🐛 Workaround GCC 12 bug

Problem:
- GCC 12 fails to compile flow nodes.

Solution:
- Persuade GCC that the run and log functions have linkage.

Author: elbeno

include/flow/step.hpp

@@ -23,6 +23,25 @@ struct rt_node {
                                      rt_node const &) -> bool = default;
 };
 
+namespace detail {
+template <typename Cond, typename F> constexpr auto run_func() -> void {
+    if (Cond{}) {
+        F{}();
+    }
+}
+
+template <typename ct_node, typename Cond, stdx::ct_string Type,
+          stdx::ct_string Name>
+constexpr auto log_func() -> void {
+    if (Cond{}) {
+        using log_spec_t = decltype(get_log_spec<ct_node>());
+        CIB_LOG(typename log_spec_t::flavor, log_spec_t::level, "flow.{}({})",
+                stdx::ct_string_to_type<Type, sc::string_constant>(),
+                stdx::ct_string_to_type<Name, sc::string_constant>());
+    }
+}
+} // namespace detail
+
 template <stdx::ct_string Type, stdx::ct_string Name,
           subgraph_identity Identity, typename Cond, typename F>
 struct ct_node {
@@ -40,19 +59,8 @@ struct ct_node {
     constexpr static auto condition = Cond{};
 
     constexpr operator rt_node() const {
-        return rt_node{
-            [] {
-                if (condition) {
-                    F{}();
-                }
-            },
-            [] {
-                if (condition) {
-                    using log_spec_t = decltype(get_log_spec<ct_node>());
-                    CIB_LOG(typename log_spec_t::flavor, log_spec_t::level,
-                            "flow.{}({})", type_t{}, name_t{});
-                }
-            }};
+        return rt_node{detail::run_func<Cond, F>,
+                       detail::log_func<ct_node, Cond, Type, Name>};
     }
 
     constexpr auto operator*() const {

test/flow/CMakeLists.txt

@@ -1,23 +1,13 @@
-if(${CMAKE_CXX_COMPILER_ID} STREQUAL "GNU" AND ${CMAKE_CXX_COMPILER_VERSION}
-                                               VERSION_LESS 13)
-    message(
-        WARNING
-            "GCC has a constexpr bug before version 13 that prevents flow steps from compiling. Not adding flow tests."
-    )
-else()
-    add_unit_test(
-        "flow_separate_actions_test"
-        CATCH2
-        FILES
-        "flow_cib_func.cpp"
-        "separate_actions.cpp"
-        LIBRARIES
-        warnings
-        cib)
+add_unit_test(
+    "flow_separate_actions_test"
+    CATCH2
+    FILES
+    "flow_cib_func.cpp"
+    "separate_actions.cpp"
+    LIBRARIES
+    warnings
+    cib)
 
-    add_tests(flow logging log_levels custom_log_levels)
-endif()
-
-add_tests(graph graph_builder)
+add_tests(flow graph graph_builder logging log_levels custom_log_levels)
 
 add_subdirectory(fail)