c++ - Macro before class name -

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i looking on code , i've stumble upon this:

class idata_export idata {     /* .... */ }

where idata_export not more :

#ifndef idata_export     #define idata_export #endif

what idata_export in case? (i mean, type int, char etc ... ?)

most @ point in time, or under conditions defined (for example, under msvc):

#define idata_export __declspec(dllexport)

which used indicate classes publicly export library.

using macro, developer alternate between exporting classes , not exporting anything, without having go on each individual class.

this part of macro pattern alternates between importing , exporting classes, depending on whether code compiled library, or program dependent on library. like:

#ifdef is_library // <--this defined when compiling library!    #define idata_export __declspec(dllexport)   #else    #define idata_export __declspec(dllimport)   #endif

for more information, see dllexport, dllimport on msdn


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