> > #if BUILDING_LIBFOO && HAVE_VISIBILITY
> > #define LIBFOO_DLL_EXPORTED
__attribute__((__visibility__("default")))
> > #elif BUILDING_LIBFOO && defined _MSC_VER
> > #define LIBFOO_DLL_EXPORTED __declspec(dllexport)
> > #elif defined _MSC_VER
> > #define LIBFOO_DLL_EXPORTED __declspec(dllimport)
> > #else
> > #define LIBFOO_DLL_EXPORTED
> > #endif
> >
> > Trouble is, this doesn't handle the case where I'm
> > building a static lib using MS tools. In that case I
> > (think I) want the macro to be empty.
>
> libtool should be adding -DPIC only for the non-static
> objects, that should allow you to distinguish between that
> and the objects that are used for the DLL.
Having LIBFOO_DLL_EXPORTED depend on whether PIC is defined works for
building libfoo itself -- the shared library have exports decorated with
__declspec(dllexport) and for the static library, LIBFOO_DLL_EXPORTED is
empty. My macros look like this now:
#if BUILDING_LIBFOO && HAVE_VISIBILITY
# define LIBFOO_DLL_EXPORTED __attribute__((__visibility__("default")))
#elif defined _MSC_VER
# if BUILDING_LIBFOO && defined(PIC)
# define LIBFOO_DLL_EXPORTED __declspec(dllexport)
# elif !defined(BUILDING_LIBFOO)
# define LIBFOO_DLL_EXPORTED __declspec(dllimport)
# else
# define LIBFOO_DLL_EXPORTED
# endif
#else
# define LIBFOO_DLL_EXPORTED
#endif
For the _MSC_VER case, I read the three alternatives like this:
1. If building a shared version of libfoo: __declspec(dllexport)
2. else if using libfoo (shared or static): __declspec(dllimport)
3. else (i.e. building a static version of utils): nothing
but it turns out this is insufficient. #1 and #3 are correct, but to make
LIBFOO_DLL_EXPORTED correct all the time I need to split #2 into separate
cases. __declspec(dllimport) is correct when using a shared libfoo, but
when using a static libfoo, I need LIBFOO_DLL_EXPORTED to be empty. I'm
loving M$ at the moment.
One way to resolve this is to provide some extra (aka project-specific)
option at configure time so users can specify that they want static or
shared. Then I can use that in my preprocessor logic and pass -all-static
or -static or -static-libtool-libs (haven't figured out which yet) in
blah_LDFLAGS.
Working on this now. Curious what people think of this, and if there's a
better way that I'm missing (other than ditching MS which unfortunately
isn't an option at the moment).
Thanks.
-DB
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