Restore LLVM-style static registry instantiation

Author: SineStriker

include/stdcorelib/support/staticregistry.h

@@ -271,15 +271,19 @@ namespace stdc {
 /// plugin arrangement is the host. \a EXPORT is what makes the list reachable from a plugin:
 /// \c __declspec(dllexport) on Windows, or nothing on the platforms where \c -rdynamic on the
 /// host is what does it.
+/// Since the macro defines the primary template's storage, use it only once in a translation
+/// unit; instantiate unrelated registry types in separate translation units.
 /// Both of these have to sit where they can name stdc, which is the global scope or inside stdc
 /// itself. Naming it rather than reopening it is what makes writing them anywhere else say so:
 /// the compiler answers "in namespace X, which does not enclose namespace stdc" instead of
 /// failing somewhere inside this header.
 #define STDC_INSTANTIATE_STATIC_REGISTRY_EXPORT(TYPE, EXPORT)                                      \
-    template <>                                                                                    \
-    typename ::stdc::StaticRegistry<TYPE>::Node * ::stdc::StaticRegistry<TYPE>::_head = nullptr;   \
-    template <>                                                                                    \
-    typename ::stdc::StaticRegistry<TYPE>::Node * ::stdc::StaticRegistry<TYPE>::_tail = nullptr;   \
+    template <class T, class Traits>                                                               \
+    typename ::stdc::StaticRegistry<T, Traits>::Node *                                             \
+        ::stdc::StaticRegistry<T, Traits>::_head = nullptr;                                        \
+    template <class T, class Traits>                                                               \
+    typename ::stdc::StaticRegistry<T, Traits>::Node *                                             \
+        ::stdc::StaticRegistry<T, Traits>::_tail = nullptr;                                        \
     template class EXPORT ::stdc::StaticRegistry<TYPE>;
 
 /// Defines the storage for a \c StaticRegistry over \a TYPE, undecorated.

tests/auto/support/test_staticregistry.cpp

@@ -46,28 +46,9 @@ namespace {
         int _channels;
     };
 
-    struct Descriptor {
-        int value;
-    };
-
-}
-
-namespace stdc {
-
-    template <>
-    struct static_registry_traits<Descriptor> {
-        using result_type = Descriptor;
-
-        template <class V>
-        static result_type construct() {
-            return V();
-        }
-    };
-
 }
 
 STDC_INSTANTIATE_STATIC_REGISTRY(Codec)
-STDC_INSTANTIATE_STATIC_REGISTRY(Descriptor)
 
 namespace {
 
@@ -84,10 +65,6 @@ namespace {
         return std::make_unique<PcmCodec>(44100, 2);
     });
 
-    using DescriptorRegistry = StaticRegistry<Descriptor>;
-    DescriptorRegistry::AddFactory descriptor_entry("answer", "",
-                                                    []() -> Descriptor { return {42}; });
-
 }
 
 BOOST_AUTO_TEST_SUITE(test_staticregistry)
@@ -138,9 +115,4 @@ BOOST_AUTO_TEST_CASE(test_factory_entry) {
     BOOST_CHECK_EQUAL(codec->id(), "pcm-44100-2"); // the arguments survived
 }
 
-BOOST_AUTO_TEST_CASE(test_value_result) {
-    const auto descriptor = DescriptorRegistry::begin()->instantiate();
-    BOOST_CHECK_EQUAL(descriptor.value, 42);
-}
-
 BOOST_AUTO_TEST_SUITE_END()

tests/auto/support/test_staticregistry_traits.cpp

@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: MIT
+
+#include <stdcorelib/support/staticregistry.h>
+
+#include <boost/test/unit_test.hpp>
+
+namespace {
+
+    struct Descriptor {
+        int value;
+    };
+
+}
+
+namespace stdc {
+
+    template <>
+    struct static_registry_traits<Descriptor> {
+        using result_type = Descriptor;
+
+        template <class V>
+        static result_type construct() {
+            return V();
+        }
+    };
+
+}
+
+STDC_INSTANTIATE_STATIC_REGISTRY(Descriptor)
+
+namespace {
+
+    using DescriptorRegistry = stdc::StaticRegistry<Descriptor>;
+    DescriptorRegistry::AddFactory descriptor_entry("answer", "",
+                                                     []() -> Descriptor { return {42}; });
+
+}
+
+BOOST_AUTO_TEST_SUITE(test_staticregistry_traits)
+
+BOOST_AUTO_TEST_CASE(test_value_result) {
+    const auto descriptor = DescriptorRegistry::begin()->instantiate();
+    BOOST_CHECK_EQUAL(descriptor.value, 42);
+}
+
+BOOST_AUTO_TEST_SUITE_END()