Componentize protobuf_lite

third_party/protobuf/src/google/protobuf/stubs/common.h

Index: third_party/protobuf/src/google/protobuf/stubs/common.h
diff --git a/third_party/protobuf/src/google/protobuf/stubs/common.h b/third_party/protobuf/src/google/protobuf/stubs/common.h
index 00af41a35ece90ad24aa429ef5e46a31c202595d..cad22fa6c3bfe59fd90ad3a9845d65a7bfc21309 100644
--- a/third_party/protobuf/src/google/protobuf/stubs/common.h
+++ b/third_party/protobuf/src/google/protobuf/stubs/common.h
@@ -85,18 +85,33 @@ namespace protobuf {
   TypeName(const TypeName&);                           \
   void operator=(const TypeName&)
 
-#if defined(_MSC_VER) && defined(PROTOBUF_USE_DLLS)
-  #ifdef LIBPROTOBUF_EXPORTS
-    #define LIBPROTOBUF_EXPORT __declspec(dllexport)
-  #else
-    #define LIBPROTOBUF_EXPORT __declspec(dllimport)
+// The macros defined below are required in order to make protobuf_lite a
+// component on all platforms. See http://crbug.com/172800.
+#if defined(COMPONENT_BUILD) && defined(PROTOBUF_USE_DLLS)

[Dirk Pranke, 2013/01/31 02:15:06]

are there cases where COMPONENT_BUILD != PROTOBUF_USE_DLLS? Can we just use the
latter and define PROTOBUF_USE_DLLs conditionally in the gyp file? or is
USE_DLLs windows-specific?

[Raghu Simha, 2013/01/31 03:14:40]

Unfortunately, we must condition these exports on PROTOBUF_USE_DLLS and
COMPONENT_BUILD because protobuf_lite.gypi is consumed in two places -- by the
component protobuf_lite and by the static library protobuf_full_do_not_use.

- We must condition the exports on COMPONENT_BUILD for the obvious reason that
we don't want the export defs to be active when chrome is being built in static
mode.
- We must also condition them on PROTOBUF_USE_DLLS, because, while we want the
exports to be active in protobuf_lite for component builds, we do not want them
to be active in protobuf_full_do_not_use, even if component builds are enabled.
Otherwise, we end up with inconsistent dll linkage warnings while trying to
build protoc.

Obviously, it would be much simpler if protobuf's class definitions were not
split across the lite and full targets. Trying to fix that would involve
reorganizing a considerable amount of protobuf code, and I don't believe that's
necessary.

+  #if defined(_MSC_VER)
+    #ifdef LIBPROTOBUF_EXPORTS
+      #define LIBPROTOBUF_EXPORT __declspec(dllexport)
+    #else
+      #define LIBPROTOBUF_EXPORT __declspec(dllimport)
+    #endif
+    #ifdef LIBPROTOC_EXPORTS
+      #define LIBPROTOC_EXPORT   __declspec(dllexport)
+    #else
+      #define LIBPROTOC_EXPORT   __declspec(dllimport)
+    #endif
+  #else  // defined(_MSC_VER)
+    #ifdef LIBPROTOBUF_EXPORTS
+      #define LIBPROTOBUF_EXPORT __attribute__((visibility("default")))
+    #else
+      #define LIBPROTOBUF_EXPORT
+    #endif
+    #ifdef LIBPROTOC_EXPORTS
+      #define LIBPROTOC_EXPORT   __attribute__((visibility("default")))
+    #else
+      #define LIBPROTOC_EXPORT
+    #endif
   #endif
-  #ifdef LIBPROTOC_EXPORTS
-    #define LIBPROTOC_EXPORT   __declspec(dllexport)
-  #else
-    #define LIBPROTOC_EXPORT   __declspec(dllimport)
-  #endif
-#else
+#else  // defined(COMPONENT_BUILD) && defined(PROTOBUF_USE_DLLS)
   #define LIBPROTOBUF_EXPORT
   #define LIBPROTOC_EXPORT
 #endif