Writing portable libraries

[aaronfude]

Hi,

Perhaps this is slightly offtopic.

Coming into the Windows world from Unix.

Is there a reference on writing C++ libraries in a portable way.

For example, right now I'm sticking "__declspec(dllexport)" in front of
each of my classes. I guess I can still make it work on Unix bydefing
__declspec(x) to be an empty macro, but that's embarrassing.

Is there a better solution?

Many thanks in advance!

Aaron

[Torsten Mueller]

aa*******@gmail.com schrieb:

For example, right now I'm sticking "__declspec(dllexport)" in front
of each of my classes. I guess I can still make it work on Unix
bydefing __declspec(x) to be an empty macro, but that's
embarrassing.

Is there a better solution?

Normally this __declspec() stuff is already in a global #define
because in most cases you use the same header for compiling the
library (this needs __declspec(dllexport)) and for using the library
(this needs __declspec(dllimport)). So the class definitions normally
contain something like this:

#ifdef BUILD_LIB
#define LIB_CLASS __declspec(dllexport)
#else
#define LIB_CLASS __declspec(dllimport)
#endif

class LIB_CLASS MyClass {
// ...
};

If you now want to have portable libraries you must just extend the
LIB_CLASS macro. For most Unix compilers you would leave it blank.
Note: you need to define this macro just on one single place in the
entire project, so it's not really much effort.

T.M.

[benben]

Another way of writing portable code is not to export classes. Try to use
pure abstract classes and global functions.

ben

"Torsten Mueller" <de******@shared-files.de> wrote in message
news:u4***********@fastmail.fm...

aa*******@gmail.com schrieb:

For example, right now I'm sticking "__declspec(dllexport)" in front
of each of my classes. I guess I can still make it work on Unix
bydefing __declspec(x) to be an empty macro, but that's
embarrassing.

Is there a better solution?

Normally this __declspec() stuff is already in a global #define
because in most cases you use the same header for compiling the
library (this needs __declspec(dllexport)) and for using the library
(this needs __declspec(dllimport)). So the class definitions normally
contain something like this:

#ifdef BUILD_LIB
#define LIB_CLASS __declspec(dllexport)
#else
#define LIB_CLASS __declspec(dllimport)
#endif

class LIB_CLASS MyClass {
// ...
};

If you now want to have portable libraries you must just extend the
LIB_CLASS macro. For most Unix compilers you would leave it blank.
Note: you need to define this macro just on one single place in the
entire project, so it's not really much effort.

T.M.

[Torsten Mueller]

"benben" <be******@hotmail.com> schrieb:

Another way of writing portable code is not to export classes. Try
to use pure abstract classes and global functions.

Ah, you mean native classes in the module using the library, calling
exported library functions. This is exactly what import libraries do.

Nevertheless also exported functions require __declspec(dllexport) in
MSVC, otherwise nothing is exported. AFAIR the __declspec(dllimport)
is redundant on functions.

T.M.

[aaronfude]

Really, there isn't a way to export stuff with a .def file?

I'm really trying to avoid "__declspec(dllexport)" (b/c it is so ugly).