On 9/23/2010 6:25 PM, Peter Rosin wrote:
> I don't know how to set up the defines so that EXTERN becomes
>
> 1. "extern" when you use a static library
> 2. "extern" when you build a static library
> 3. "extern declspec(dllimport)" when you use a shared library
> 4. "extern declspec(dllexport)" when you build a shared library
>
> I could fix 2 and 4, but separating 1 and 3 is not possible. Since
> extern declspec(dllimport) works everywhere with MSVC I'm taking the
> easy option with this patch.
>
> Or should I add -DBUILDING_FOO to Makefile.am and variations of the below
> to the code?
That is the typical approach. The drawback -- usually an acceptable one
-- is that if you are building a "stack" of dependent DLLs:
EXE --> C.DLL -> B.DLL
--> A.DLL
Then (a) you must link exe using .obj's compiled as pic (e.g. with
-DDLL_EXPORT, even tho the EXE *itself* is not a "shared library").
libtool does this by default IIRC. (b) You MUST link EXE against shared
C.DLL and shared A.DLL; you can't link against static C.lib and B.lib,
but dynamic A.DLL, or vice versa (because DLL_EXPORT, for EXE's objs,
either IS, or IS NOT, defined).
We already enforce the restriction that C.DLL can't depend on B.lib, so
that "complication" is a non-issue.
> #ifdef _MSC_VER
> # ifdef BUILDING_FOO
> # ifdef DLL_EXPORT
> # define EXTERN extern declspec(dllexport)
> # endif
> # else
> # define EXTERN extern declspec(dllimport)
> # endif
> #endif
> #ifndef EXTERN
> # define EXTERN extern
> #endif
More indepth review against your revised version.
--
Chuck
