Make embind work with -fvisibility=hidden

system/include/emscripten/val.h

@@ -285,7 +285,7 @@ struct WireTypePack {
 static const char name##_symbol[] = #name;                          \
 static const ::emscripten::internal::symbol_registrar<name##_symbol> name##_registrar
 
-class val {
+class EMBIND_VISIBILITY_DEFAULT val {
 public:
   // missing operators:
   // * ~ - + ++ --

system/include/emscripten/wire.h

@@ -24,6 +24,7 @@
 #include <string>
 
 #define EMSCRIPTEN_ALWAYS_INLINE __attribute__((always_inline))
+#define EMBIND_VISIBILITY_DEFAULT __attribute__((visibility("default")))
 
 #ifndef EMSCRIPTEN_HAS_UNBOUND_TYPE_NAMES
 #define EMSCRIPTEN_HAS_UNBOUND_TYPE_NAMES 1
@@ -430,7 +431,7 @@ constexpr bool typeSupportsMemoryView() {
 } // namespace internal
 
 template<typename ElementType>
-struct memory_view {
+struct EMBIND_VISIBILITY_DEFAULT memory_view {
     memory_view() = delete;
     explicit memory_view(size_t size, const ElementType* data)
         : size(size)

test/test_core.py

@@ -7718,6 +7718,36 @@ def test_source_map(self, args):
     else:
       self.assertTrue(seen_lines.issuperset([6, 7, 11, 12]), seen_lines)
 
+  @needs_dylink
+  def test_embind_dylink_visibility_hidden(self):
+    # Check that embind is usable from a library built with "-fvisibility=hidden"
+
+    create_file('liblib.cpp', r'''
+      #include <emscripten/val.h>
+      #define EXPORT __attribute__((visibility("default")))
+      using namespace emscripten;
+      EXPORT void liba_fun() {
+        unsigned char buffer[1];
+        val view(typed_memory_view(1, buffer));
+      }
+    ''')
+    self.build_dlfcn_lib('liblib.cpp', emcc_args=['-fvisibility=hidden'])
+
+    self.prep_dlfcn_main()
+    self.clear_setting('NO_AUTOLOAD_DYLIBS')
+    create_file('main.cpp', r'''
+      #include <stdio.h>
+      #include <emscripten/val.h>
+      using namespace emscripten;
+      void liba_fun();
+      int main() {
+        liba_fun();
+        printf("done\n");
+        return 0;
+      }
+    ''')
+    self.do_runf('main.cpp', 'done\n', emcc_args=['--bind'])
+
   @no_wasm2js('TODO: source maps in wasm2js')
   def test_dwarf(self):
     self.emcc_args.append('-g')