Add missing visibility compiler flags

We have been building the shared library for Epoxy without the symbol
visibility flags for the compiler, which means we've been leaking
internal symbols all over the floor.

Fixes: #111

meson.build

@@ -140,9 +140,11 @@ foreach cflag: test_cflags
   endif
 endforeach
 
-# Visibility compiler flags
+libtype = get_option('default_library')
-visibility_cflags = []
+
-if get_option('default_library') != 'static'
+# Visibility compiler flags; we only use this for shared libraries
+if libtype == 'shared'
+  visibility_cflags = []
   if host_system == 'windows'
     conf.set('DLL_EXPORT', true)
     if cc.get_id() == 'msvc'
@@ -152,7 +154,7 @@ if get_option('default_library') != 'static'
       visibility_cflags += [ '-fvisibility=hidden' ]
     endif
   else
-    conf.set('EPOXY_PUBLIC', '__attribute__((visibility("default")))')
+    conf.set('EPOXY_PUBLIC', '__attribute__((visibility("default"))) extern')
     visibility_cflags += [ '-fvisibility=hidden' ]
   endif
 endif

src/meson.build

@@ -68,8 +68,6 @@ if host_system == 'windows'
 endif
 
 # Allow building a static version of epoxy
-libtype = get_option('default_library')
-
 if libtype != 'shared'
   libepoxy_static = static_library('epoxy',
                                    sources: epoxy_sources + epoxy_headers,
@@ -88,7 +86,7 @@ if libtype != 'static'
                                    install: true,
                                    dependencies: epoxy_deps,
                                    include_directories: libepoxy_inc,
-                                   c_args: common_cflags,
+                                   c_args: common_cflags + visibility_cflags,
                                    link_args: common_ldflags)
   libepoxy = libepoxy_shared
 endif