Re: member function level dll export
On Thu, 24 Apr 2008 17:59:22 -0700 (PDT), qdin <eryqdin@gmail.com> wrote:
Thanks for your explanation. It's all very clear now.
I do have one more question, now about static function dll exporting.
Basically - if I use __declspec(dllexport), does it export by name or
by ordinal?
Always by name.
I have a class with only static functions in it (the Factory class I
mentioned above).
I export each of these functions with __declspec(dllexport).
It's easier to dllexport the whole class, even a factory class like yours.
I would either dllexport the whole thing or use a namespace instead of a
class.
I trust you're using the macro technique to accomplish this, e.g.
#ifdef COMPILING_X_DLL
#define X_EXPORT __declspec(dllexport)
#else
#define X_EXPORT __declspec(dllimport)
#endif
You would replace "X" with the name of your DLL or something sufficiently
unique. The dllimport side is important to help the compiler generate more
efficient function calls.
So I compiled this into a dll, and a link .lib,
then compiled the link .lib into my client app.
After this, I added (and exported) another static function in front of
all other functions in the class, and compiled again.
I did NOT relink the .lib into my client application.
When I swap the new dll in, everything still works, and the proper
functions are being called.
I checked both dlls in depends.exe, and have seen that the ordinals on
some functions do change between the two dlls,
yet these functions work regardless of the dll that I use.
I guess this would imply that it exports by name in this case (?)...
Yep.
but then that raises the question of why you would want to export by
ordinal in the first place?
Ordinals takes up less space, are faster to bind when the DLL is loaded,
and provide a tiny bit of obscurity. None of these reasons are very
compelling.
--
Doug Harrison
Visual C++ MVP