use of dllexport in win32

[Gary Bartlett]

I noticed that the win32 version of config.h defines __EXPORT as __declspec(dllexport).  This is great for compiling the Common C++ library, but when trying to use/import the library in our own programs it causes the entire library to be re-exported from our programs too.  The usual way of handling this seems to be with something like

#ifdef CXX_EXPORTS
#define    __EXPORT    __declspec(dllexport)
#else
#define    __EXPORT    __declspec(dllimport)
#endif

and then CXX_EXPORTS is added to the project to build the library and omitted from projects that just import it.

I'm new to Common C++ and SourceForge, so any guidance on how things like this should be reported would be appreciated.

Thanks,
Gary

[David Sugar]

Hmm...let me think about this one...__EXPORT then isn't really a good name for this, since it can also be an "import", by default...

[Kevin Walsh]

A typical msdev template would say something along the following:

#define __EXPORT __declspec(dllexport)
#define __IMPORT __declspec(dllimport)
// on unix, just declare empty __EXPORT and __IMPORT macros

// then do
#ifdef CCXX_EXPORTS // define in makefile or project
#define CCXX_API __EXPORT
#else
#define CCXX_API __IMPORT
#endif

#ifdef CCIO_EXPORTS
#define CCIO_API __EXPORT
#else
#define CCIO_API __IMPORT
#endif
// etc.

This also makes it easy to figure out which classes belong in each of the 3 dlls.  On win32, you really want to __IMPORT the ccxx and ccio classes when __EXPORTing the ccstd classes, and so on.  This is pretty clear if you use CCXX_API or CCIO_API or whatnot.

-kevin

[Frediano Ziglio]

Mm... there are no need to use code such

#ifdef CCXX_EXPORTS // define in makefile or project
#define CCXX_API __EXPORT
#else
#define CCXX_API __IMPORT
#endif

config.h for default declare __EXPORT as __declspec(import). This is overwritten in export.h (included in all implementation, not headers).

I have changed export declaration with 4 macro:
CCXX_EXPORT()
CCXX_MEMBER()
CCXX_MEMBER_EXPORT()
CCXX_CLASS_EXPORT
(i will extend use for specify different linkage explicitly)