-fvisibility=hidden

setup.py

@@ -53,6 +53,8 @@ class BuildExt(build_ext):
         opts = self.c_opts.get(ct, [])
         if ct == 'unix':
             opts.append(cpp_flag(self.compiler))
+            if has_flag(self.compiler, '-fvisibility=hidden'):
+                opts.append('-fvisibility=hidden')
         for ext in self.extensions:
             ext.extra_compile_args = opts
         build_ext.build_extensions(self)