView, Hotkey, Progress Bar, and others are classified as Common Controls,as they were added to windows in comctl32.dll and were not available prior to Windows 95. Controls suchas BUTTON, EDIT, LISTBOX, etc... while no doubt being common, are not "Common Controls" and I generallyrefer to them as "Standard Controls".<P>If you add a Common Control to a dialog and it fails to display, you most likely failed to call <CODE>InitCommonControls()</CODE>before running your dialog, or perhaps at all. The best place to call it is first thing in <CODE>WinMain()</CODE>. Callingit in <CODE>WM_INITDIALOG</CODE> is too late, since the dialog will fail before it reaches this point and it will neverget called.<P>Some people and documentation may tell you that <CODE>InitCommonControls()</CODE> is deprecated and you should use <CODE>InitCommonControlsEx()</CODE>.Feel free to do this if you want, <CODE>InitCommonControls()</CODE> is just simpler and there's nothing wrong with using it.<HR><FONT SIZE="-1">Copyright © 1998-2003, Brook Miles (<A HREF="mailto:forger(nospam)winprog.org">theForger</A>). 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