Mark types used in template instantiatious explicitly as visible

base/export_template_type.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.

[Mark Mentovai, 2013/02/28 15:39:22]

2013

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_EXPORT_TEMPLATE_TYPE_H_
+#define EXPORT_TEMPLATE_TYPE_H_

[Mark Mentovai, 2013/02/28 15:39:22]

This is not the same name that you check for on the line above.

+
+// Class forward declarations usually don't need to be decorated with EXPORT.
+// However, clang looks at the visibility of forward declarations for explicit
+// template instantiations and hides the instantiated symbols if any of the
+// types isn't visible, so class declarations used in explicit macro
+// instantiations do need EXPORT.
+// But gcc warns "type attributes ignored after type is already defined" if
+// it sees an EXPORT on a class declaration after seeing the class itself (which
+// can happen depending on include order), so define a macro for this purpose.
+// To be used like:
+//
+// EXPORT_TEMPLATE_TYPE(class, UI_EXPORT, Insets);
+// extern template class MyTemplate<Insets>;
+
+#if defined(__clang__)
+#define EXPORT_TEMPLATE_TYPE(kw, export_macro, name) kw export_macro name
+#else
+#define EXPORT_TEMPLATE_TYPE(kw, export_macro, name) kw name
+#endif
+
+#endif  // EXPORT_TEMPLATE_TYPE_H_