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From Jean-Denis Muys <jdm...@mac.com>
Subject Re: link error in release mode with Visual Studio 2008
Date Fri, 07 May 2010 13:47:01 GMT
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> wrote:
> 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.
> Jean-Denis
> 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)
>> #define LOG4CXX_EXPORT
>> //   definitions used when building DLL
>> #elif defined(LOG4CXX)
>> #define LOG4CXX_EXPORT __declspec(dllexport)
>> #else
>> //    definitions used when using DLL
>> #define LOG4CXX_EXPORT __declspec(dllimport)
>> #endif
>> So, "LOG4CXX_EXPORT __declspec(dllexport)" when compiling log4cxx.dll
>> and
>> "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> wrote:
>> 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
>> Regards,
>> Jean-Denis
>> On May 7, 2010, at 10:29 , Fabian Jacquet wrote:
>>> Hi,
>>> 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 Directories"
>>> 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> wrote:
>>> Hi,
>>> 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>Linking...
>>> 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
>>> 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.
>>> Jean-Denis

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