Cherry-pick of df71972: Simplify template exporting macros (#7539)

* Cherry-pick of df71972: Simplify template exporting macros * Fix macro usage
protocolbuffers · May 21, 2020 · 29de97c · 29de97c
1 parent a37cc13
commit 29de97c
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Showing 5 changed files with 32 additions and 210 deletions.
diff --git a/src/google/protobuf/parse_context.h b/src/google/protobuf/parse_context.h
@@ -744,7 +744,7 @@ PROTOBUF_EXPORT PROTOBUF_MUST_USE_RESULT const char* PackedEnumParser(
     void* object, const char* ptr, ParseContext* ctx);
 
 template <typename T>
-PROTOBUF_EXPORT_TEMPLATE_DEFINE(PROTOBUF_EXPORT)
+PROTOBUF_EXPORT_TEMPLATE_DEFINE
 PROTOBUF_MUST_USE_RESULT const
     char* PackedEnumParser(void* object, const char* ptr, ParseContext* ctx,
                            bool (*is_valid)(int), InternalMetadata* metadata,
@@ -760,7 +760,7 @@ PROTOBUF_MUST_USE_RESULT const
 }
 
 template <typename T>
-PROTOBUF_EXPORT_TEMPLATE_DEFINE(PROTOBUF_EXPORT)
+PROTOBUF_EXPORT_TEMPLATE_DEFINE
 PROTOBUF_MUST_USE_RESULT const
     char* PackedEnumParserArg(void* object, const char* ptr, ParseContext* ctx,
                               bool (*is_valid)(const void*, int),

diff --git a/src/google/protobuf/port_def.inc b/src/google/protobuf/port_def.inc
@@ -358,20 +358,28 @@
 #if defined(PROTOBUF_USE_DLLS)
   #if defined(_MSC_VER)
     #ifdef LIBPROTOBUF_EXPORTS
-    #define PROTOBUF_EXPORT __declspec(dllexport)
+      #define PROTOBUF_EXPORT __declspec(dllexport)
+      #define PROTOBUF_EXPORT_TEMPLATE_DECLARE
+      #define PROTOBUF_EXPORT_TEMPLATE_DEFINE __declspec(dllexport)
     #else
-    #define PROTOBUF_EXPORT __declspec(dllimport)
+      #define PROTOBUF_EXPORT __declspec(dllimport)
+      #define PROTOBUF_EXPORT_TEMPLATE_DECLARE
+      #define PROTOBUF_EXPORT_TEMPLATE_DEFINE __declspec(dllimport)
     #endif
     #ifdef LIBPROTOC_EXPORTS
-    #define PROTOC_EXPORT __declspec(dllexport)
+      #define PROTOC_EXPORT __declspec(dllexport)
     #else
-    #define PROTOC_EXPORT __declspec(dllimport)
+      #define PROTOC_EXPORT __declspec(dllimport)
     #endif
   #else  // defined(_MSC_VER)
     #ifdef LIBPROTOBUF_EXPORTS
       #define PROTOBUF_EXPORT __attribute__((visibility("default")))
+      #define PROTOBUF_EXPORT_TEMPLATE_DECLARE __attribute__((visibility("default")))
+      #define PROTOBUF_EXPORT_TEMPLATE_DEFINE
     #else
       #define PROTOBUF_EXPORT
+      #define PROTOBUF_EXPORT_TEMPLATE_DECLARE
+      #define PROTOBUF_EXPORT_TEMPLATE_DEFINE
     #endif
     #ifdef LIBPROTOC_EXPORTS
       #define PROTOC_EXPORT   __attribute__((visibility("default")))
@@ -382,168 +390,10 @@
 #else  // defined(PROTOBUF_USE_DLLS)
   #define PROTOBUF_EXPORT
   #define PROTOC_EXPORT
+  #define PROTOBUF_EXPORT_TEMPLATE_DECLARE
+  #define PROTOBUF_EXPORT_TEMPLATE_DEFINE
 #endif
 
-
-// This portion provides macros for using FOO_EXPORT macros with explicit
-// template instantiation declarations and definitions.
-// Generally, the FOO_EXPORT macros are used at declarations,
-// and GCC requires them to be used at explicit instantiation declarations,
-// but MSVC requires __declspec(dllexport) to be used at the explicit
-// instantiation definitions instead.
-
-// Usage
-//
-// In a header file, write:
-//
-//  extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE(FOO_EXPORT) foo<bar>;
-//
-// In a source file, write:
-//
-//  template class PROTOBUF_EXPORT_TEMPLATE_DEFINE(FOO_EXPORT) foo<bar>;
-//
-// Where FOO_EXPORT is either PROTOBUF_EXPORT or PROTOC_EXPORT
-
-// Implementation notes
-//
-// The implementation of these macros uses some subtle macro semantics to
-// detect what the provided FOO_EXPORT value was defined as and then
-// to dispatch to appropriate macro definitions.  Unfortunately,
-// MSVC's C preprocessor is rather non-compliant and requires special
-// care to make it work.
-//
-// Issue 1.
-//
-//   #define F(x)
-//   F()
-//
-// MSVC emits warning C4003 ("not enough actual parameters for macro
-// 'F'), even though it's a valid macro invocation.  This affects the
-// macros below that take just an "export" parameter, because export
-// may be empty.
-//
-// As a workaround, we can add a dummy parameter and arguments:
-//
-//   #define F(x,_)
-//   F(,)
-//
-// Issue 2.
-//
-//   #define F(x) G##x
-//   #define Gj() ok
-//   F(j())
-//
-// The correct replacement for "F(j())" is "ok", but MSVC replaces it
-// with "Gj()".  As a workaround, we can pass the result to an
-// identity macro to force MSVC to look for replacements again.  (This
-// is why PROTOBUF_EXPORT_TEMPLATE_STYLE_3 exists.)
-
-#define PROTOBUF_EXPORT_TEMPLATE_DECLARE(export) \
-  PROTOBUF_EXPORT_TEMPLATE_INVOKE( \
-    DECLARE, PROTOBUF_EXPORT_TEMPLATE_STYLE(export, ), export)
-#define PROTOBUF_EXPORT_TEMPLATE_DEFINE(export) \
-  PROTOBUF_EXPORT_TEMPLATE_INVOKE( \
-    DEFINE, PROTOBUF_EXPORT_TEMPLATE_STYLE(export, ), export)
-
-// INVOKE is an internal helper macro to perform parameter replacements
-// and token pasting to chain invoke another macro.  E.g.,
-//     PROTOBUF_EXPORT_TEMPLATE_INVOKE(DECLARE, DEFAULT, FOO_EXPORT)
-// will export to call
-//     PROTOBUF_EXPORT_TEMPLATE_DECLARE_DEFAULT(FOO_EXPORT, )
-// (but with FOO_EXPORT expanded too).
-#define PROTOBUF_EXPORT_TEMPLATE_INVOKE(which, style, export) \
-  PROTOBUF_EXPORT_TEMPLATE_INVOKE_2(which, style, export)
-#define PROTOBUF_EXPORT_TEMPLATE_INVOKE_2(which, style, export) \
-  PROTOBUF_EXPORT_TEMPLATE_##which##_##style(export, )
-
-// Default style is to apply the FOO_EXPORT macro at declaration sites.
-#define PROTOBUF_EXPORT_TEMPLATE_DECLARE_DEFAULT(export, _) export
-#define PROTOBUF_EXPORT_TEMPLATE_DEFINE_DEFAULT(export, _)
-
-// The "MSVC hack" style is used when FOO_EXPORT is defined
-// as __declspec(dllexport), which MSVC requires to be used at
-// definition sites instead.
-#define PROTOBUF_EXPORT_TEMPLATE_DECLARE_MSVC_HACK(export, _)
-#define PROTOBUF_EXPORT_TEMPLATE_DEFINE_MSVC_HACK(export, _) export
-
-// PROTOBUF_EXPORT_TEMPLATE_STYLE is an internal helper macro that identifies
-// which export style needs to be used for the provided FOO_EXPORT macro
-// definition.  "", "__attribute__(...)", and "__declspec(dllimport)" are
-// mapped to "DEFAULT"; while "__declspec(dllexport)" is mapped to "MSVC_HACK".
-//
-// It's implemented with token pasting to transform the __attribute__ and
-// __declspec annotations into macro invocations.  E.g., if FOO_EXPORT is
-// defined as "__declspec(dllimport)", it undergoes the following sequence of
-// macro substitutions:
-//     PROTOBUF_EXPORT_TEMPLATE_STYLE(FOO_EXPORT, )
-//     PROTOBUF_EXPORT_TEMPLATE_STYLE_2(__declspec(dllimport), )
-//     PROTOBUF_EXPORT_TEMPLATE_STYLE_3(
-//       PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH__declspec(dllimport))
-//     PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH__declspec(dllimport)
-//     PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH_DECLSPEC_dllimport
-//     DEFAULT
-#define PROTOBUF_EXPORT_TEMPLATE_STYLE(export, _) \
-  PROTOBUF_EXPORT_TEMPLATE_STYLE_2(export, )
-#define PROTOBUF_EXPORT_TEMPLATE_STYLE_2(export, _) \
-  PROTOBUF_EXPORT_TEMPLATE_STYLE_3(                 \
-      PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH_foj3FJo5StF0OvIzl7oMxA##export)
-#define PROTOBUF_EXPORT_TEMPLATE_STYLE_3(style) style
-
-// Internal helper macros for PROTOBUF_EXPORT_TEMPLATE_STYLE.
-//
-// XXX: C++ reserves all identifiers containing "__" for the implementation,
-// but "__attribute__" and "__declspec" already contain "__" and the token-paste
-// operator can only add characters; not remove them.  To minimize the risk of
-// conflict with implementations, we include "foj3FJo5StF0OvIzl7oMxA" (a random
-// 128-bit string, encoded in Base64) in the macro name.
-#define PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH_foj3FJo5StF0OvIzl7oMxA DEFAULT
-#define PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH_foj3FJo5StF0OvIzl7oMxA__attribute__(...) \
-  DEFAULT
-#define PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH_foj3FJo5StF0OvIzl7oMxA__declspec(arg) \
-  PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH_DECLSPEC_##arg
-
-// Internal helper macros for PROTOBUF_EXPORT_TEMPLATE_STYLE.
-#define PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH_DECLSPEC_dllexport MSVC_HACK
-#define PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH_DECLSPEC_dllimport DEFAULT
-
-// Sanity checks.
-//
-// PROTOBUF_EXPORT_TEMPLATE_TEST uses the same macro invocation pattern as
-// PROTOBUF_EXPORT_TEMPLATE_DECLARE and PROTOBUF_EXPORT_TEMPLATE_DEFINE do to
-// check that they're working correctly.  When they're working correctly, the
-// sequence of macro replacements should go something like:
-//
-//     PROTOBUF_EXPORT_TEMPLATE_TEST(DEFAULT, __declspec(dllimport));
-//
-//     static_assert(PROTOBUF_EXPORT_TEMPLATE_INVOKE(TEST_DEFAULT,
-//         PROTOBUF_EXPORT_TEMPLATE_STYLE(__declspec(dllimport), ),
-//         __declspec(dllimport)), "__declspec(dllimport)");
-//
-//     static_assert(PROTOBUF_EXPORT_TEMPLATE_INVOKE(TEST_DEFAULT,
-//         DEFAULT, __declspec(dllimport)), "__declspec(dllimport)");
-//
-//     static_assert(PROTOBUF_EXPORT_TEMPLATE_TEST_DEFAULT_DEFAULT(
-//         __declspec(dllimport)), "__declspec(dllimport)");
-//
-//     static_assert(true, "__declspec(dllimport)");
-//
-// When they're not working correctly, a syntax error should occur instead.
-#define PROTOBUF_EXPORT_TEMPLATE_TEST(want, export)                        \
-  static_assert(PROTOBUF_EXPORT_TEMPLATE_INVOKE(                           \
-                    TEST_##want, PROTOBUF_EXPORT_TEMPLATE_STYLE(export, ), \
-                    export), #export)
-#define PROTOBUF_EXPORT_TEMPLATE_TEST_DEFAULT_DEFAULT(...) true
-#define PROTOBUF_EXPORT_TEMPLATE_TEST_MSVC_HACK_MSVC_HACK(...) true
-
-PROTOBUF_EXPORT_TEMPLATE_TEST(DEFAULT, );
-PROTOBUF_EXPORT_TEMPLATE_TEST(DEFAULT, __attribute__((visibility("default"))));
-PROTOBUF_EXPORT_TEMPLATE_TEST(MSVC_HACK, __declspec(dllexport));
-PROTOBUF_EXPORT_TEMPLATE_TEST(DEFAULT, __declspec(dllimport));
-
-#undef PROTOBUF_EXPORT_TEMPLATE_TEST
-#undef PROTOBUF_EXPORT_TEMPLATE_TEST_DEFAULT_DEFAULT
-#undef PROTOBUF_EXPORT_TEMPLATE_TEST_MSVC_HACK_MSVC_HACK
-
 // Windows declares several inconvenient macro names.  We #undef them and then
 // restore them in port_undef.inc.
 #ifdef _MSC_VER

diff --git a/src/google/protobuf/port_undef.inc b/src/google/protobuf/port_undef.inc
@@ -69,19 +69,6 @@
 #undef PROTOBUF_EXPORT_TEMPLATE_DECLARE
 #undef PROTOBUF_EXPORT_TEMPLATE_DEFINE
 #undef PROTOBUF_ALIGNAS
-#undef PROTOBUF_EXPORT_TEMPLATE_INVOKE_2
-#undef PROTOBUF_EXPORT_TEMPLATE_DECLARE_DEFAULT
-#undef PROTOBUF_EXPORT_TEMPLATE_DEFINE_DEFAULT
-#undef PROTOBUF_EXPORT_TEMPLATE_DECLARE_MSVC_HACK
-#undef PROTOBUF_EXPORT_TEMPLATE_DEFINE_MSVC_HACK
-#undef PROTOBUF_EXPORT_TEMPLATE_STYLE
-#undef PROTOBUF_EXPORT_TEMPLATE_STYLE_2
-#undef PROTOBUF_EXPORT_TEMPLATE_STYLE_3
-#undef PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH_foj3FJo5StF0OvIzl7oMxA
-#undef PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH_foj3FJo5StF0OvIzl7oMxA__attribute__
-#undef PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH_foj3FJo5StF0OvIzl7oMxA__declspec
-#undef PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH_DECLSPEC_dllexport
-#undef PROTOBUF_EXPORT_TEMPLATE_STYLE_MATCH_DECLSPEC_dllimport
 #undef PROTOBUF_FINAL
 
 // Restore macro that may have been #undef'd in port_def.inc.

diff --git a/src/google/protobuf/repeated_field.cc b/src/google/protobuf/repeated_field.cc
@@ -123,22 +123,14 @@ MessageLite* RepeatedPtrFieldBase::AddWeak(const MessageLite* prototype) {
 }  // namespace internal
 
 
-template class PROTOBUF_EXPORT_TEMPLATE_DEFINE(PROTOBUF_EXPORT)
-    RepeatedField<bool>;
-template class PROTOBUF_EXPORT_TEMPLATE_DEFINE(PROTOBUF_EXPORT)
-    RepeatedField<int32>;
-template class PROTOBUF_EXPORT_TEMPLATE_DEFINE(PROTOBUF_EXPORT)
-    RepeatedField<uint32>;
-template class PROTOBUF_EXPORT_TEMPLATE_DEFINE(PROTOBUF_EXPORT)
-    RepeatedField<int64>;
-template class PROTOBUF_EXPORT_TEMPLATE_DEFINE(PROTOBUF_EXPORT)
-    RepeatedField<uint64>;
-template class PROTOBUF_EXPORT_TEMPLATE_DEFINE(PROTOBUF_EXPORT)
-    RepeatedField<float>;
-template class PROTOBUF_EXPORT_TEMPLATE_DEFINE(PROTOBUF_EXPORT)
-    RepeatedField<double>;
-template class PROTOBUF_EXPORT_TEMPLATE_DEFINE(PROTOBUF_EXPORT)
-    RepeatedPtrField<std::string>;
+template class PROTOBUF_EXPORT_TEMPLATE_DEFINE RepeatedField<bool>;
+template class PROTOBUF_EXPORT_TEMPLATE_DEFINE RepeatedField<int32>;
+template class PROTOBUF_EXPORT_TEMPLATE_DEFINE RepeatedField<uint32>;
+template class PROTOBUF_EXPORT_TEMPLATE_DEFINE RepeatedField<int64>;
+template class PROTOBUF_EXPORT_TEMPLATE_DEFINE RepeatedField<uint64>;
+template class PROTOBUF_EXPORT_TEMPLATE_DEFINE RepeatedField<float>;
+template class PROTOBUF_EXPORT_TEMPLATE_DEFINE RepeatedField<double>;
+template class PROTOBUF_EXPORT_TEMPLATE_DEFINE RepeatedPtrField<std::string>;
 
 }  // namespace protobuf
 }  // namespace google
diff --git a/src/google/protobuf/repeated_field.h b/src/google/protobuf/repeated_field.h
@@ -2816,21 +2816,14 @@ UnsafeArenaAllocatedRepeatedPtrFieldBackInserter(
 }
 
 // Extern declarations of common instantiations to reduce library bloat.
-extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE(PROTOBUF_EXPORT)
-    RepeatedField<bool>;
-extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE(PROTOBUF_EXPORT)
-    RepeatedField<int32>;
-extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE(PROTOBUF_EXPORT)
-    RepeatedField<uint32>;
-extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE(PROTOBUF_EXPORT)
-    RepeatedField<int64>;
-extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE(PROTOBUF_EXPORT)
-    RepeatedField<uint64>;
-extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE(PROTOBUF_EXPORT)
-    RepeatedField<float>;
-extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE(PROTOBUF_EXPORT)
-    RepeatedField<double>;
-extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE(PROTOBUF_EXPORT)
+extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE RepeatedField<bool>;
+extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE RepeatedField<int32>;
+extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE RepeatedField<uint32>;
+extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE RepeatedField<int64>;
+extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE RepeatedField<uint64>;
+extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE RepeatedField<float>;
+extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE RepeatedField<double>;
+extern template class PROTOBUF_EXPORT_TEMPLATE_DECLARE
     RepeatedPtrField<std::string>;
 
 }  // namespace protobuf