Rework module architecture

Now the target type and rule maps are in scopes (builtins -- in global
scope). We also now have the map of loaded modules in the root scope of
each project.

26 files changed, 671 insertions, 442 deletions

diff --git a/build/algorithm.cxx b/build/algorithm.cxx
index bec51aa..488bbb7 100644
--- a/build/algorithm.cxx
+++ b/build/algorithm.cxx
@@ -45,131 +45,148 @@ namespace build
     //
     t.prerequisite_targets.clear ();
 
+    size_t oi (a.operation () - 1); // Operation index in rule_map.
+    scope& bs (t.base_scope ());
+
     for (auto tt (&t.type ());
          tt != nullptr && !t.recipe (a);
          tt = tt->base)
     {
-      auto i (current_rules->find (tt->id));
+      // Search scopes outwards, stopping at the project root.
+      //
+      for (const scope* s (&bs);
+           s != nullptr;
+           s = s->root () ? global_scope : s->parent_scope ())
+      {
+        const rule_map& om (s->rules);
 
-      if (i == current_rules->end () || i->second.empty ())
-        continue; // No rules registered for this target type, try base.
+        if (om.size () <= oi)
+          continue; // No entry for this operation id.
 
-      const auto& rules (i->second); // Hint map.
+        const target_type_rule_map& ttm (om[oi]);
 
-      // @@ TODO
-      //
-      // Different rules can be used for different operations (update
-      // vs test is a good example). So, at some point, we will probably
-      // have to support a list of hints or even an operation-hint map
-      // (e.g., 'hint=cxx test=foo' if cxx supports the test operation
-      // but we want the foo rule instead). This is also the place where
-      // the '{build clean}=cxx' construct (which we currently do not
-      // support) can come handy.
-      //
-      // Also, ignore the hint (that is most likely ment for a different
-      // operation) if this is a unique match.
-      //
-      string hint;
-      auto rs (rules.size () == 1
-               ? make_pair (rules.begin (), rules.end ())
-               : rules.find_prefix (hint));
+        if (ttm.empty ())
+          continue; // Empty map for this operation id.
 
-      for (auto i (rs.first); i != rs.second; ++i)
-      {
-        const string& n (i->first);
-        const rule& ru (i->second);
+        auto i (ttm.find (tt->id));
 
-        match_result m;
-        {
-          auto g (
-            make_exception_guard (
-              [](action a, target& t, const string& n)
-              {
-                info << "while matching rule " << n << " to "
-                     << diag_do (a, t);
-              },
-              a, t, n));
+        if (i == ttm.end () || i->second.empty ())
+          continue; // No rules registered for this target type.
 
-          m = ru.match (a, t, hint);
-        }
+        const auto& rules (i->second); // Hint map.
+
+        // @@ TODO
+        //
+        // Different rules can be used for different operations (update
+        // vs test is a good example). So, at some point, we will probably
+        // have to support a list of hints or even an operation-hint map
+        // (e.g., 'hint=cxx test=foo' if cxx supports the test operation
+        // but we want the foo rule instead). This is also the place where
+        // the '{build clean}=cxx' construct (which we currently do not
+        // support) can come handy.
+        //
+        // Also, ignore the hint (that is most likely ment for a different
+        // operation) if this is a unique match.
+        //
+        string hint;
+        auto rs (rules.size () == 1
+                 ? make_pair (rules.begin (), rules.end ())
+                 : rules.find_prefix (hint));
 
-        if (m)
+        for (auto i (rs.first); i != rs.second; ++i)
         {
-          // Do the ambiguity test.
-          //
-          bool ambig (false);
+          const string& n (i->first);
+          const rule& ru (i->second);
 
-          diag_record dr;
+          match_result m;
+          {
+            auto g (
+              make_exception_guard (
+                [](action a, target& t, const string& n)
+                {
+                  info << "while matching rule " << n << " to "
+                       << diag_do (a, t);
+                },
+                a, t, n));
+
+            m = ru.match (a, t, hint);
+          }
 
-          for (++i; i != rs.second; ++i)
+          if (m)
           {
-            const string& n1 (i->first);
-            const rule& ru1 (i->second);
+            // Do the ambiguity test.
+            //
+            bool ambig (false);
 
-            match_result m1;
-            {
-              auto g (
-                make_exception_guard (
-                  [](action a, target& t, const string& n1)
-                  {
-                    info << "while matching rule " << n1 << " to "
-                         << diag_do (a, t);
-                  },
-                  a, t, n1));
-
-              m1 = ru1.match (a, t, hint);
-            }
+            diag_record dr;
 
-            if (m1)
+            for (++i; i != rs.second; ++i)
             {
-              if (!ambig)
+              const string& n1 (i->first);
+              const rule& ru1 (i->second);
+
+              match_result m1;
               {
-                dr << fail << "multiple rules matching " << diag_doing (a, t)
-                   << info << "rule " << n << " matches";
-                ambig = true;
+                auto g (
+                  make_exception_guard (
+                    [](action a, target& t, const string& n1)
+                    {
+                      info << "while matching rule " << n1 << " to "
+                           << diag_do (a, t);
+                    },
+                    a, t, n1));
+
+                m1 = ru1.match (a, t, hint);
               }
 
-              dr << info << "rule " << n1 << " also matches";
+              if (m1)
+              {
+                if (!ambig)
+                {
+                  dr << fail << "multiple rules matching " << diag_doing (a, t)
+                     << info << "rule " << n << " matches";
+                  ambig = true;
+                }
+
+                dr << info << "rule " << n1 << " also matches";
+              }
             }
-          }
 
-          if (!ambig)
-          {
-            if (apply)
-            {
-              auto g (
-                make_exception_guard (
-                  [](action a, target& t, const string& n)
-                  {
-                    info << "while applying rule " << n << " to "
-                         << diag_do (a, t);
-                  },
-                  a, t, n));
-
-              t.recipe (a, ru.apply (a, t, m));
-              break;
-            }
-            else
+            if (!ambig)
             {
-              r.first = &ru;
-              r.second = m;
+              if (apply)
+              {
+                auto g (
+                  make_exception_guard (
+                    [](action a, target& t, const string& n)
+                    {
+                      info << "while applying rule " << n << " to "
+                           << diag_do (a, t);
+                    },
+                    a, t, n));
+
+                t.recipe (a, ru.apply (a, t, m));
+              }
+              else
+              {
+                r.first = &ru;
+                r.second = m;
+              }
+
               return r;
             }
+            else
+              dr << info << "use rule hint to disambiguate this match";
           }
-          else
-            dr << info << "use rule hint to disambiguate this match";
         }
       }
     }
 
-    if (!t.recipe (a))
-    {
-      diag_record dr;
-      dr << fail << "no rule to " << diag_do (a, t);
+    diag_record dr;
+    dr << fail << "no rule to " << diag_do (a, t);
 
-      if (verb < 3)
-        dr << info << "re-run with --verbose 3 for more information";
-    }
+    if (verb < 3)
+      dr << info << "re-run with --verbose 3 for more information";
 
     return r;
   }
diff --git a/build/b.cxx b/build/b.cxx
index d7fb9d3..0291729 100644
--- a/build/b.cxx
+++ b/build/b.cxx
@@ -77,15 +77,8 @@ namespace build
 }
 
 #include <build/config/module>
-
-#include <build/bin/target> //@@ tmp
-#include <build/bin/rule>   //@@ tmp
 #include <build/bin/module>
-
-#include <build/cxx/target> //@@ tmp
-#include <build/cxx/rule>   //@@ tmp
 #include <build/cxx/module>
-
 #include <build/cli/module>
 
 using namespace build;
@@ -131,91 +124,12 @@ main (int argc, char* argv[])
     //
     tzset ();
 
-    // Register modules.
-    //
-    modules["config"] = &config::init;
-    modules["bin"] = &bin::init;
-    modules["cxx"] = &cxx::init;
-    modules["cli"] = &cli::init;
-
-    // Register target types.
-    //
-    target_types.insert (file::static_type);
-    target_types.insert (dir::static_type);
-    target_types.insert (fsdir::static_type);
-
-    target_types.insert (bin::obja::static_type);
-    target_types.insert (bin::objso::static_type);
-    target_types.insert (bin::obj::static_type);
-    target_types.insert (bin::exe::static_type);
-    target_types.insert (bin::liba::static_type);
-    target_types.insert (bin::libso::static_type);
-    target_types.insert (bin::lib::static_type);
-
-    target_types.insert (cxx::h::static_type);
-    target_types.insert (cxx::c::static_type);
-
-    target_types.insert (cxx::cxx::static_type);
-    target_types.insert (cxx::hxx::static_type);
-    target_types.insert (cxx::ixx::static_type);
-    target_types.insert (cxx::txx::static_type);
-
-    // Register rules.
+    // Register builtin modules.
     //
-    bin::obj_rule obj_rule;
-    bin::lib_rule lib_rule;
-    {
-      using namespace bin;
-
-      rules[default_id][typeid (obj)].emplace ("bin.obj", obj_rule);
-      rules[update_id][typeid (obj)].emplace ("bin.obj", obj_rule);
-      rules[clean_id][typeid (obj)].emplace ("bin.obj", obj_rule);
-
-      rules[default_id][typeid (lib)].emplace ("bin.lib", lib_rule);
-      rules[update_id][typeid (lib)].emplace ("bin.lib", lib_rule);
-      rules[clean_id][typeid (lib)].emplace ("bin.lib", lib_rule);
-    }
-
-    cxx::compile cxx_compile;
-    cxx::link cxx_link;
-    {
-      using namespace bin;
-
-      rules[default_id][typeid (obja)].emplace ("cxx.gnu.compile", cxx_compile);
-      rules[update_id][typeid (obja)].emplace ("cxx.gnu.compile", cxx_compile);
-      rules[clean_id][typeid (obja)].emplace ("cxx.gnu.compile", cxx_compile);
-
-      rules[default_id][typeid (objso)].emplace ("cxx.gnu.compile", cxx_compile);
-      rules[update_id][typeid (objso)].emplace ("cxx.gnu.compile", cxx_compile);
-      rules[clean_id][typeid (objso)].emplace ("cxx.gnu.compile", cxx_compile);
-
-      rules[default_id][typeid (exe)].emplace ("cxx.gnu.link", cxx_link);
-      rules[update_id][typeid (exe)].emplace ("cxx.gnu.link", cxx_link);
-      rules[clean_id][typeid (exe)].emplace ("cxx.gnu.link", cxx_link);
-
-      rules[default_id][typeid (liba)].emplace ("cxx.gnu.link", cxx_link);
-      rules[update_id][typeid (liba)].emplace ("cxx.gnu.link", cxx_link);
-      rules[clean_id][typeid (liba)].emplace ("cxx.gnu.link", cxx_link);
-
-      rules[default_id][typeid (libso)].emplace ("cxx.gnu.link", cxx_link);
-      rules[update_id][typeid (libso)].emplace ("cxx.gnu.link", cxx_link);
-      rules[clean_id][typeid (libso)].emplace ("cxx.gnu.link", cxx_link);
-    }
-
-    dir_rule dir_r;
-    rules[default_id][typeid (dir)].emplace ("dir", dir_r);
-    rules[update_id][typeid (dir)].emplace ("dir", dir_r);
-    rules[clean_id][typeid (dir)].emplace ("dir", dir_r);
-
-    fsdir_rule fsdir_r;
-    rules[default_id][typeid (fsdir)].emplace ("fsdir", fsdir_r);
-    rules[update_id][typeid (fsdir)].emplace ("fsdir", fsdir_r);
-    rules[clean_id][typeid (fsdir)].emplace ("fsdir", fsdir_r);
-
-    file_rule file_r;
-    rules[default_id][typeid (file)].emplace ("file", file_r);
-    rules[update_id][typeid (file)].emplace ("file", file_r);
-    rules[clean_id][typeid (file)].emplace ("file", file_r);
+    builtin_modules["config"] = &config::config_init;
+    builtin_modules["bin"] = &bin::bin_init;
+    builtin_modules["cxx"] = &cxx::cxx_init;
+    builtin_modules["cli"] = &cli::cli_init;
 
     // Figure out work and home directories.
     //
@@ -379,7 +293,7 @@ main (int argc, char* argv[])
 
             // Handle a few common cases as special: empty name, '.',
             // '..', as well as dir{foo/bar} (without trailing '/').
-            // This code must be consistent with target_type_map::find().
+            // This code must be consistent with find_target_type().
             //
             if (v.empty () || v == "." || v == ".." || tn.type == "dir")
               out_base = dir_path (v);
@@ -744,7 +658,6 @@ main (int argc, char* argv[])
               current_mif = mif;
               current_oif = oif;
               current_mode = oif->mode;
-              current_rules = &rules[oid];
             }
             //
             // Similar to meta-operations, check that all the targets in
@@ -787,8 +700,10 @@ main (int argc, char* argv[])
           // operation batch.
           //
           {
+            scope& bs (scopes.find (out_base));
+
             const string* e;
-            const target_type* ti (target_types.find (tn, e));
+            const target_type* ti (bs.find_target_type (tn, e));
 
             if (ti == nullptr)
               fail (l) << "unknown target type " << tn.type;
diff --git a/build/bin/module b/build/bin/module
index e09e742..b87a0b0 100644
--- a/build/bin/module
+++ b/build/bin/module
@@ -12,8 +12,8 @@ namespace build
 {
   namespace bin
   {
-    void
-    init (scope&, scope&, const location&);
+    extern "C" void
+    bin_init (scope&, scope&, const location&, std::unique_ptr<module>&, bool);
   }
 }
 
diff --git a/build/bin/module.cxx b/build/bin/module.cxx
index 3775302..b2374ff 100644
--- a/build/bin/module.cxx
+++ b/build/bin/module.cxx
@@ -10,39 +10,70 @@
 
 #include <build/config/utility>
 
+#include <build/bin/rule>
+#include <build/bin/target>
+
 using namespace std;
 
 namespace build
 {
   namespace bin
   {
+    static obj_rule obj_;
+    static lib_rule lib_;
+
     // Default config.bin.*.lib values.
     //
     static const list_value exe_lib (names {name ("shared"), name ("static")});
     static const list_value liba_lib ("static");
     static const list_value libso_lib ("shared");
 
-    void
-    init (scope& root, scope& base, const location& l)
+    extern "C" void
+    bin_init (scope& root,
+              scope& base,
+              const location& l,
+              std::unique_ptr<module>&,
+              bool)
     {
-      //@@ TODO: avoid multiple inits (generally, for modules).
-      //
       tracer trace ("bin::init");
+      level4 ([&]{trace << "for " << base.path ();});
+
+      // Register target types.
+      //
+      {
+        auto& tts (base.target_types);
+        tts.insert<obja>  ();
+        tts.insert<objso> ();
+        tts.insert<obj>   ();
+        tts.insert<exe>   ();
+        tts.insert<liba>  ();
+        tts.insert<libso> ();
+        tts.insert<lib>   ();
+      }
 
-      //@@ Should it be this way?
+      // Register rules.
       //
-      if (&root != &base)
-        fail (l) << "bin module must be initialized in project root scope";
+      {
+        auto& rs (base.rules);
 
-      //@@ TODO: need to register target types, rules here instead of main().
+        rs.insert<obj> (default_id, "bin.obj", obj_);
+        rs.insert<obj> (update_id, "bin.obj", obj_);
+        rs.insert<obj> (clean_id, "bin.obj", obj_);
 
-      const dir_path& out_root (root.path ());
-      level4 ([&]{trace << "for " << out_root;});
+        rs.insert<lib> (default_id, "bin.lib", lib_);
+        rs.insert<lib> (update_id, "bin.lib", lib_);
+        rs.insert<lib> (clean_id, "bin.lib", lib_);
+      }
 
       // Configure.
       //
       using config::required;
 
+      // The idea here is as follows: if we already have one of
+      // the bin.* variables set, then we assume this is static
+      // project configuration and don't bother setting the
+      // corresponding config.bin.* variable.
+      //
       //@@ Need to validate the values. Would be more efficient
       //   to do it once on assignment than every time on query.
       //   Custom var type?
@@ -51,7 +82,7 @@ namespace build
       // config.bin.lib
       //
       {
-        auto v (root.vars.assign ("bin.lib"));
+        auto v (base.vars.assign ("bin.lib"));
         if (!v)
           v = required (root, "config.bin.lib", "shared").first;
       }
@@ -59,7 +90,7 @@ namespace build
       // config.bin.exe.lib
       //
       {
-        auto v (root.vars.assign ("bin.exe.lib"));
+        auto v (base.vars.assign ("bin.exe.lib"));
         if (!v)
           v = required (root, "config.bin.exe.lib", exe_lib).first;
       }
@@ -67,7 +98,7 @@ namespace build
       // config.bin.liba.lib
       //
       {
-        auto v (root.vars.assign ("bin.liba.lib"));
+        auto v (base.vars.assign ("bin.liba.lib"));
         if (!v)
           v = required (root, "config.bin.liba.lib", liba_lib).first;
       }
@@ -75,7 +106,7 @@ namespace build
       // config.bin.libso.lib
       //
       {
-        auto v (root.vars.assign ("bin.libso.lib"));
+        auto v (base.vars.assign ("bin.libso.lib"));
         if (!v)
           v = required (root, "config.bin.libso.lib", libso_lib).first;
       }
diff --git a/build/cli/module b/build/cli/module
index c2bc0ab..cf6258f 100644
--- a/build/cli/module
+++ b/build/cli/module
@@ -12,8 +12,8 @@ namespace build
 {
   namespace cli
   {
-    void
-    init (scope&, scope&, const location&);
+    extern "C" void
+    cli_init (scope&, scope&, const location&, std::unique_ptr<module>&, bool);
   }
 }
 
diff --git a/build/cli/module.cxx b/build/cli/module.cxx
index d3fa87d..c1d0aab 100644
--- a/build/cli/module.cxx
+++ b/build/cli/module.cxx
@@ -13,7 +13,6 @@
 #include <build/diagnostics>
 
 #include <build/cxx/target>
-#include <build/cxx/module>
 
 #include <build/config/utility>
 
@@ -29,54 +28,62 @@ namespace build
   {
     static compile compile_;
 
-    void
-    init (scope& root, scope& base, const location& l)
+    extern "C" void
+    cli_init (scope& root,
+              scope& base,
+              const location& l,
+              std::unique_ptr<module>&,
+              bool first)
     {
-      //@@ TODO: avoid multiple inits (generally, for modules).
-      //
       tracer trace ("cli::init");
+      level4 ([&]{trace << "for " << base.path ();});
 
-      //@@ Should it be this way?
+      // Make sure the cxx module has been loaded since we need its
+      // targets types (?xx{}). Note that we don't try to load it
+      // ourselves because of the non-trivial variable merging
+      // semantics. So it is better to let the user load cxx
+      // explicitly.
       //
-      if (&root != &base)
-        fail (l) << "cli module must be initialized in project root scope";
+      if (base.find_target_type ("cxx") == nullptr)
+        fail (l) << "cxx module must be initialized before cli";
 
-      // Initialize the cxx module. We need its targets types (?xx{}).
-      // @@ Or better require it?
+      // Register target types.
       //
-      cxx::init (root, base, l);
-
-      const dir_path& out_root (root.path ());
-      level4 ([&]{trace << "for " << out_root;});
+      {
+        auto& tts (base.target_types);
 
-      // Register our target types.
-      //
-      target_types.insert (cli::static_type);
-      target_types.insert (cli_cxx::static_type);
+        tts.insert<cli> ();
+        tts.insert<cli_cxx> ();
+      }
 
       // Register our rules.
       //
-      rules[default_id][typeid (cli_cxx)].emplace ("cli.compile", compile_);
-      rules[update_id][typeid (cli_cxx)].emplace ("cli.compile", compile_);
-      rules[clean_id][typeid (cli_cxx)].emplace ("cli.compile", compile_);
+      {
+        auto& rs (base.rules);
 
-      rules[default_id][typeid (cxx::cxx)].emplace ("cli.compile", compile_);
-      rules[update_id][typeid (cxx::cxx)].emplace ("cli.compile", compile_);
-      rules[clean_id][typeid (cxx::cxx)].emplace ("cli.compile", compile_);
+        rs.insert<cli_cxx> (default_id, "cli.compile", compile_);
+        rs.insert<cli_cxx> (update_id, "cli.compile", compile_);
+        rs.insert<cli_cxx> (clean_id, "cli.compile", compile_);
 
-      rules[default_id][typeid (cxx::hxx)].emplace ("cli.compile", compile_);
-      rules[update_id][typeid (cxx::hxx)].emplace ("cli.compile", compile_);
-      rules[clean_id][typeid (cxx::hxx)].emplace ("cli.compile", compile_);
+        rs.insert<cxx::hxx> (default_id, "cli.compile", compile_);
+        rs.insert<cxx::hxx> (update_id, "cli.compile", compile_);
+        rs.insert<cxx::hxx> (clean_id, "cli.compile", compile_);
 
-      rules[default_id][typeid (cxx::ixx)].emplace ("cli.compile", compile_);
-      rules[update_id][typeid (cxx::ixx)].emplace ("cli.compile", compile_);
-      rules[clean_id][typeid (cxx::ixx)].emplace ("cli.compile", compile_);
+        rs.insert<cxx::cxx> (default_id, "cli.compile", compile_);
+        rs.insert<cxx::cxx> (update_id, "cli.compile", compile_);
+        rs.insert<cxx::cxx> (clean_id, "cli.compile", compile_);
+
+        rs.insert<cxx::ixx> (default_id, "cli.compile", compile_);
+        rs.insert<cxx::ixx> (update_id, "cli.compile", compile_);
+        rs.insert<cxx::ixx> (clean_id, "cli.compile", compile_);
+      }
 
       // Configure.
       //
 
       // config.cli
       //
+      if (first)
       {
         auto r (config::required (root, "config.cli", "cli"));
 
@@ -132,10 +139,11 @@ namespace build
       // config.cli.options
       //
       // This one is optional. We also merge it into the corresponding
-      // cli.* variables.
+      // cli.* variables. See the cxx module for more information on
+      // this merging semantics and some of its tricky aspects.
       //
       if (auto* v = config::optional<list_value> (root, "config.cli.options"))
-        root.append ("cli.options") += *v;
+        base.assign ("cli.options") += *v;
     }
   }
 }
diff --git a/build/config/module b/build/config/module
index 4ab3e7e..58d9814 100644
--- a/build/config/module
+++ b/build/config/module
@@ -12,8 +12,9 @@ namespace build
 {
   namespace config
   {
-    void
-    init (scope&, scope&, const location&);
+    extern "C" void
+    config_init (
+      scope&, scope&, const location&, std::unique_ptr<module>&, bool);
   }
 }
 
diff --git a/build/config/module.cxx b/build/config/module.cxx
index 7ac9071..237547c 100644
--- a/build/config/module.cxx
+++ b/build/config/module.cxx
@@ -23,16 +23,23 @@ namespace build
     //
     static const path config_file ("build/config.build");
 
-    void
-    init (scope& root, scope& base, const location& l)
+    extern "C" void
+    config_init (scope& root,
+                 scope& base,
+                 const location& l,
+                 std::unique_ptr<module>&,
+                 bool first)
     {
-      //@@ TODO: avoid multiple inits (generally, for modules).
-      //
-
       tracer trace ("config::init");
 
       if (&root != &base)
-        fail (l) << "config module must be initialized in project root scope";
+        fail (l) << "config module must be initialized in bootstrap.build";
+
+      if (!first)
+      {
+        warn (l) << "multiple config module initializations";
+        return;
+      }
 
       const dir_path& out_root (root.path ());
       level4 ([&]{trace << "for " << out_root;});
diff --git a/build/config/operation.cxx b/build/config/operation.cxx
index ecd805f..78ad9e8 100644
--- a/build/config/operation.cxx
+++ b/build/config/operation.cxx
@@ -8,8 +8,9 @@
 
 #include <butl/filesystem>
 
-#include <build/scope>
 #include <build/file>
+#include <build/scope>
+#include <build/target>
 #include <build/context>
 #include <build/diagnostics>
 
diff --git a/build/config/utility b/build/config/utility
index 8ab6afe..e1d81a7 100644
--- a/build/config/utility
+++ b/build/config/utility
@@ -31,9 +31,9 @@ namespace build
     required (scope& root, const char* name, const char* default_value);
 
     // Set, if necessary, an optional config.* variable. In particular,
-    // an unspecified variable is set to NULL which is used to to
-    // distinguish between the "configured as unspecified" and "not
-    // yet configured" cases.
+    // an unspecified variable is set to NULL which is used to distinguish
+    // between the "configured as unspecified" and "not yet configured"
+    // cases.
     //
     // Return the pointer to the value, which can be NULL.
     //
diff --git a/build/context b/build/context
index 44948ec..a52232a 100644
--- a/build/context
+++ b/build/context
@@ -28,7 +28,6 @@ namespace build
   extern const operation_info* current_oif;
 
   extern execution_mode current_mode;
-  extern const target_rule_map* current_rules;
 
   // Reset the dependency state. In particular, this removes all the
   // targets, scopes, and variable names.
diff --git a/build/context.cxx b/build/context.cxx
index 22b6f53..d62be61 100644
--- a/build/context.cxx
+++ b/build/context.cxx
@@ -9,6 +9,8 @@
 #include <system_error>
 
 #include <build/scope>
+#include <build/target>
+#include <build/rule>
 #include <build/diagnostics>
 
 using namespace std;
@@ -22,7 +24,12 @@ namespace build
   const meta_operation_info* current_mif;
   const operation_info* current_oif;
   execution_mode current_mode;
-  const target_rule_map* current_rules;
+
+  // Builtin rules.
+  //
+  static dir_rule dir_;
+  static fsdir_rule fsdir_;
+  static file_rule file_;
 
   void
   reset ()
@@ -43,6 +50,35 @@ namespace build
 
     global_scope->assign ("work") = work;
     global_scope->assign ("home") = home;
+
+    // Register builtin target types.
+    //
+    {
+      target_type_map& tts (global_scope->target_types);
+
+      tts.insert<file>  ();
+      tts.insert<dir>   ();
+      tts.insert<fsdir> ();
+    }
+
+    // Register builtin rules.
+    //
+    {
+      rule_map& rs (global_scope->rules);
+
+      rs.insert<dir> (default_id, "dir", dir_);
+      rs.insert<dir> (update_id, "dir", dir_);
+      rs.insert<dir> (clean_id, "dir", dir_);
+
+      rs.insert<fsdir> (default_id, "fsdir", fsdir_);
+      rs.insert<fsdir> (update_id, "fsdir", fsdir_);
+      rs.insert<fsdir> (clean_id, "fsdir", fsdir_);
+
+      rs.insert<file> (default_id, "file", file_);
+      rs.insert<file> (update_id, "file", file_);
+      rs.insert<file> (clean_id, "file", file_);
+    }
+
   }
 
   fs_status<mkdir_status>
diff --git a/build/cxx/module b/build/cxx/module
index 2d50f59..dcadcdd 100644
--- a/build/cxx/module
+++ b/build/cxx/module
@@ -12,8 +12,8 @@ namespace build
 {
   namespace cxx
   {
-    void
-    init (scope&, scope&, const location&);
+    extern "C" void
+    cxx_init (scope&, scope&, const location&, std::unique_ptr<module>&, bool);
   }
 }
 
diff --git a/build/cxx/module.cxx b/build/cxx/module.cxx
index 7e6a211..ce7c968 100644
--- a/build/cxx/module.cxx
+++ b/build/cxx/module.cxx
@@ -10,10 +10,13 @@
 #include <build/scope>
 #include <build/diagnostics>
 
-#include <build/bin/module>
-
 #include <build/config/utility>
 
+#include <build/bin/target>
+
+#include <build/cxx/rule>
+#include <build/cxx/target>
+
 using namespace std;
 using namespace butl;
 
@@ -21,33 +24,73 @@ namespace build
 {
   namespace cxx
   {
-    void
-    init (scope& root, scope& base, const location& l)
+    compile compile_;
+    link link_;
+
+    extern "C" void
+    cxx_init (scope& root,
+              scope& base,
+              const location& l,
+              std::unique_ptr<module>&,
+              bool first)
     {
-      //@@ TODO: avoid multiple inits (generally, for modules).
-      //
-
       tracer trace ("cxx::init");
+      level4 ([&]{trace << "for " << base.path ();});
 
-      //@@ Should it be this way?
+      // Initialize the bin module. Only do this if it hasn't already
+      // been loaded so that we don't overwrite user's bin.* settings.
       //
-      if (&root != &base)
-        fail (l) << "cxx module must be initialized in project root scope";
+      if (base.find_target_type ("obj") == nullptr)
+        load_module ("bin", root, base, l);
 
-      // Initialize the bin module.
+      // Register target types.
       //
-      bin::init (root, base, l);
+      {
+        auto& tts (base.target_types);
+
+        tts.insert<h> ();
+        tts.insert<c> ();
 
-      //@@ TODO: need to register target types, rules here instead of main().
+        tts.insert<cxx> ();
+        tts.insert<hxx> ();
+        tts.insert<ixx> ();
+        tts.insert<txx> ();
+      }
 
-      const dir_path& out_root (root.path ());
-      level4 ([&]{trace << "for " << out_root;});
+      // Register rules.
+      //
+      {
+        using namespace bin;
+
+        auto& rs (base.rules);
+
+        rs.insert<obja> (default_id, "cxx.compile", compile_);
+        rs.insert<obja> (update_id, "cxx.compile", compile_);
+        rs.insert<obja> (clean_id, "cxx.compile", compile_);
+
+        rs.insert<objso> (default_id, "cxx.compile", compile_);
+        rs.insert<objso> (update_id, "cxx.compile", compile_);
+        rs.insert<objso> (clean_id, "cxx.compile", compile_);
+
+        rs.insert<exe> (default_id, "cxx.link", link_);
+        rs.insert<exe> (update_id, "cxx.link", link_);
+        rs.insert<exe> (clean_id, "cxx.link", link_);
+
+        rs.insert<liba> (default_id, "cxx.link", link_);
+        rs.insert<liba> (update_id, "cxx.link", link_);
+        rs.insert<liba> (clean_id, "cxx.link", link_);
+
+        rs.insert<libso> (default_id, "cxx.link", link_);
+        rs.insert<libso> (update_id, "cxx.link", link_);
+        rs.insert<libso> (clean_id, "cxx.link", link_);
+      }
 
       // Configure.
       //
 
       // config.cxx
       //
+      if (first)
       {
         auto r (config::required (root, "config.cxx", "g++"));
 
@@ -98,17 +141,27 @@ namespace build
       // These are optional. We also merge them into the corresponding
       // cxx.* variables.
       //
+      // The merging part gets a bit tricky if this module has already
+      // been loaded in one of the outer scopes. By doing the straight
+      // append we would just be repeating the same options over and
+      // over. So what we are going to do is only append to a value if
+      // it came from this scope. Then the usage for merging becomes:
+      //
+      // cxx.coptions = <overridable options> # Note: '='.
+      // using cxx
+      // cxx.coptions += <overriding options> # Note: '+='.
+      //
       if (auto* v = config::optional<list_value> (root, "config.cxx.poptions"))
-        root.append ("cxx.poptions") += *v;
+        base.assign ("cxx.poptions") += *v;
 
       if (auto* v = config::optional<list_value> (root, "config.cxx.coptions"))
-        root.append ("cxx.coptions") += *v;
+        base.assign ("cxx.coptions") += *v;
 
       if (auto* v = config::optional<list_value> (root, "config.cxx.loptions"))
-        root.append ("cxx.loptions") += *v;
+        base.assign ("cxx.loptions") += *v;
 
       if (auto* v = config::optional<list_value> (root, "config.cxx.libs"))
-        root.append ("cxx.libs") += *v;
+        base.assign ("cxx.libs") += *v;
     }
   }
 }
diff --git a/build/module b/build/module
index 54a202c..43ab1e0 100644
--- a/build/module
+++ b/build/module
@@ -5,18 +5,47 @@
 #ifndef BUILD_MODULE
 #define BUILD_MODULE
 
+#include <map>
 #include <string>
-#include <unordered_map>
+#include <memory> // unique_ptr
 
 namespace build
 {
   class scope;
   class location;
 
-  using module_init_function = void (scope& root, scope& base, const location&);
-  using module_map = std::unordered_map<std::string, module_init_function*>;
+  class module
+  {
+  public:
+    virtual
+    ~module () = default;
+  };
 
-  extern module_map modules;
+  extern "C"
+  using module_init_function =
+    void (scope& root,
+          scope& base,
+          const location&,
+          std::unique_ptr<module>&,
+          bool first); // First time for this project.
+
+  using loaded_module_map =
+    std::map<std::string,
+             std::pair<module_init_function*, std::unique_ptr<module>>>;
+
+  // Load the specified module. Used by the parser but also by some
+  // modules to load prerequisite modules.
+  //
+  void
+  load_module (const std::string& name,
+               scope& root,
+               scope& base,
+               const location&);
+
+  // Builtin modules.
+  //
+  using available_module_map = std::map<std::string, module_init_function*>;
+  extern available_module_map builtin_modules;
 }
 
 #endif // BUILD_MODULE
diff --git a/build/module.cxx b/build/module.cxx
index 6b410e6..0f2b1b2 100644
--- a/build/module.cxx
+++ b/build/module.cxx
@@ -4,9 +4,39 @@
 
 #include <build/module>
 
+#include <utility> // make_pair()
+
+#include <build/scope>
+#include <build/diagnostics>
+
 using namespace std;
 
 namespace build
 {
-  module_map modules;
+  available_module_map builtin_modules;
+
+  void
+  load_module (const string& name, scope& root, scope& base, const location& l)
+  {
+    // First see if this modules has already been loaded for this
+    // project.
+    //
+    loaded_module_map& lm (root.modules);
+    auto i (lm.find (name));
+    bool f (i == lm.end ());
+
+    if (f)
+    {
+      // Otherwise search for this module.
+      //
+      auto j (builtin_modules.find (name));
+
+      if (j == builtin_modules.end ())
+        fail (l) << "unknown module " << name;
+
+      i = lm.emplace (name, make_pair (j->second, nullptr)).first;
+    }
+
+    i->second.first (root, base, l, i->second.second, f);
+  }
 }
diff --git a/build/parser.cxx b/build/parser.cxx
index c8bc241..59e3783 100644
--- a/build/parser.cxx
+++ b/build/parser.cxx
@@ -261,7 +261,7 @@ namespace build
           auto enter_target = [this, &nloc, &trace] (name&& tn) -> target&
           {
             const string* e;
-            const target_type* ti (target_types.find (tn, e));
+            const target_type* ti (scope_->find_target_type (tn, e));
 
             if (ti == nullptr)
               fail (nloc) << "unknown target type " << tn.type;
@@ -335,7 +335,7 @@ namespace build
             for (auto& pn: pns)
             {
               const string* e;
-              const target_type* ti (target_types.find (pn, e));
+              const target_type* ti (scope_->find_target_type (pn, e));
 
               if (ti == nullptr)
                 fail (ploc) << "unknown target type " << pn.type;
@@ -720,16 +720,10 @@ namespace build
     {
       // For now it should be a simple name.
       //
-      if (!n.type.empty () || !n.dir.empty ())
+      if (!n.simple ())
         fail (l) << "module name expected instead of " << n;
 
-      const string& name (n.value);
-      auto i (modules.find (name));
-
-      if (i == modules.end ())
-        fail (l) << "unknown module " << name;
-
-      i->second (*root_, *scope_, l);
+      load_module (n.value, *root_, *scope_, l);
     }
 
     if (tt == type::newline)
diff --git a/build/rule b/build/rule
index eda6ed3..fbcf06b 100644
--- a/build/rule
+++ b/build/rule
@@ -7,11 +7,6 @@
 
 #include <string>
 #include <cstddef>        // nullptr_t
-#include <typeindex>
-#include <functional>     // reference_wrapper
-#include <unordered_map>
-
-#include <butl/prefix-map>
 
 #include <build/types>
 #include <build/target>
@@ -56,14 +51,6 @@ namespace build
     apply (action, target&, const match_result&) const = 0;
   };
 
-  using target_rule_map = std::unordered_map<
-    std::type_index,
-    butl::prefix_map<std::string, std::reference_wrapper<rule>, '.'>>;
-
-  using operation_rule_map = std::unordered_map<operation_id, target_rule_map>;
-
-  extern operation_rule_map rules;
-
   // Fallback rule that on update verifies that the file exists and is
   // not older than any of its prerequisites.
   //
diff --git a/build/rule-map b/build/rule-map
new file mode 100644
index 0000000..883800b
--- /dev/null
+++ b/build/rule-map
@@ -0,0 +1,46 @@
+// file      : build/rule-map -*- C++ -*-
+// copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef BUILD_RULE_MAP
+#define BUILD_RULE_MAP
+
+#include <map>
+#include <vector>
+#include <string>
+#include <typeindex>
+#include <functional>     // reference_wrapper
+
+#include <butl/prefix-map>
+
+#include <build/types>
+#include <build/operation>
+
+namespace build
+{
+  class rule;
+
+  using target_type_rule_map = std::map<
+    std::type_index,              // Target type.
+    butl::prefix_map<std::string, // Rule hint.
+                     std::reference_wrapper<rule>, '.'>>;
+
+  // This is an "indexed map" with (operation_id - 1) being the
+  // index.
+  //
+  class rule_map: public std::vector<target_type_rule_map>
+  {
+  public:
+    template <typename T>
+    void
+    insert (operation_id oid, const char* hint, rule& r)
+    {
+      if (oid > size ())
+        resize (oid < 3 ? 3 : oid); // 3 is the number of builtin operations.
+
+      (*this)[oid - 1][typeid (T)].emplace (hint, r);
+    }
+  };
+}
+
+#endif // BUILD_RULE_MAP
diff --git a/build/rule.cxx b/build/rule.cxx
index a8c77a8..eadbecb 100644
--- a/build/rule.cxx
+++ b/build/rule.cxx
@@ -10,6 +10,7 @@
 #include <butl/filesystem>
 
 #include <build/scope>
+#include <build/target>
 #include <build/algorithm>
 #include <build/diagnostics>
 #include <build/context>
@@ -19,8 +20,6 @@ using namespace butl;
 
 namespace build
 {
-  operation_rule_map rules;
-
   // file_rule
   //
   // Note that this rule is special. It is the last, fallback rule. If
diff --git a/build/scope b/build/scope
index 5266370..d1cd941 100644
--- a/build/scope
+++ b/build/scope
@@ -12,8 +12,11 @@
 #include <butl/path-map>
 
 #include <build/types>
+#include <build/module>
 #include <build/variable>
 #include <build/prerequisite>
+#include <build/target-type>
+#include <build/rule-map>
 #include <build/operation>
 
 namespace build
@@ -60,10 +63,11 @@ namespace build
       return operator[] (variable_pool.find (name));
     }
 
-    // Return a value_proxy suitable for assignment. If the variable
-    // does not exist in this scope's map, then a new one with the
-    // NULL value is added and returned. Otherwise the existing value
-    // if returned.
+    // Return a value_proxy suitable for assignment (or append if you
+    // only want to append to the value from this scope). If the variable
+    // does not exist in this scope's map, then a new one with the NULL
+    // value is added and returned. Otherwise the existing value is
+    // returned.
     //
     value_proxy
     assign (const variable& var)
@@ -92,6 +96,8 @@ namespace build
       return append (variable_pool.find (name));
     }
 
+    // Prerequisite cache.
+    //
   public:
     prerequisite_set prerequisites;
 
@@ -109,6 +115,33 @@ namespace build
     //
     std::unordered_set<path_type> buildfiles;
 
+    // Target types.
+    //
+  public:
+    target_type_map target_types;
+
+    const target_type*
+    find_target_type (const char*, const scope** = nullptr) const;
+
+    // Given a name, figure out its type, taking into account extensions,
+    // special names (e.g., '.' and '..'), or anything else that might be
+    // relevant. Also process the name (in place) by extracting the
+    // extension, adjusting dir/value, etc., (note that the dir is not
+    // necessarily normalized). Return NULL if not found.
+    //
+    const target_type*
+    find_target_type (name&, const std::string*& ext) const;
+
+    // Rules.
+    //
+  public:
+    rule_map rules;
+
+    // Modules.
+    //
+  public:
+    loaded_module_map modules; // Only on root scope.
+
   private:
     friend class scope_map;
     friend class temp_scope;
diff --git a/build/scope.cxx b/build/scope.cxx
index 5bd2b62..4645979 100644
--- a/build/scope.cxx
+++ b/build/scope.cxx
@@ -4,6 +4,8 @@
 
 #include <build/scope>
 
+#include <build/target>
+
 using namespace std;
 
 namespace build
@@ -40,6 +42,104 @@ namespace build
     return r;
   }
 
+  const target_type* scope::
+  find_target_type (const char* tt, const scope** rs) const
+  {
+    // Search scopes outwards, stopping at the project root.
+    //
+    for (const scope* s (this);
+         s != nullptr;
+         s = s->root () ? global_scope : s->parent_scope ())
+    {
+      if (s->target_types.empty ())
+        continue;
+
+      auto i (s->target_types.find (tt));
+
+      if (i != s->target_types.end ())
+      {
+        if (rs != nullptr)
+          *rs = s;
+
+        return &i->second.get ();
+      }
+    }
+
+    return nullptr;
+  }
+
+  const target_type* scope::
+  find_target_type (name& n, const string*& ext) const
+  {
+    ext = nullptr;
+
+    string& v (n.value);
+
+    // First determine the target type.
+    //
+    const char* tt;
+    if (n.type.empty ())
+    {
+      // Empty name or '.' and '..' signify a directory.
+      //
+      if (v.empty () || v == "." || v == "..")
+        tt = "dir";
+      else
+        //@@ TODO: derive type from extension.
+        //
+        tt = "file";
+    }
+    else
+      tt = n.type.c_str ();
+
+    const target_type* r (find_target_type (tt));
+
+    if (r == nullptr)
+      return r;
+
+    // Directories require special name processing. If we find that more
+    // targets deviate, then we should make this target-type-specific.
+    //
+    if (r->is_a<dir> () || r->is_a<fsdir> ())
+    {
+      // The canonical representation of a directory name is with empty
+      // value.
+      //
+      if (!v.empty ())
+      {
+        n.dir /= dir_path (v); // Move name value to dir.
+        v.clear ();
+      }
+    }
+    else
+    {
+      // Split the path into its directory part (if any) the name part,
+      // and the extension (if any). We cannot assume the name part is
+      // a valid filesystem name so we will have to do the splitting
+      // manually.
+      //
+      path::size_type i (path::traits::rfind_separator (v));
+
+      if (i != string::npos)
+      {
+        n.dir /= dir_path (v, i != 0 ? i : 1); // Special case: "/".
+        v = string (v, i + 1, string::npos);
+      }
+
+      // Extract the extension.
+      //
+      string::size_type j (path::traits::find_extension (v));
+
+      if (j != string::npos)
+      {
+        ext = &extension_pool.find (v.c_str () + j + 1);
+        v.resize (j);
+      }
+    }
+
+    return r;
+  }
+
   // scope_map
   //
   scope_map scopes;
diff --git a/build/target b/build/target
index 4131338..954604c 100644
--- a/build/target
+++ b/build/target
@@ -10,19 +10,20 @@
 #include <vector>
 #include <memory>      // unique_ptr
 #include <cstddef>     // size_t
-#include <functional>  // function, reference_wrapper
+#include <functional>  // reference_wrapper
 #include <ostream>
 #include <cassert>
 #include <utility>     // move(), forward(), declval()
 #include <iterator>
 #include <type_traits>
 
-#include <butl/utility>     // compare_c_string, reverse_iterate()
+#include <butl/utility>     // reverse_iterate()
 #include <butl/multi-index> // map_iterator_adapter
 
 #include <build/types>
 #include <build/variable>
 #include <build/operation>
+#include <build/target-type>
 #include <build/target-key>
 #include <build/prerequisite>
 
@@ -756,31 +757,6 @@ namespace build
 
   extern target_set targets;
 
-  using target_type_map_base = std::map<
-    const char*,
-    std::reference_wrapper<const target_type>,
-    butl::compare_c_string>;
-
-  class target_type_map: public target_type_map_base
-  {
-  public:
-    void
-    insert (const target_type& tt) {emplace (tt.name, tt);}
-
-    using target_type_map_base::find;
-
-    // Given a name, figure out its type, taking into account extensions,
-    // special names (e.g., '.' and '..'), or anything else that might be
-    // relevant. Also process the name (in place) by extracting the
-    // extension, adjusting dir/value, etc (note that the dir is not
-    // necessarily normalized). Return NULL if not found.
-    //
-    const target_type*
-    find (name&, const std::string*& ext) const;
-  };
-
-  extern target_type_map target_types;
-
   // Modification time-based target.
   //
   class mtime_target: public target
diff --git a/build/target-key b/build/target-key
index 54813b0..37fa6ab 100644
--- a/build/target-key
+++ b/build/target-key
@@ -5,45 +5,19 @@
 #ifndef BUILD_TARGET_KEY
 #define BUILD_TARGET_KEY
 
+#include <map>
 #include <string>
-#include <typeindex>
 #include <ostream>
+#include <typeindex>
+#include <functional>  // reference_wrapper
+
+#include <butl/utility> // compare_c_string
 
 #include <build/types>
+#include <build/target-type>
 
 namespace build
 {
-  class scope;
-  class target;
-  class target_key;
-  class prerequisite_key;
-
-  // Target type.
-  //
-  struct target_type
-  {
-    std::type_index id;
-    const char* name;
-    const target_type* base;
-    target* (*const factory) (dir_path, std::string, const std::string*);
-    const std::string& (*const extension) (const target_key&, scope&);
-    target* (*const search) (const prerequisite_key&);
-    bool see_through; // A group with the default "see through" semantics.
-
-    bool
-    is_a (const std::type_index&) const; // Defined in target.cxx
-
-    template <typename T>
-    bool
-    is_a () const {return is_a (typeid (T));}
-  };
-
-  inline std::ostream&
-  operator<< (std::ostream& os, const target_type& tt)
-  {
-    return os << tt.name;
-  }
-
   // Light-weight (by being shallow-pointing) target key.
   //
   class target_key
diff --git a/build/target-type b/build/target-type
new file mode 100644
index 0000000..d5e7971
--- /dev/null
+++ b/build/target-type
@@ -0,0 +1,70 @@
+// file      : build/target-type -*- C++ -*-
+// copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef BUILD_TARGET_TYPE
+#define BUILD_TARGET_TYPE
+
+#include <map>
+#include <string>
+#include <ostream>
+#include <typeindex>
+#include <functional>  // reference_wrapper
+
+#include <butl/utility> // compare_c_string
+
+#include <build/types>
+
+namespace build
+{
+  class scope;
+  class target;
+  class target_key;
+  class prerequisite_key;
+
+  // Target type.
+  //
+  struct target_type
+  {
+    std::type_index id;
+    const char* name;
+    const target_type* base;
+    target* (*const factory) (dir_path, std::string, const std::string*);
+    const std::string& (*const extension) (const target_key&, scope&);
+    target* (*const search) (const prerequisite_key&);
+    bool see_through; // A group with the default "see through" semantics.
+
+    bool
+    is_a (const std::type_index&) const; // Defined in target.cxx
+
+    template <typename T>
+    bool
+    is_a () const {return is_a (typeid (T));}
+  };
+
+  inline std::ostream&
+  operator<< (std::ostream& os, const target_type& tt)
+  {
+    return os << tt.name;
+  }
+
+  // Target type map.
+  //
+  using target_type_map_base = std::map<
+    const char*,
+    std::reference_wrapper<const target_type>,
+    butl::compare_c_string>;
+
+  class target_type_map: public target_type_map_base
+  {
+  public:
+    void
+    insert (const target_type& tt) {emplace (tt.name, tt);}
+
+    template <typename T>
+    void
+    insert () {insert (T::static_type);}
+  };
+}
+
+#endif // BUILD_TARGET_TYPE
diff --git a/build/target.cxx b/build/target.cxx
index f692a5e..63bb2fe 100644
--- a/build/target.cxx
+++ b/build/target.cxx
@@ -197,83 +197,6 @@ namespace build
     return os;
   }
 
-  //
-  //
-  target_type_map target_types;
-
-  const target_type* target_type_map::
-  find (name& n, const string*& ext) const
-  {
-    ext = nullptr;
-
-    string& v (n.value);
-
-    // First determine the target type.
-    //
-    const char* tt;
-    if (n.type.empty ())
-    {
-      // Empty name or '.' and '..' signify a directory.
-      //
-      if (v.empty () || v == "." || v == "..")
-        tt = "dir";
-      else
-        //@@ TODO: derive type from extension.
-        //
-        tt = "file";
-    }
-    else
-      tt = n.type.c_str ();
-
-    auto i (find (tt));
-    if (i == end ())
-      return nullptr;
-
-    const target_type& ti (i->second);
-
-    // Directories require special name processing. If we find that more
-    // targets deviate, then we should make this target-type-specific.
-    //
-    if (ti.id == dir::static_type.id || ti.id == fsdir::static_type.id)
-    {
-      // The canonical representation of a directory name is with empty
-      // value.
-      //
-      if (!v.empty ())
-      {
-        n.dir /= dir_path (v); // Move name value to dir.
-        v.clear ();
-      }
-    }
-    else
-    {
-      // Split the path into its directory part (if any) the name part,
-      // and the extension (if any). We cannot assume the name part is
-      // a valid filesystem name so we will have to do the splitting
-      // manually.
-      //
-      path::size_type i (path::traits::rfind_separator (v));
-
-      if (i != string::npos)
-      {
-        n.dir /= dir_path (v, i != 0 ? i : 1); // Special case: "/".
-        v = string (v, i + 1, string::npos);
-      }
-
-      // Extract the extension.
-      //
-      string::size_type j (path::traits::find_extension (v));
-
-      if (j != string::npos)
-      {
-        ext = &extension_pool.find (v.c_str () + j + 1);
-        v.resize (j);
-      }
-    }
-
-    return &ti;
-  }
-
   // path_target
   //
   void path_target::