improve odr_violation doc

Author: jll63

doc/modules/ROOT/pages/BOOST_OPENMETHOD.adoc

@@ -45,7 +45,7 @@ For each virtual argument `arg`, the dispatch mechanism calls
 1. If `result` is a `virtual_ptr`, get the pointer to the v-table from it.
 2. If `boost_openmethod_vptr` can be called with `result` and a `Registry*`,
    and it returns a `vptr_type`, call it.
-3. Call `Registry::rtti::dynamic_vptr(result)`.
+3. Call `Registry::vptr::dynamic_vptr(result)`.
 
 
 The macro creates an ordinary inline function in the current scope, with the

doc/modules/ROOT/pages/BOOST_OPENMETHOD_ENABLE_RUNTIME_CHECKS.adoc

@@ -1,12 +1,13 @@
-= xref:macros.adoc[Macro] BOOST_OPENMETHOD_ENABLE_RUNTIME_CHECKS
 
-Enables runtime checks in default_registry.
+## BOOST_OPENMETHOD_ENABLE_RUNTIME_CHECKS
 
-== Synopsis
+Enables runtime checks in cpp:default_registry[].
+
+### Synopsis
 
 May be defined by a program before including
 `<boost/openmethod/default_registry.hpp>` to enable runtime checks.
 
-== Description
+### Description
 
 See cpp:default_registry[] for details.

include/boost/openmethod/default_registry.hpp

@@ -37,7 +37,8 @@ namespace boost::openmethod {
 //! including those pulled from libraries.
 struct default_registry
     : registry<
-          policies::std_rtti, policies::vptr_vector,
+          policies::std_rtti, policies
+          ::vptr_vector,
           policies::fast_perfect_hash, policies::default_error_handler,
           policies::stderr_output
 #ifdef BOOST_OPENMETHOD_ENABLE_RUNTIME_CHECKS

include/boost/openmethod/initialize.hpp

@@ -1575,7 +1575,7 @@ inline auto initialize(Options&&... options) {
         (std::is_base_of_v<detail::option_base, Options> && ...),
         "invalid option type");
 
-    if (odr_check<Registry>::count > 1) {
+    if (detail::odr_check<Registry>::count > 1) {
         // Multiple definitions of default_registry detected.
         // This indicates an ODR violation.
         // Signal a final_error using the error handler, then abort.

include/boost/openmethod/preamble.hpp

@@ -75,6 +75,11 @@ struct virtual_traits;
 //! Base class for all OpenMethod errors.
 struct openmethod_error {};
 
+//! One Definition Rule violation.
+//!
+//! This error is raised if the definition of @ref default_registry is
+//! inconsistent across translation units, due to misuse of
+//! [BOOST_OPENMETHOD_ENABLE_RUNTIME_CHECKS](../BOOST_OPENMETHOD_ENABLE_RUNTIME_CHECKS.html).
 struct odr_violation : openmethod_error {
     //! Write a description of the error to a stream.
     //! @tparam Registry The registry containing this policy.
@@ -87,6 +92,8 @@ struct odr_violation : openmethod_error {
     }
 };
 
+namespace detail {
+
 template<class Registry>
 struct odr_check {
     static std::size_t count;
@@ -98,14 +105,14 @@ struct odr_check {
     }
 };
 
-#ifndef BOOST_OPENMETHOD_IMPORT
 template<class Registry>
 std::size_t odr_check<Registry>::count;
 
 template<class Registry>
 template<class R>
 std::size_t odr_check<Registry>::inc = count++;
-#endif
+
+}
 
 //! Registry not initialized
 struct not_initialized : openmethod_error {
@@ -1048,7 +1055,6 @@ class registry : detail::registry_base {
         !std::is_same_v<policy<policies::indirect_vptr>, void>;
 };
 
-#ifndef BOOST_OPENMETHOD_IMPORT
 template<class... Policies>
 detail::class_catalog registry<Policies...>::classes;
 
@@ -1064,7 +1070,6 @@ bool registry<Policies...>::initialized;
 template<class... Policies>
 template<class Class>
 vptr_type registry<Policies...>::static_vptr;
-#endif
 
 template<class... Policies>
 void registry<Policies...>::require_initialized() {