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From "Reynolds, John" <John.Reyno...@flightman.com>
Subject RE: link error in release mode with Visual Studio 2008
Date Fri, 07 May 2010 16:19:04 GMT
That should be a static lib only results in a lib, duh!

From: Reynolds, John [mailto:John.Reynolds@flightman.com]
Sent: 07 May 2010 17:16
To: Log4CXX User
Subject: RE: link error in release mode with Visual Studio 2008

I suggest building the log4cxx.dll via ant as you only have do it once ( twice if you want
a release and debug version ) and you can set the correct paths to the dll and header files
in the VS project setting for your client project build configuration. Personally I very rarely
use application VS, just the command line.

First you need ant ( hence you need java ) and the cpptasks jar, see the first option  http://logging.apache.org/log4cxx/building/ant.html
(packaged APR and APR-Util, it builds in static versions of these into the dll ). The resultant
dll should be in src/target/<configuration>/shared, where configuration is release or

Then open the VS command prompt ( ensuring java and ant are in your PATH ) by clicking Start
> Programs > Microsoft Visual XXX ( Studio C++ whatever ) > Visual Studio Tools >
Visual Studio XXX Command Prompt ( what I called the shell, I recommend pinning this to your
start menu for easy access ). This invokes a number of batch files to correctly set up the
command line to run the complier and linker.

As an aside, I believe a lib can be a static library or a stub containing the entry points
for a dll, both are different but can wind up have the same name as it is the linker that
uses them to create the finished application.
So building a shared library will result in a dll and lib, a static lib only results in a
dll. Then again I could be wrong, I have not built a static lib on Win32 in years.

From: Jean-Denis Muys [mailto:jdmuys@mac.com]
Sent: 07 May 2010 16:48
To: Log4CXX User
Subject: Re: link error in release mode with Visual Studio 2008


Thanks for chiming in.

Unfortunately, I think I don't understand your suggestion.

Are you suggesting that I build log4cxx [Debug|Release] using ant?
Or are you suggesting that I build my client program with ant?
Or both?

In either case, why do you think ant could help with the issue I have? Why would executing
the linker from ant alleviate the "symbol not found" issues I have?

Finally, *how* would I go about doing what you suggest? How do you run ant from the VS Shell?

I'm sorry if I sound like a newbie. This is because I *am* a newbie on Windows. I am by experience
a Mac developer.



On May 7, 2010, at 17:40 , Reynolds, John wrote:

I use the ant build system from the VS shell.
In the source directory run ant for a release build or ant -Ddebug=true for a debug build

From: Jean-Denis Muys [mailto:jdmuys@mac.com]
Sent: 07 May 2010 16:11
To: Log4CXX User
Subject: Re: link error in release mode with Visual Studio 2008

yep. no change.

On May 7, 2010, at 15:57 , Fabian Jacquet wrote:

Have you tried to recompile all from clean?
Maybe the release lib is corrupted...

On Fri, May 7, 2010 at 15:47, Jean-Denis Muys <jdmuys@mac.com<mailto:jdmuys@mac.com>>
I downloaded the source code from the links at http://logging.apache.org/log4cxx/download.html
I simply compiled it following the instructions at http://logging.apache.org/log4cxx/building/vstudio.html

I had no error doing so.

I tried to track down one of those missing symbols, namely "getLogger(char const * const)".
I found the implementation LoggerPtr Logger::getLogger(const char* const name) in the file
logger.cpp. Notice the difference between the parameter signature (char const * const vs const
char* const).
It is declared in logger.h in a class that is declared:
class LOG4CXX_EXPORT Logger : ...

so it is controlled by the LOG4CXX_EXPORT macro that you described.

I am totally at loss. The source code looks fine. Everything compiles fine in both mode. The
library links fine in both mode. The client code compiles fine in both modes. The client code
links and runs fine in Debug mode, but fails to link in Release mode.

I am now trying to rebuild the log4cxx.lib library using the linker verbose mode in the hope
of seeing those symbols in the output somehow. But then, I don't know what I can do next,
whether or not they do show up.


On May 7, 2010, at 15:26 , Fabian Jacquet wrote:

<venting frustration>
Why my boss don't want I develop for MacOS X ? :-)
</venting frustration>

The class d├ęclaration must be __declspec(export) when you compile the dll and must be __declspec(import)
when you include .h from this dll. So it's correct in your error message.
It's possible that the missing symbols declarations didn't have __declspec(export) when you
compiled log4cxx.dll

Did you take sources from SVN? I compiled the source downloaded from the web site with VisualStudio
2008 without any problem.

On Fri, May 7, 2010 at 14:12, Jean-Denis Muys <jdmuys@mac.com<mailto:jdmuys@mac.com>>
When setting the linker verbose, it indeed reports that it is searching log4cxx.lib.
When setting fully verbose, it even reports *finding* symbols in log4cxx.lib with the file
that references them.
So indeed, the linker finds log4cxx.lib AND manages to find some of the symbols I use.
Also, it seems that all the found symbols have a __thiscall declaration, while all the ones
that are *not* found have a __stdcall declaration.

I have no idea whether this has any significance.

regarding the __declspec thing, I noticed that the linker says the symbols it cannot find
are __declspec(import), not __declspec(export). What are the differences between these two?
Could it be that the "export" variations are in the log4cxx.lib file but cannot be matched
to the "import" variation it's looking for?

<venting frustration>
Why is the Windows platform so poorly designed? None of those charades are necessary on the
BSD architecture that MacOS X is built upon!
</venting frustration>

I am not sure what I can do next. I'll try to look for those symbols in the log4cxx source
to check their declarations.


On May 7, 2010, at 12:02 , Fabian Jacquet wrote:

Mh, maybe those symbols are in the DLL but not in the lib. To be in the lib, it must have
__declspec(dllexport) when compiling.
log4cxx use this define to do this:
#if defined(LOG4CXX_STATIC)
//   definitions used when building DLL
#elif defined(LOG4CXX)
#define LOG4CXX_EXPORT __declspec(dllexport)
//    definitions used when using DLL
#define LOG4CXX_EXPORT __declspec(dllimport)

So, "LOG4CXX_EXPORT __declspec(dllexport)" when compiling log4cxx.dll
"LOG4CXX_EXPORT __declspec(dllimport)" when including log4cxx.h from your project.

If for some reason, LOG4CXX_STATIC is defined, it's possible that some symbols are not exported.
But I don't know how it's possible.

If you don't use more than those 13 symbols maybe nothing is exported or maybe the link don't
use log4cxx.lib.
You can check the list of lib used by the linker like this:
Project properties>Linker>General>Show Progress = /VERBOSE:LIB
The linker will dump the lib list in the output window of visual studio when compiling. Check
that you have something like that:
1>    Searching [your directories]\log4cxx.lib:

I don't know any tools to check symbols. I think you could check with notepad, you can search
about "getLogger" by example but if you find it, I don't know if you can conclude that the
symbol is right exported. If you don't find it, I think the problem comes from the lib :-)
On Fri, May 7, 2010 at 11:08, Jean-Denis Muys <jdmuys@mac.com<mailto:jdmuys@mac.com>>
Thanks for answering. I wish the solution was that simple. I apologize for not explicitly
mentioning it, but my project is - I think - set up correctly.

That is:

- both the Debug and Release configurations mention log4cxx.lib in its Linker>Input>Additional
- both the Debug and Release configurations mention a *different* directory in Linker>General>Additional
Library Directories. They are different because they point to the Debug version and the Relase
version of loc4cxx respectively (apache-log4cxx-0.10.0\projects\Debug and apache-log4cxx-0.10.0\projects\Release)

Of course both configurations of log4cxx were previously built with no failure (from its Visual
Studio project). They were built in "DLL" mode as explained on the log4cxx web site. While
doing a static library version is on my todo list, I'd rather solve the present issue first.

At this point in time, I suppose the 13 missing symbols are present in the Debug version of
the log4cxx.lib stub library, but not in the Release version. How can I verify this hypothesis?
What could explain that? How can I fix it?

Another hypothesis might be that there is yet another dependency that needs to be set in Release
mode only. This seems less plausible though. And what would it be?

Again, thanks for you answer. Any other idea on how I could make progress on this issue?



On May 7, 2010, at 10:29 , Fabian Jacquet wrote:


The project configuration is different between debug and release. In debug you certainly added
log4cxx.lib in the field "Linker/Input/Additional dependencies" but you have a drop-down which
select the configuration, if you switch to release, I think you don't have log4cxx.lib in
"Additional dependencies" .

Don't forget to add the directory of this lib in the field "Linker/General/Additional Library

log4cxx.lib is not really a static lib. It's only the interface to the dll class and functions.

I hope it help you.
On Fri, May 7, 2010 at 04:00, Jean-Denis Muys <jdmuys@mac.com<mailto:jdmuys@mac.com>>

I have a Visual Studio 2008 project using log4cxx that links (and runs) fine in Debug mode
using the Debug version of log4cxx, but fails to link in Release mode using the release version
of log4cxx. Here are the 13 undefined symbols:

1>------ Build started: Project: RepliKator04, Configuration: Release Win32 ------
1>   Creating library z:\PCdev\RepliKator2004\RK_Demo_2004\plugins\RepliKator04.bundle\contents\windows\RepliKator04.lib
and object z:\PCdev\RepliKator2004\RK_Demo_2004\plugins\RepliKator04.bundle\contents\windows\RepliKator04.exp
1>RKConnector.obj : error LNK2001: unresolved external symbol "__declspec(dllimport) public:
static class log4cxx::helpers::ObjectPtrT<class log4cxx::Level> __stdcall log4cxx::Level::getTrace(void)"
1>RepliKator04 - 13 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

As I am a Mac developer, not a Windows developer, I feel lost here. What can I do to fix that
issue? I really don't get why those symbols would not be defined in Release mode.

Note that my project is not an application, but a Plugin for a third party app.
I link against the DLL version of log4cxx. I'd rather use a static library version, but I
failed to build it so, and I could not find detailed instructions on the net to do it.

So for the time being, I am mainly interested in understanding why these link-time errors
occur, and in how to fix them.

Thanks and regards.


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