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If you used the application wizard to start your application building, and you specified that you were building an MFC application... then you should already have a CWinApp derived class somewhere in your project. Don't redefine the call, just call it from somewhere in there (if you redefine you'll override the original call).
And you can only the CAux::SetRegistryKey(); method without initializing an object if the call is static (something you don't want to do anyway).
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Thanks, Albert,
You are completely right and it was my fault. Indeed, my application has a CwinApp derived class which is called CPatchApp:
class CPatchApp : public CWinApp
{
public:
CPatchApp();
...
}
All I had to do then is to declare
(CPatchApp *) pApp = AfxGetApp();
and to use that pApp pointer to access protected SetRegistryKey function like:
pApp->SetRegistryKey( LPCTSTR lpszRegistryKey );
Instead I wrote
(CWinApp *) pApp = AfxGetApp();
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Sorry, it doesn't work either.
I do have a CWinApp derived class in my project (refer to my previous reply).
It is a simple dialog application. I need to write to the registry some value
and -- before using WriteProfileString -- I try to call SetRegistryKey.
There is the code snippet:
AfxGetApp()->SetRegistryKey(lpszRegistryKey);
At compiling I got the following message:
patchdlg.cpp(229) : error C2248: 'SetRegistryKey' : cannot access protected member declared in class 'CWinApp'
which returns us to the beginning of the discussion.
Is it possible to avoid that error at all? What is it there that I have overlooked?
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Where are you making that call from? You have to make it from within the CWinApp derived class (since it is protected).
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Hi, Albert,
I'd tried various approaches until I found an excellent C++ Tutorial (http://www.learncpp.com/) and got the understanding that my problem is related to the inheritance subject. As it is clearly stated in the tutorial:
2. The protected access specifier allows derived classes to directly access members of the base class while not exposing those members to the public.
I see now that I have to make call within but my derived class. It does work except that there reveals another problem -- WriteRegisterString needs an access to the m_pszRegistryKey variable which is an attribute of CWinApp class. IAE, I have to learn a bit more on the subject.
The discussion was very helpful and I thank you for the time you spent on it.
Regards,
Anatoly
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Trying to convert a very old C program to Microsoft Visual Studio 2010. After some warnings, including some extern "C"'s and all that, everyting compiles. However, the linker keeps calling that is misses an external symbol "_VERSION". I have been looking through all code and can't find any reference to it. I included a char * _VERSION somewhere in my main source (within and outside the extern "C") Still complains.
Does anyone have an idea how I could find out where the linker finds the call of this reference? Is there som option that can persuade the linker to provide me with much more information or something like that?
This is getting extremely frustrating, since everything else seems to work as expected. Just this @!$@! _VERSION....
Thanks in advance.
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Did you try doing a solution wide search for _VERSION?
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Well, the point is that the software calls some other C modules. I did scan all sources for as far as I can see, but they are not all included in the VS2010 solution so I had to so that by hand. However, I would have expected to at least get rid of the linker's complaint by adding a variable _VERSION in my own source code. Possibly with a wrong type, but then I would expect another complaint from Microsoft somewhere....
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well when you get an unresolved external symbol, its because something in your code is referencing it.. either directly or one of your headers is referencing it...
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How did you add the char* _VERSION?
And how and where is it used in your code?
Considering that the linker is complaining I'm guessing you added something like:
char* _VERSION;
Somewhere in a source file?
The solution is to make it something like:
char* _VERSION = "1.0"
And add that to a source file.
But what the actual type and contents have to be totally depends on what the original code intended with it.
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Yes, I tried that too (adding char *_VERSION = "x.x"; as a global variable) but it does not help a bit
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By the way, if you don't know, the Studio search will work in any directory you ask it to. So you can search for a line of code through all your libraries and includes.
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I fully agree with you all. Point however is that I need to find-out where my code is using it anbd even more: when I simply introduce a global variable _VERSION, I would no longer expect an "unresolved external" for _VERSION.
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...that's partially true... did the _VERSION name have name mangling (or decoration), if so, you must match the name exactly, including the mangling (in case its actually a structure name or such)...
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Well you do have a point there. The linker complains about a straight _VERSION. As far as I know, it would complain about something including the name mangling normally. It does however mean that - if I introduce a variable named _VERSION - that will probably be called differently internally. I have been looking into a way to remove the name mangling from a particular variable, but have not yet found anything.
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the extern C removes name mangling... so there may be some definition that you need to wrap with that somewhere in your source... you just have to find it (on a related note, wish linkers gave better error information, lol)
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I didn't realise from the original post that the name _VERSION was the name given by the linker, and is mangled.
The unmangled name is VERSION, so that's what we're looking for here. Also, see my other post.
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Good point, did you try:
char* VERSION = "1.0"
Or else, if above does not work:
extern "C" char* VERSION = "1.0"
Also, before you do this you really ought to use the search in files function to find out where VERSION (without the underscore) is being used and for what.
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William Engberts wrote: ...I need to find-out where my code is using it...
Doesn't the linker tell you this?
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"Some people are making such thorough preparation for rainy days that they aren't enjoying today's sunshine." - William Feather
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Can't remember off the top of my head, but I don't think it does... remember that the linker works with the compiler output... so it doesn't necessarily have an association between an unfound object and where it was referenced in source (although it may, this is more of a linker design feature).
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What is the exact message that the Linker produces?
The best things in life are not things.
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This is the exact message: "error LNK2001: unresolved external symbol _VERSION"
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This means that you have a statement of the form:
extern "C" <some type> VERSION;
and a reference to the variable VERSION somewhere in your final program. However, if this is not anywhere in your source modules it could possibly be in an associated library, so you may need to check what external libraries are being added to your program.
You could also try the /MAP and/or /VERBOSE linker options to see if you can narrow it down to the actual module where it occurs.
The best things in life are not things.
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good tip about the linker options to play with... 
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One of the most common questions I ask myself is: "What tools can I use to help me find this bug in my code?" 
The best things in life are not things.
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