Add support for DLL exporting of generated code

New options: --export-symbol, --extern-symbol.

3 files changed, 29 insertions, 20 deletions

diff --git a/odb/relational/header.cxx b/odb/relational/header.cxx
index 543e1ac..ff2679e 100644
--- a/odb/relational/header.cxx
+++ b/odb/relational/header.cxx
@@ -52,8 +52,8 @@ traverse_object (type& c)
   // object_traits_impl
   //
   os << "template <>" << endl
-     << "class access::object_traits_impl< " << type << ", id_" << db <<
-    " >:"  << endl
+     << "class " << exp << "access::object_traits_impl< " << type << ", " <<
+    "id_" << db << " >:"  << endl
      << "  public access::object_traits< " << type << " >"
      << "{"
      << "public:" << endl;
@@ -680,8 +680,8 @@ traverse_view (type& c)
   // view_traits_impl
   //
   os << "template <>" << endl
-     << "class access::view_traits_impl< " << type << ", id_" <<
-    db << " >:" << endl
+     << "class " << exp << "access::view_traits_impl< " << type << ", " <<
+    "id_" << db << " >:" << endl
      << "  public access::view_traits< " << type << " >"
      << "{"
      << "public:" << endl;
@@ -834,9 +834,13 @@ traverse_composite (type& c)
   os << "// " << class_name (c) << endl
      << "//" << endl;
 
+  // While composite_value_traits is not used directly by user code, we
+  // still need to export it if the generated code for the same database
+  // is split into several DLLs.
+  //
   os << "template <>" << endl
-     << "class access::composite_value_traits< " << type << ", " <<
-    "id_" << db << " >"
+     << "class " << exp << "access::composite_value_traits< " << type <<
+    ", id_" << db << " >"
      << "{"
      << "public:" << endl;
 
diff --git a/odb/relational/header.hxx b/odb/relational/header.hxx
index 89ef664..3e0480f 100644
--- a/odb/relational/header.hxx
+++ b/odb/relational/header.hxx
@@ -747,8 +747,8 @@ namespace relational
           : id_image_member_ ("id_"),
             version_image_member_ ("version_"),
             discriminator_image_member_ ("discriminator_"),
-            query_columns_type_ (false, true),
-            pointer_query_columns_type_ (true, true)
+            query_columns_type_ (false, true, false),
+            pointer_query_columns_type_ (true, true, false)
       {
       }
 
@@ -758,8 +758,8 @@ namespace relational
             id_image_member_ ("id_"),
             version_image_member_ ("version_"),
             discriminator_image_member_ ("discriminator_"),
-            query_columns_type_ (false, true),
-            pointer_query_columns_type_ (true, true)
+            query_columns_type_ (false, true, false),
+            pointer_query_columns_type_ (true, true, false)
       {
       }
 
@@ -823,7 +823,8 @@ namespace relational
       typedef class2 base;
 
       class2 ()
-          : query_columns_type_ (false, true),
+          : query_columns_type_ (false, true, false),
+            query_columns_type_inst_ (false, false, true),
             view_query_columns_type_ (true)
       {
       }
@@ -831,7 +832,8 @@ namespace relational
       class2 (class_ const&)
           : root_context (), //@@ -Wextra
             context (),
-            query_columns_type_ (false, true),
+            query_columns_type_ (false, true, false),
+            query_columns_type_inst_ (false, false, true),
             view_query_columns_type_ (true)
       {
       }
@@ -855,19 +857,21 @@ namespace relational
       {
         if (options.generate_query ())
         {
-          bool has_ptr (has_a (c, test_pointer | include_base));
-
-          if (has_ptr)
-            os << "// " << class_name (c) << endl
-               << "//" << endl;
+          os << "// " << class_name (c) << endl
+             << "//" << endl;
 
           // query_columns
           //
           // If we don't have any pointers, then query_columns is generated
           // in pass 1 (see the comment in class1 for details).
           //
-          if (has_ptr)
+          if (has_a (c, test_pointer | include_base))
             query_columns_type_->traverse (c);
+
+          // Generate extern template declarations.
+          //
+          if (multi_dynamic)
+            query_columns_type_inst_->traverse (c);
         }
 
         // Move header comment out of if-block if adding any code here.
@@ -896,6 +900,7 @@ namespace relational
 
     private:
       instance<query_columns_type> query_columns_type_;
+      instance<query_columns_type> query_columns_type_inst_;
       instance<view_query_columns_type> view_query_columns_type_;
     };
 
diff --git a/odb/relational/source.hxx b/odb/relational/source.hxx
index ed5f0e3..610c545 100644
--- a/odb/relational/source.hxx
+++ b/odb/relational/source.hxx
@@ -3294,7 +3294,7 @@ namespace relational
       typedef class_ base;
 
       class_ ()
-          : query_columns_type_ (false, false),
+          : query_columns_type_ (false, false, false),
             view_query_columns_type_ (false),
             grow_base_ (index_),
             grow_member_ (index_),
@@ -3318,7 +3318,7 @@ namespace relational
       class_ (class_ const&)
           : root_context (), //@@ -Wextra
             context (),
-            query_columns_type_ (false, false),
+            query_columns_type_ (false, false, false),
             view_query_columns_type_ (false),
             grow_base_ (index_),
             grow_member_ (index_),