[CMake] simple project in Visual Studio 2008

[Yuri V. Timenkov]

On Tuesday 19 August 2008 17:10:56 Jos.van.den.Oever at panalytical.com wrote:
> "Yuri V. Timenkov" <ytimenkov at parallels.com> wrote on 08/19/2008 02:05:04
>
> PM:
> > Are following posts solve your problem?
> >
> > http://www.cmake.org/pipermail/cmake/2008-July/023099.html
> > http://www.cmake.org/pipermail/cmake/2006-September/011100.html
> > http://www.cmake.org/pipermail/cmake/2005-February/006080.html
>
> Yes they do. The tricky point was having to know that the symbol
> ${LIBRARYNAME}_EXPORTS is set when building the library.
> Then adding something along these lines in the header file solves the
> problem:
>
> #ifdef _WIN32
> #  ifdef testc2_EXPORTS
> #    define WHATEVER __declspec( dllexport )
> #  else
> #    define WHATEVER __declspec( dllimport )
> #  endif
> #else
> #  define WHATEVER
> #endif
>
> WHATEVER float LibC2Func();
>
> So now I can get a simple project with one dll and one exe to compile, but
> I still do not understand which program determines whether the .exe should
> link to a .lib or a .dll. Does the Microsoft Visual Studio compiler
> determine this or does CMake inspect the header files?
> I find it strange that the linking command depends on the contents of the
> header files. Is there a reason for this?
This is VS tricks. Studio generates 2 files: one import library (.lib) and one 
- dynamic library (.dll). gcc (and mingw family) exports all symbols by 
default, VS doesn't export anything by default. And if your dll doesn't  
export anything, VS simply doesn't generate import library (for example, if 
you generate resource-only dll). The only thing cmake knows is when you using 
VS generator, library extension to link with -- is .lib. And when you use 
__declspec( dllexport ), cl.exe puts special marks in objects indicating that 
this symbol should be exported or imported. Also, VS can tell linker to add 
some library, as it boost does with #pragma's.

Really, this is well-known issue for VS developers ("Where is my .lib file??? 
>:-("), especially if you copy project and header files and forgot change 
defines. But because CMake makes migration to windows very smooth, this 
question appears near every month in this list as cmake on VS/Windows newbie 
question.

>
> Cheers,
> Jos
>
>
>
> Jos van den Oever - SW Engineering
>
> PANalytical
> Lelyweg 1
> 7602 EA Almelo
> The Netherlands
> T   +31 (0)546 528
> F   +31 (0)546 534598
> Jos.van.den.Oever at panalytical.com
> www.PANalytical.com
>
>
>  PANalytical
> The Analytical X-ray Company
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