MinGW: Use __declspec(dllexport) or __attribute__((visibility("default")))?

Question

Does MinGW support __declspec(dllexport)/__declspec(dllimport)? Even if it does, should I rather use __attribute__((visibility("default")))? Basically should I decide what to use based on the platform or the compiler?

Should it be like this?

#ifdef _MSC_VER
#   ifdef MYLIB_EXPORTS
#       define MYLIB_API __declspec(dllexport)
#   else
#       define MYLIB_API __declspec(dllimport)
#   endif
#else
#   define MYLIB_API __attribute__((visibility("default")))
#endif

Or like this?

#if defined(_WIN32) || defined(_WIN64)
#   ifdef MYLIB_EXPORTS
#       define MYLIB_API __declspec(dllexport)
#   else
#       define MYLIB_API __declspec(dllimport)
#   endif
#else
#   define MYLIB_API __attribute__((visibility("default")))
#endif

And what about things like __declspec(align(16)) Vs. __attribute__((aligned(16)))?

Answer 1

Visibility Vs. dllexport is a platform thing, not a compiler thing. So using __declspec(dllexport)/__declspec(dllimport) (or __attribute__((dllexport))/__attribute__((dllimport))) with MinGW is the way to go. See: http://gcc.gnu.org/wiki/Visibility#How_to_use_the_new_C.2B-.2B-_visibility_support

Answer 2

Yes MinGW supports __declspec dllimport/dllexport (http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html). You should use it, if it makes easier to support multiple compilers. In general compiler specific attributes are not portable, and you should use macro wrappers (as in your example).