dbus: Make it possible to build as shared_library.

dbus/dbus_export.h

+// Copyright 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef DBUS_DBUS_EXPORT_H_
+#define DBUS_DBUS_EXPORT_H_
+
+// Defines CHROME_DBUS_EXPORT so that functionality implemented by the dbus
+// library can be exported to consumers.
+// NOTE: We haven't used DBUS_EXPORT because it would conflict with the version
+// from /usr/include/dbus-1.0/dbus/dbus-macros.h.
+
+#if defined(COMPONENT_BUILD)
+#if defined(WIN32)
+
+#if defined(DBUS_IMPLEMENTATION)

[satorux1, 2012/11/02 01:21:56]

Why do we need to check this? What happens if we don't have it here?

[tfarina, 2012/11/02 01:31:05]

within src/dbus/ library we do DBUS_IMPLEMENTATION=1, that means we are
'exporting' our APIs to consumers, that is __declspec(dllexport) for Windows.

When clients are using src/dbus/ library, they have DBUS_IMPLEMENTATION=0,
because they are importing our APIs.

That is the way I see it, and I'm pretty sure without it doesn't work.

I just removed the define from the gyp file and recompiled dbus_unittests, we
get a ton of errors like the one below:

FAILED: flock linker.lock clang++ -B/usr/local/gold/bin -pthread
-Wl,-z,noexecstack -fPIC -Wl,--threads -Wl,--thread-count=4
-B../../third_party/gold -L/usr/lib/x86_64-linux-gnu -Wl,--icf=none -o
dbus_unittests -Wl,-rpath=\$ORIGIN/lib -Wl,--start-group
obj/dbus/dbus_unittests.bus_unittest.o
obj/dbus/dbus_unittests.end_to_end_async_unittest.o
obj/dbus/dbus_unittests.end_to_end_sync_unittest.o
obj/dbus/dbus_unittests.message_unittest.o
obj/dbus/dbus_unittests.mock_unittest.o
obj/dbus/dbus_unittests.property_unittest.o
obj/dbus/dbus_unittests.signal_sender_verification_unittest.o
obj/dbus/dbus_unittests.string_util_unittest.o
obj/dbus/dbus_unittests.test_service.o
obj/dbus/dbus_unittests.values_util_unittest.o obj/dbus/libdbus_test_proto.a
obj/testing/libgtest.a obj/base/libbase_static.a obj/base/libtest_support_base.a
obj/third_party/protobuf/libprotobuf_lite.a obj/base/librun_all_unittests.a
obj/dbus/libdbus_test_support.a obj/testing/libgmock.a lib/libbase_i18n.so
lib/libbase.so lib/libdbus.so -Wl,--end-group -lrt -ldl -lgtk-x11-2.0
-lgdk-x11-2.0 -latk-1.0 -lgio-2.0 -lpangoft2-1.0 -lpangocairo-1.0
-lgdk_pixbuf-2.0 -lm -lcairo -lpango-1.0 -lfreetype -lfontconfig -lgobject-2.0
-lgmodule-2.0 -lgthread-2.0 -lglib-2.0 -ldbus-1 -lpthread
/usr/local/gold/bin/ld: obj/dbus/dbus_unittests.end_to_end_sync_unittest.o: in
function
EndToEndSyncTest_Echo_Test::TestBody():../../dbus/end_to_end_sync_unittest.cc:57:
error: undefined reference to 'dbus::MethodCall::MethodCall(std::string const&,
std::string const&)'

[satorux1, 2012/11/02 01:43:58]

Thanks. I found the same thing in sql/sql.gyp,

      'defines': [ 'SQL_IMPLEMENTATION' ],

so I'm assuming this is the standard way to make libraries ready for component
build

+#define CHROME_DBUS_EXPORT __declspec(dllexport)
+#else
+#define CHROME_DBUS_EXPORT __declspec(dllimport)
+#endif  // defined(DBUS_IMPLEMENTATION)
+
+#else  // !defined(WIN32)
+
+#if defined(DBUS_IMPLEMENTATION)
+#define CHROME_DBUS_EXPORT __attribute__((visibility("default")))
+#else
+#define CHROME_DBUS_EXPORT
+#endif
+
+#endif  // defined(WIN32)
+
+#else  // !defined(COMPONENT_BUILD)
+
+#define CHROME_DBUS_EXPORT
+
+#endif  // defined(COMPONENT_BUILD)
+
+#endif  // DBUS_DBUS_EXPORT_H_