[Insight-developers] ITK_EXPORT and the Dark side of the Force...

[Bill Hoffman]

Hi,

I have a few questions/statements about this problem:

1. itkWin32Header is included by itkMacro.h, so it should be included everywhere.
If it was not included with each file that used ITK_EXPORT, you would get a
syntax error??


2. For the static builds, we should add ITKSTATIC.  It is possible to
build other than shared.

3. I think the warning is disabled because of some stl issues.  So,
for the Dashboard we have to leave it disabled.


At 01:00 PM 5/2/2001 -0400, Luis Ibanez wrote:

>Hi
>
>After several days of debugging and existentialist crisis
>the following problem have been cleared.
>
>In our beloved file  Code/Common/itkWin32Header.h  we have
>the following declaration for the symbol ITK_EXPORT:
>
>
>
>#if defined(_WIN32) || defined(WIN32)
># ifndef ITKSTATIC
>#  ifdef  ITKDLL
>#   define ITK_EXPORT  __declspec( dllexport )
>#  else
>#   define ITK_EXPORT  __declspec( dllexport )
>#  endif
># else
>#  define ITK_EXPORT
># endif // ITKSTATIC
>#else
>// Now for the UNIX stuff
>#define ITK_EXPORT
>
>#endif
>
>
>
>Currently the symbols ITKSTATIC and ITKDLL are not
>being defined. So ITK_EXPORT is being defined as
>__declspec( dllexport ).  Unfortunately it seems
>that a number of files containing the ITK_EXPORT
>don't have itkWin32Header among their visible
>includes.  The consequence is that in some parts
>the symbol ITK_EXPORT is going just in blank.
>
>The conflict with this situation arises when a
>base class A do have ITK_EXPORT == __declspec(dllexport)
>and some other class B deriving from A, have ITK_EXPORT
>in blank.  Virtual functions declared in A have a
>particular calling sequence, while the corresponding
>functions on B use a different one.
>
>The warning that protests about this situation is
>now being disabled in the same file itkWin32Header.
>(Warning 4251).  The confict only appear at running
>time when a virtual function (in the A->B case) is
>called, the stack end up in an inconsistent state,
>and an exception is thrown.
>
>
>
>--
>
>
>Here are some options to get around this problem:
>
>
>1) Define ITKSTATIC in a CMakeList.txt file,
>   given that we are now only creating static
>   libraries.
>
>
>2) Remove the __declspec(dllexport) in the else
>   part of the ifdef ITKDLL, so when ITKDLL is NOT
>   defined (our current case), ITK_EXPORT will be
>   blank everywhere.
>
>
>3) Figure out a way to ensure that all the files
>   that contain a ITK_EXPORT include directly or
>   indirectly itkWin32Header.h
>   It is not the case right now.
>
>
>4) Remove the line disabling the warning 4251.
>
>
>
>---
>
>(1) and (2) should go together
>(4) should in principle help with (3).
>
>
>
>
>I would suggest to do (1) and (2) first,
>which are quite easy, and maybe later do
>(3) and (4), to cover all the combinations.
>
>
>
>
>Any ideas ?
>
>
>
>
>
>
>
>Luis
>
>
>
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