Change namespace scope constants from internal linkage to inline li…

…nkage to avoid potential ODR violations and code bloat.

Also, remove the now unnecessary redundant definition of class-scope `static
constexpr` variables.

PiperOrigin-RevId: 691426487

src/google/protobuf/compiler/cpp/enum.cc

@@ -170,8 +170,10 @@ void EnumGenerator::GenerateDefinition(io::Printer* p) {
 
         $dllexport_decl $bool $Msg_Enum$_IsValid(int value);
         $dllexport_decl $extern const uint32_t $Msg_Enum$_internal_data_[];
-        constexpr $Msg_Enum$ $Msg_Enum_Enum_MIN$ = static_cast<$Msg_Enum$>($kMin$);
-        constexpr $Msg_Enum$ $Msg_Enum_Enum_MAX$ = static_cast<$Msg_Enum$>($kMax$);
+        inline constexpr $Msg_Enum$ $Msg_Enum_Enum_MIN$ =
+            static_cast<$Msg_Enum$>($kMin$);
+        inline constexpr $Msg_Enum$ $Msg_Enum_Enum_MAX$ =
+            static_cast<$Msg_Enum$>($kMax$);
       )cc");
 
   if (generate_array_size_) {
@@ -180,7 +182,7 @@ void EnumGenerator::GenerateDefinition(io::Printer* p) {
                               "_ARRAYSIZE"))
                  .AnnotatedAs(enum_)},
             R"cc(
-              constexpr int $Msg_Enum_Enum_ARRAYSIZE$ = $kMax$ + 1;
+              inline constexpr int $Msg_Enum_Enum_ARRAYSIZE$ = $kMax$ + 1;
             )cc");
   }
 
@@ -548,45 +550,6 @@ void EnumGenerator::GenerateMethods(int idx, io::Printer* p) {
           }
         )cc");
   }
-
-  if (enum_->containing_type() != nullptr) {
-    // Before C++17, we must define the static constants which were
-    // declared in the header, to give the linker a place to put them.
-    // But MSVC++ pre-2015 and post-2017 (version 15.5+) insists that we not.
-    p->Emit(
-        {
-            {"Msg_", ClassName(enum_->containing_type(), false)},
-            {"constexpr_storage",
-             [&] {
-               for (int i = 0; i < enum_->value_count(); i++) {
-                 p->Emit({{"VALUE", EnumValueName(enum_->value(i))}},
-                         R"cc(
-                           constexpr $Msg_Enum$ $Msg_$::$VALUE$;
-                         )cc");
-               }
-             }},
-            {"array_size",
-             [&] {
-               if (generate_array_size_) {
-                 p->Emit(R"cc(
-                   constexpr int $Msg_$::$Enum$_ARRAYSIZE;
-                 )cc");
-               }
-             }},
-        },
-        R"(
-          #if (__cplusplus < 201703) && \
-            (!defined(_MSC_VER) || (_MSC_VER >= 1900 && _MSC_VER < 1912))
-          
-          $constexpr_storage$;
-          constexpr $Msg_Enum$ $Msg_$::$Enum$_MIN;
-          constexpr $Msg_Enum$ $Msg_$::$Enum$_MAX;
-          $array_size$;
-
-          #endif  // (__cplusplus < 201703) &&
-                  // (!defined(_MSC_VER) || (_MSC_VER >= 1900 && _MSC_VER < 1912))
-        )");
-  }
 }
 }  // namespace cpp
 }  // namespace compiler

src/google/protobuf/compiler/cpp/extension.cc

@@ -89,8 +89,13 @@ bool ExtensionGenerator::IsScoped() const {
 void ExtensionGenerator::GenerateDeclaration(io::Printer* p) const {
   auto var = p->WithVars(variables_);
   auto annotate = p->WithAnnotations({{"name", descriptor_}});
-
-  p->Emit({{"qualifier",
+  p->Emit({{"constant_qualifier",
+            // If this is a class member, it needs to be declared
+            //   `static constexpr`.
+            // Otherwise, it will be
+            //   `inline constexpr`.
+            IsScoped() ? "static" : ""},
+           {"id_qualifier",
             // If this is a class member, it needs to be declared "static".
             // Otherwise, it needs to be "extern".  In the latter case, it
             // also needs the DLL export/import specifier.
@@ -99,8 +104,9 @@ void ExtensionGenerator::GenerateDeclaration(io::Printer* p) const {
                 ? "extern"
                 : absl::StrCat(options_.dllexport_decl, " extern")}},
           R"cc(
-            static const int $constant_name$ = $number$;
-            $qualifier$ ::$proto_ns$::internal::ExtensionIdentifier<
+            inline $constant_qualifier $constexpr int $constant_name$ =
+                $number$;
+            $id_qualifier$ ::$proto_ns$::internal::ExtensionIdentifier<
                 $extendee$, ::$proto_ns$::internal::$type_traits$, $field_type$,
                 $packed$>
                 $name$;
@@ -147,32 +153,13 @@ void ExtensionGenerator::GenerateDefinition(io::Printer* p) {
                const std::string $default_str$($default_val$);
              )cc");
            }},
-          {"declare_const_var",
-           [&] {
-             if (!IsScoped()) return;
-             // Likewise, class members need to declare the field constant
-             // variable.
-             p->Emit(R"cc(
-#if !defined(_MSC_VER) || (_MSC_VER >= 1900 && _MSC_VER < 1912)
-               const int $scope$$constant_name$;
-#endif
-             )cc");
-           }},
-          {"define_extension_id",
-           [&] {
-             p->Emit(R"cc(
-               PROTOBUF_CONSTINIT$ dllexport_decl$
-                   PROTOBUF_ATTRIBUTE_INIT_PRIORITY2 ::_pbi::
-                       ExtensionIdentifier<$extendee$, ::_pbi::$type_traits$,
-                                           $field_type$, $packed$>
-                           $scoped_name$($constant_name$, $default_str$);
-             )cc");
-           }},
       },
       R"cc(
         $declare_default_str$;
-        $declare_const_var$;
-        $define_extension_id$;
+        PROTOBUF_CONSTINIT$ dllexport_decl$
+            PROTOBUF_ATTRIBUTE_INIT_PRIORITY2 ::_pbi::ExtensionIdentifier<
+                $extendee$, ::_pbi::$type_traits$, $field_type$, $packed$>
+                $scoped_name$($constant_name$, $default_str$);
       )cc");
 }