[CMake] Win32: DLL fails to find Qt symbols but .so builds in Linux

[Mike Jackson]

is COMMS_EXP being defined somewhere for WIN32?

You usually have a block of code like the following:

#if defined (_WIN32) && defined (BUILD_SHARED_LIBS)
#pragma warning(disable: 4251)
   #if defined(Comms_EXPORTS)
     #define  COMMS_EXP __declspec(dllexport)
   #else
     #define  COMMS_EXP __declspec(dllimport)
   #endif /* Comms_EXPORTS */
#else /* defined (_WIN32) && defined (BUILD_SHARED_LIBS)  */
  #define COMMS_EXP
#endif


--  
Mike Jackson   Senior Research Engineer
Innovative Management & Technology Services


On Nov 23, 2007, at 7:21 AM, Stephen Collyer wrote:

> I'm building some simple shared libraries and an executable
> that links against them under both Win32 and Linux. All of
> the libraries and exe build and link correctly under Linux,
> but when building the DLLs under Win32 I get link errors.
>
> e.g. I have a class that looks like this:
>
> #include <QMutex>
> #include <QQueue>
> #include <QString>
> #include <QWaitCondition>
>
> ...
>
> class COMMS_EXP Comms
> {
>     public:
>     ...
>
>     private:
>         QQueue<QString> messageq;
>         QMutex          qmutex;
>         QWaitCondition  message_available;
> };
>
> with a cmake command like this:
>
> ADD_LIBRARY(Comms Comms.cpp)
>
> When I build the appropriate project in VS, I get LNK2019 messages
> relating to QMutex, QWaitCondition, and so on (I've attached a small
> section of these).
>
> I'm not at all clear what's going on here, and I don't even
> understand why VS has a "link" stage when building a DLL.
> Can anyone explain ? The only possibility I can think of is
> that the linker is looking for the export lists from the
> Qt libraries (i.e. the .lib files) but is failing to find them.
>
> --  
> Regards
>
> Steve Collyer
> Netspinner Ltd
> ------ Build started: Project: Comms, Configuration: Debug Win32  
> ------
> Compiling...
> Comms.cpp
> Compiling manifest to resources...
> Linking...
>    Creating library Debug\Comms.lib and object Debug\Comms.exp
> Comms.obj : error LNK2019: unresolved external symbol "__declspec 
> (dllimport) public: __thiscall QMutex::~QMutex(void)" (__imp_?? 
> 1QMutex@@QAE at XZ) referenced in function __unwindfunclet$?? 
> 0Comms@@QAE at XZ$0
> Comms.obj : error LNK2019: unresolved external symbol "__declspec 
> (dllimport) public: __thiscall QWaitCondition::QWaitCondition 
> (void)" (__imp_??0QWaitCondition@@QAE at XZ) referenced in function  
> "public: __thiscall Comms::Comms(void)" (??0Comms@@QAE at XZ)
> C
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