Properly set up visibility for static builds.

Should finally fix the dreaded Clang linker warning on macOS.

Author: mosra

doc/corrade-changelog.dox

@@ -142,6 +142,12 @@ namespace Corrade {
     for more information when using custom buildsystems, see also
     [mosra/corrade#51](https://github.com/mosra/corrade/issues/51).
 -   Fixed compilation with Clang and `-std=gnu++14` (see [mosra/corrade#62](https://github.com/mosra/corrade/pull/62)
+-   @ref CORRADE_VISIBILITY_STATIC no longer exports symbols in static
+    libraries to be consistent with hidden visibility by default, additionally
+    `-fvisibility-inlines-hidden` is passed along with `-fvisibility=hidden`
+    when @ref corrade-cmake "CORRADE_USE_PEDANTIC_FLAGS" property is enabled in
+    CMake on GCC and Clang to avoid linker warnings on macOS (see
+    [mosra/corrade#53](https://github.com/mosra/corrade/issues/53))
 
 @subsection corrade-changelog-latest-bugfixes Bug fixes
 

modules/UseCorrade.cmake

@@ -73,7 +73,13 @@ if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR (CMAKE_CXX_COMPILER_ID MATCHES "(Appl
         "-Werror=return-type"
         "-Wmissing-declarations"
         "-pedantic"
-        "-fvisibility=hidden")
+        # Needs to have both, otherwise Clang's linker on macOS complains that
+        # "direct access in function [...] to global weak symbol [...] means the
+        # weak symbol cannot be overridden at runtime. This was likely caused
+        # by different translation units being compiled with different
+        # visibility settings." See also various google results for the above
+        # message.
+        "-fvisibility=hidden" "-fvisibility-inlines-hidden")
 
     # Some flags are not yet supported everywhere
     # TODO: do this with check_c_compiler_flags()

src/Corrade/Utility/VisibilityMacros.h

@@ -50,13 +50,12 @@
 #endif
 
 /** @hideinitializer
- * @brief Public symbol in a static library
- */
-#ifdef CORRADE_TARGET_WINDOWS
+@brief Public symbol in a static library
+
+Defined as empty --- to be consistent with hidden visibility by default,
+symbols in static libraries shouldn't be exported either.
+*/
 #define CORRADE_VISIBILITY_STATIC
-#else
-#define CORRADE_VISIBILITY_STATIC __attribute__ ((visibility ("default")))
-#endif
 
 /** @hideinitializer
 @brief Local symbol