Class declaration

[Fab]

Dear All

I am trying to understand a part of code in a Paraview plugin from an
OpenFOAM code, an open source CFD code. There is a part of a class
declaration in a header file I don't understand, here's the specific
code of it

/*---------------------------------------------------------------------------*\
Class vtkPV3blockMeshReader Declaration
\*---------------------------------------------------------------------------*/

class VTK_IO_EXPORT vtkPV3blockMeshReader
:
public vtkMultiBlockDataSetAlgorithm
{
public:
vtkTypeMacro(vtkPV3blockMeshReader, vtkMultiBlockDataSetAlgorithm);
void PrintSelf(ostream&, vtkIndent);

(code continues here)


The declared class is vtkPV3blockMeshReader, why or what is the
VTK_IO_EXPORT preceding the class name? I could not find any example of
this kind elsewhere. Can someone elaborate on this for me?

Thanks + regards
Fab

 

[Jorgen Grahn]

Dear All

I am trying to understand a part of code in a Paraview plugin from an
OpenFOAM code, an open source CFD code. There is a part of a class
declaration in a header file I don't understand, here's the specific
code of it
....
class VTK_IO_EXPORT vtkPV3blockMeshReader ....

The declared class is vtkPV3blockMeshReader, why or what is the
VTK_IO_EXPORT preceding the class name? I could not find any example of
this kind elsewhere. Can someone elaborate on this for me?

Like the name suggests, it's something specific to that library you're
using, and probably to the compiler you use too. It's not standard
C++; it's a macro which expands into something, for some reason.

Google seems to give 16,400 hits for VTK_IO_EXPORT ... have you tried
that?

/Jorgen

 

[Öö Tiib]

class VTK_IO_EXPORT vtkPV3blockMeshReader
:
public vtkMultiBlockDataSetAlgorithm
{
(code continues here)


The declared class is vtkPV3blockMeshReader, why or what is the
VTK_IO_EXPORT preceding the class name? I could not find any example of
this kind elsewhere. Can someone elaborate on this for me?

This is likely a macro (defined elsewhere in the code of that library) to
achieve that dynamic linkage extensions to the language (that are present
in several implementations) work.

Standard C++ does not have modules, so it does not have dynamically
loadable modules and so does not have symbols (classes, variables,
functions) with dynamic linkage.