Redesign obj to exe/lib mapping

Specifically:

* objso{} and libso{} target types have been renamed to objs{} and libs{}

* obje{} has been added (so now we have obje{}, obja{}, and objs{})

* obje{} is now used for building exe{}

* object file extensions have been changed to use "hierarchical extensions"
  that reflect the extension of the corresponding exe/lib target (instead of
  the -so suffix we used), specifically:

  obje{}: foo.o, (UNIX), foo.exe.o (MinGW), foo.exe.obj (Windows)
  obja{}: foo.a.o (UNIX, MinGW), foo.lib.obj (Windows)
  objs{}: foo.so.o (UNIX), foo.dylib.o (Darwin), foo.dll.o (MinGW),
          foo.dll.obj (Windows)

9 files changed, 320 insertions, 188 deletions

diff --git a/build2/cxx/common b/build2/cxx/common
new file mode 100644
index 0000000..77f1149
--- /dev/null
+++ b/build2/cxx/common
@@ -0,0 +1,60 @@
+// file      : build2/cxx/common -*- C++ -*-
+// copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef BUILD2_CXX_COMMON
+#define BUILD2_CXX_COMMON
+
+#include <build2/types>
+#include <build2/utility>
+
+#include <build2/bin/target>
+
+namespace build2
+{
+  namespace cxx
+  {
+    // Compile/link output type (executable, static, or shared).
+    //
+    enum class otype {e, a, s};
+
+    inline otype
+    compile_type (target& t)
+    {
+      return
+        t.is_a<bin::obje> () ? otype::e :
+        t.is_a<bin::obja> () ? otype::a :
+        otype::s;
+    }
+
+    inline otype
+    link_type (target& t)
+    {
+      return
+        t.is_a<bin::exe> ()  ? otype::e :
+        t.is_a<bin::liba> () ? otype::a :
+        otype::s;
+    }
+
+    // Library link order.
+    //
+    enum class lorder {a, s, a_s, s_a};
+
+    // The reason we pass scope and not the target is because this function is
+    // called not only for exe/lib but also for obj as part of the library
+    // meta-information protocol implementation. Normally the bin.*.lib values
+    // will be project-wide. With this scheme they can be customized on the
+    // per-directory basis but not per-target which means all exe/lib in the
+    // same directory have to have the same link order.
+    //
+    lorder
+    link_order (scope& base, otype);
+
+    // Given the link order return the library member (liba or libs) to link.
+    //
+    target&
+    link_member (bin::lib&, lorder);
+  }
+}
+
+#endif // BUILD2_CXX_COMMON
diff --git a/build2/cxx/common.cxx b/build2/cxx/common.cxx
new file mode 100644
index 0000000..0b66eb5
--- /dev/null
+++ b/build2/cxx/common.cxx
@@ -0,0 +1,70 @@
+// file      : build2/cxx/common.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <build2/cxx/common>
+
+#include <build2/variable>
+#include <build2/algorithm>
+
+using namespace std;
+
+namespace build2
+{
+  namespace cxx
+  {
+    using namespace bin;
+
+    lorder
+    link_order (scope& bs, otype ot)
+    {
+      const char* var;
+
+      switch (ot)
+      {
+      case otype::e: var = "bin.exe.lib";  break;
+      case otype::a: var = "bin.liba.lib"; break;
+      case otype::s: var = "bin.libs.lib"; break;
+      }
+
+      const auto& v (cast<strings> (bs[var]));
+      return v[0] == "shared"
+        ? v.size () > 1 && v[1] == "static" ? lorder::s_a : lorder::s
+        : v.size () > 1 && v[1] == "shared" ? lorder::a_s : lorder::a;
+    }
+
+    target&
+    link_member (bin::lib& l, lorder lo)
+    {
+      bool ls (true);
+      const string& at (cast<string> (l["bin.lib"])); // Available members.
+
+      switch (lo)
+      {
+      case lorder::a:
+      case lorder::a_s:
+        ls = false; // Fall through.
+      case lorder::s:
+      case lorder::s_a:
+        {
+          if (ls ? at == "static" : at == "shared")
+          {
+            if (lo == lorder::a_s || lo == lorder::s_a)
+              ls = !ls;
+            else
+              fail << (ls ? "shared" : "static") << " variant of " << l
+                   << " is not available";
+          }
+        }
+      }
+
+      target* r (ls ? static_cast<target*> (l.s) : l.a);
+
+      if (r == nullptr)
+        r = &search (ls ? libs::static_type : liba::static_type,
+                     prerequisite_key {nullptr, l.key (), nullptr});
+
+      return *r;
+    }
+  }
+}
diff --git a/build2/cxx/compile.cxx b/build2/cxx/compile.cxx
index 504df7f..645e818 100644
--- a/build2/cxx/compile.cxx
+++ b/build2/cxx/compile.cxx
@@ -21,6 +21,7 @@
 #include <build2/cxx/target>
 
 #include <build2/cxx/link>
+#include <build2/cxx/common>
 #include <build2/cxx/utility>
 
 
@@ -69,15 +70,57 @@ namespace build2
       path_target& t (static_cast<path_target&> (xt));
 
       scope& rs (t.root_scope ());
+
       const string& cid (cast<string> (rs["cxx.id"]));
+      const string& tsys (cast<string> (rs["cxx.target.system"]));
       const string& tclass (cast<string> (rs["cxx.target.class"]));
 
+      otype ct (compile_type (t));
+
       // Derive file name from target name.
       //
       if (t.path ().empty ())
       {
-        const char* ext (cid == "msvc" ? "obj" : "o");
-        t.derive_path (ext, nullptr, (t.is_a<objso> () ? "-so" : nullptr));
+        const char* e (nullptr);
+
+        if (tsys == "win32-msvc")
+        {
+          switch (ct)
+          {
+          case otype::e: e = "exe.obj"; break;
+          case otype::a: e = "lib.obj"; break;
+          case otype::s: e = "dll.obj"; break;
+          }
+        }
+        else if (tsys == "mingw32")
+        {
+          switch (ct)
+          {
+          case otype::e: e = "exe.o"; break;
+          case otype::a: e = "a.o";   break;
+          case otype::s: e = "dll.o"; break;
+          }
+        }
+        else if (tsys == "darwin")
+        {
+          switch (ct)
+          {
+          case otype::e: e = "o";       break;
+          case otype::a: e = "a.o";     break;
+          case otype::s: e = "dylib.o"; break;
+          }
+        }
+        else
+        {
+          switch (ct)
+          {
+          case otype::e: e = "o"; break;
+          case otype::a: e = "a.o"; break;
+          case otype::s: e = "so.o"; break;
+          }
+        }
+
+        t.derive_path (e);
       }
 
       // Inject dependency on the output directory.
@@ -102,7 +145,7 @@ namespace build2
         // meta-information protocol". See also append_lib_options()
         // above.
         //
-        if (p.is_a<lib> () || p.is_a<liba> () || p.is_a<libso> ())
+        if (p.is_a<lib> () || p.is_a<liba> () || p.is_a<libs> ())
         {
           if (a.operation () == update_id)
           {
@@ -184,7 +227,7 @@ namespace build2
         {
           target& pt (*p.target); // Already searched and matched.
 
-          if (pt.is_a<lib> () || pt.is_a<liba> () || pt.is_a<libso> ())
+          if (pt.is_a<lib> () || pt.is_a<liba> () || pt.is_a<libs> ())
             hash_lib_options (cs, pt, "cxx.export.poptions");
         }
 
@@ -192,7 +235,7 @@ namespace build2
         hash_options (cs, t, "cxx.coptions");
         hash_std (cs, rs, cid, t);
 
-        if (t.is_a<objso> ())
+        if (ct == otype::s)
         {
           // On Darwin, Win32 -fPIC is the default.
           //
@@ -369,7 +412,7 @@ namespace build2
         if (t == nullptr)
           continue;
 
-        if (t->is_a<lib> () || t->is_a<liba> () || t->is_a<libso> ())
+        if (t->is_a<lib> () || t->is_a<liba> () || t->is_a<libs> ())
           append_lib_prefixes (m, *t);
       }
 
@@ -389,7 +432,7 @@ namespace build2
       {
         target& pt (*p.target); // Already searched and matched.
 
-        if (pt.is_a<lib> () || pt.is_a<liba> () || pt.is_a<libso> ())
+        if (pt.is_a<lib> () || pt.is_a<liba> () || pt.is_a<libs> ())
           append_lib_prefixes (m, pt);
       }
 
@@ -617,7 +660,7 @@ namespace build2
         {
           target& pt (*p.target); // Already searched and matched.
 
-          if (pt.is_a<lib> () || pt.is_a<liba> () || pt.is_a<libso> ())
+          if (pt.is_a<lib> () || pt.is_a<liba> () || pt.is_a<libs> ())
             append_lib_options (args, pt, "cxx.export.poptions");
         }
 
@@ -628,7 +671,7 @@ namespace build2
         append_options (args, t, "cxx.coptions");
         append_std (args, rs, cid, t, cxx_std);
 
-        if (t.is_a<objso> ())
+        if (t.is_a<objs> ())
         {
           // On Darwin, Win32 -fPIC is the default.
           //
@@ -1181,19 +1224,22 @@ namespace build2
       if (s == nullptr)
         return target_state::unchanged;
 
-      // Translate paths to relative (to working directory) ones. This
-      // results in easier to read diagnostics.
-      //
-      path relo (relative (t.path ()));
-      path rels (relative (s->path ()));
-
       scope& rs (t.root_scope ());
+
       const path& cxx (cast<path> (rs["config.cxx"]));
       const string& cid (cast<string> (rs["cxx.id"]));
       const string& tclass (cast<string> (rs["cxx.target.class"]));
 
+      otype ct (compile_type (t));
+
       cstrings args {cxx.string ().c_str ()};
 
+      // Translate paths to relative (to working directory) ones. This
+      // results in easier to read diagnostics.
+      //
+      path relo (relative (t.path ()));
+      path rels (relative (s->path ()));
+
       // Add cxx.export.poptions from prerequisite libraries. Note that
       // here we don't need to see group members (see apply()).
       //
@@ -1201,7 +1247,7 @@ namespace build2
       {
         target& pt (*p.target); // Already searched and matched.
 
-        if (pt.is_a<lib> () || pt.is_a<liba> () || pt.is_a<libso> ())
+        if (pt.is_a<lib> () || pt.is_a<liba> () || pt.is_a<libs> ())
           append_lib_options (args, pt, "cxx.export.poptions");
       }
 
@@ -1268,7 +1314,7 @@ namespace build2
       }
       else
       {
-        if (t.is_a<objso> ())
+        if (ct == otype::s)
         {
           // On Darwin, Win32 -fPIC is the default.
           //
diff --git a/build2/cxx/install.cxx b/build2/cxx/install.cxx
index f6f502a..e07d115 100644
--- a/build2/cxx/install.cxx
+++ b/build2/cxx/install.cxx
@@ -6,8 +6,9 @@
 
 #include <build2/bin/target>
 
-#include <build2/cxx/target>
 #include <build2/cxx/link>
+#include <build2/cxx/common>
+#include <build2/cxx/target>
 
 using namespace std;
 
@@ -31,17 +32,20 @@ namespace build2
       // If this is a shared library prerequisite, install it as long as it
       // is in the same amalgamation as we are.
       //
-      if ((t.is_a<exe> () || t.is_a<libso> ()) &&
-          (p.is_a<lib> () || p.is_a<libso> ()))
+      // @@ Shouldn't we also install a static library prerequisite of a
+      //    static library?
+      //
+      if ((t.is_a<exe> () || t.is_a<libs> ()) &&
+          (p.is_a<lib> () || p.is_a<libs> ()))
       {
         target* pt (&p.search ());
 
         // If this is the lib{} group, pick a member which we would link.
         //
         if (lib* l = pt->is_a<lib> ())
-          pt = &link::link_member (*l, link::link_order (t));
+          pt = &link_member (*l, link_order (t.base_scope (), link_type (t)));
 
-        if (pt->is_a<libso> ()) // Can be liba{}.
+        if (pt->is_a<libs> ()) // Can be liba{}.
           return pt->in (t.weak_scope ()) ? pt : nullptr;
       }
 
diff --git a/build2/cxx/link b/build2/cxx/link
index ca45e17..4f00ea0 100644
--- a/build2/cxx/link
+++ b/build2/cxx/link
@@ -33,26 +33,6 @@ namespace build2
 
       static link instance;
 
-    public:
-      enum class type {e, a, so};
-      enum class order {a, so, a_so, so_a};
-
-      static type
-      link_type (target& t)
-      {
-        return t.is_a<bin::exe> ()
-          ? type::e
-          : (t.is_a<bin::liba> () ? type::a : type::so);
-      }
-
-      static order
-      link_order (target&);
-
-      // Determine the library member (liba or libso) to link.
-      //
-      static target&
-      link_member (bin::lib&, order);
-
     private:
       friend class compile;
 
diff --git a/build2/cxx/link.cxx b/build2/cxx/link.cxx
index 181c2b8..002cd42 100644
--- a/build2/cxx/link.cxx
+++ b/build2/cxx/link.cxx
@@ -19,6 +19,7 @@
 #include <build2/bin/target>
 #include <build2/cxx/target>
 
+#include <build2/cxx/common>
 #include <build2/cxx/utility>
 
 using namespace std;
@@ -30,58 +31,6 @@ namespace build2
   {
     using namespace bin;
 
-    link::order link::
-    link_order (target& t)
-    {
-      const char* var;
-
-      switch (link_type (t))
-      {
-      case type::e:  var = "bin.exe.lib";   break;
-      case type::a:  var = "bin.liba.lib";  break;
-      case type::so: var = "bin.libso.lib"; break;
-      }
-
-      const auto& v (cast<strings> (t[var]));
-      return v[0] == "shared"
-        ? v.size () > 1 && v[1] == "static" ? order::so_a : order::so
-        : v.size () > 1 && v[1] == "shared" ? order::a_so : order::a;
-    }
-
-    target& link::
-    link_member (bin::lib& l, order lo)
-    {
-      bool lso (true);
-      const string& at (cast<string> (l["bin.lib"])); // Available types.
-
-      switch (lo)
-      {
-      case order::a:
-      case order::a_so:
-        lso = false; // Fall through.
-      case order::so:
-      case order::so_a:
-        {
-          if (lso ? at == "static" : at == "shared")
-          {
-            if (lo == order::a_so || lo == order::so_a)
-              lso = !lso;
-            else
-              fail << (lso ? "shared" : "static") << " build of " << l
-                   << " is not available";
-          }
-        }
-      }
-
-      target* r (lso ? static_cast<target*> (l.so) : l.a);
-
-      if (r == nullptr)
-        r = &search (lso ? libso::static_type : liba::static_type,
-                     prerequisite_key {nullptr, l.key (), nullptr});
-
-      return *r;
-    }
-
     // Extract system library search paths from GCC or compatible (Clang,
     // Intel C++) using the -print-search-dirs option.
     //
@@ -261,7 +210,7 @@ namespace build2
       const string& tsys (cast<string> (rs["cxx.target.system"]));
 
       bool l (p.is_a<lib> ());
-      const string* ext (l ? nullptr : p.ext); // Only for liba/libso.
+      const string* ext (l ? nullptr : p.ext); // Only for liba/libs.
 
       // Then figure out what we need to search for.
       //
@@ -302,12 +251,12 @@ namespace build2
         }
       }
 
-      // libso
+      // libs
       //
       path sn;
       const string* se (nullptr);
 
-      if (l || p.is_a<libso> ())
+      if (l || p.is_a<libs> ())
       {
         const char* e ("");
 
@@ -358,7 +307,7 @@ namespace build2
         spc = extract_library_paths (p.scope);
 
       liba* a (nullptr);
-      libso* s (nullptr);
+      libs* s (nullptr);
 
       path f; // Reuse the buffer.
       const dir_path* pd;
@@ -390,7 +339,7 @@ namespace build2
           }
         }
 
-        // libso
+        // libs
         //
         if (!sn.empty ())
         {
@@ -403,7 +352,7 @@ namespace build2
             // Above we searched for the import library (.dll.a) but if it's
             // not found, then we also search for the .dll (unless the
             // extension was specified explicitly) since we can link to it
-            // directly. Note also that the resulting libso{} would end up
+            // directly. Note also that the resulting libs{} would end up
             // being the .dll.
             //
             if (mt == timestamp_nonexistent && ext == nullptr)
@@ -416,7 +365,7 @@ namespace build2
 
           if (mt != timestamp_nonexistent)
           {
-            s = &targets.insert<libso> (d, dir_path (), p.name, se, trace);
+            s = &targets.insert<libs> (d, dir_path (), p.name, se, trace);
 
             if (s->path ().empty ())
               s->path (move (f));
@@ -444,7 +393,7 @@ namespace build2
         // It should automatically link-up to the members we have found.
         //
         assert (l.a == a);
-        assert (l.so == s);
+        assert (l.s == s);
 
         // Set the bin.lib variable to indicate what's available.
         //
@@ -474,11 +423,11 @@ namespace build2
       //
       // - if there is no .o, are we going to check if the one derived
       //   from target exist or can be built? A: No.
-      //   What if there is a library. Probably ok if .a, not if .so.
+      //   What if there is a library. Probably ok if static, not if shared,
       //   (i.e., a utility library).
       //
 
-      type lt (link_type (t));
+      otype lt (link_type (t));
 
       // Scan prerequisites and see if we can work with what we've got.
       //
@@ -495,22 +444,34 @@ namespace build2
         {
           seen_c = seen_c || true;
         }
+        else if (p.is_a<obj> ())
+        {
+          seen_obj = seen_obj || true;
+        }
+        else if (p.is_a<obje> ())
+        {
+          if (lt != otype::e)
+            fail << "obje{} as prerequisite of " << t;
+
+          seen_obj = seen_obj || true;
+        }
         else if (p.is_a<obja> ())
         {
-          if (lt == type::so)
-            fail << "shared library " << t << " prerequisite " << p
-                 << " is static object";
+          if (lt != otype::a)
+            fail << "obja{} as prerequisite of " << t;
 
           seen_obj = seen_obj || true;
         }
-        else if (p.is_a<objso> () ||
-                 p.is_a<obj> ())
+        else if (p.is_a<objs> ())
         {
+          if (lt != otype::s)
+            fail << "objs{} as prerequisite of " << t;
+
           seen_obj = seen_obj || true;
         }
-        else if (p.is_a<liba> ()  ||
-                 p.is_a<libso> () ||
-                 p.is_a<lib> ())
+        else if (p.is_a<lib> ()  ||
+                 p.is_a<liba> () ||
+                 p.is_a<libs> ())
         {
           seen_lib = seen_lib || true;
         }
@@ -530,7 +491,7 @@ namespace build2
       // "library meta-information protocol". Don't do this if we are
       // called from the install rule just to check if we would match.
       //
-      if (seen_lib && lt != type::e &&
+      if (seen_lib && lt != otype::e &&
           a.operation () != install_id && a.outer_operation () != install_id)
       {
         if (t.group != nullptr)
@@ -540,7 +501,7 @@ namespace build2
 
         for (prerequisite_member p: group_prerequisite_members (a, t))
         {
-          if (p.is_a<lib> () || p.is_a<liba> () || p.is_a<libso> ())
+          if (p.is_a<lib> () || p.is_a<liba> () || p.is_a<libs> ())
           {
             target* pt (nullptr);
 
@@ -583,9 +544,8 @@ namespace build2
       const string& tsys (cast<string> (rs["cxx.target.system"]));
       const string& tclass (cast<string> (rs["cxx.target.class"]));
 
-      type lt (link_type (t));
-      order lo (link_order (t));
-      bool so (lt == type::so);
+      otype lt (link_type (t));
+      lorder lo (link_order (bs, lt));
 
       // Derive file name from target name.
       //
@@ -596,7 +556,7 @@ namespace build2
 
         switch (lt)
         {
-        case type::e:
+        case otype::e:
           {
             if (tclass == "windows")
               e = "exe";
@@ -605,7 +565,7 @@ namespace build2
 
             break;
           }
-        case type::a:
+        case otype::a:
           {
             // To be anally precise, let's use the ar id to decide how to name
             // the library in case, for example, someone wants to archive
@@ -626,7 +586,7 @@ namespace build2
 
             break;
           }
-        case type::so:
+        case otype::s:
           {
             //@@ VC: DLL name.
 
@@ -637,9 +597,9 @@ namespace build2
             }
             else if (tclass == "windows")
             {
-              // On Windows libso{} is an ad hoc group. The libso{} itself is
+              // On Windows libs{} is an ad hoc group. The libs{} itself is
               // the import library and we add dll{} as a member (see below).
-              // While at first it may seem strange that libso{} is the import
+              // While at first it may seem strange that libs{} is the import
               // library and not the DLL, if you meditate on it, you will see
               // it makes a lot of sense: our main task here is building and
               // for that we need the import library, not the DLL.
@@ -697,7 +657,7 @@ namespace build2
       {
         // DLL
         //
-        if (so)
+        if (lt == otype::s)
         {
           file& dll (add_adhoc (t, "dll"));
 
@@ -707,7 +667,7 @@ namespace build2
 
         // PDB
         //
-        if (lt != type::a &&
+        if (lt != otype::a &&
             cid == "msvc" &&
             find_option ("/DEBUG", t, "cxx.loptions", true))
         {
@@ -734,6 +694,10 @@ namespace build2
       // When cleaning, ignore prerequisites that are not in the same
       // or a subdirectory of our project root.
       //
+      const target_type& ott (lt == otype::e ? obje::static_type :
+                              lt == otype::a ? obja::static_type :
+                              objs::static_type);
+
       for (prerequisite_member p: group_prerequisite_members (a, t))
       {
         target* pt (nullptr);
@@ -758,11 +722,15 @@ namespace build2
           //
           if (obj* o = pt->is_a<obj> ())
           {
-            pt = so ? static_cast<target*> (o->so) : o->a;
+            switch (lt)
+            {
+            case otype::e: pt = o->e; break;
+            case otype::a: pt = o->a; break;
+            case otype::s: pt = o->s; break;
+            }
 
             if (pt == nullptr)
-              pt = &search (so ? objso::static_type : obja::static_type,
-                            p.key ());
+              pt = &search (ott, p.key ());
           }
           else if (lib* l = pt->is_a<lib> ())
           {
@@ -785,10 +753,7 @@ namespace build2
         bool group (!p.prerequisite.belongs (t)); // Group's prerequisite.
 
         const prerequisite_key& cp (p.key ()); // c(xx){} prerequisite key.
-        const target_type& otype (
-          group
-          ? obj::static_type
-          : (so ? objso::static_type : obja::static_type));
+        const target_type& tt (group ? obj::static_type : ott);
 
         // Come up with the obj*{} target. The c(xx){} prerequisite directory
         // can be relative (to the scope) or absolute. If it is relative, then
@@ -807,7 +772,7 @@ namespace build2
           {
             if (!cpd.sub (rs.src_path ()))
               fail << "out of project prerequisite " << cp <<
-                info << "specify corresponding " << otype.name << "{} "
+                info << "specify corresponding " << tt.name << "{} "
                    << "target explicitly";
 
             d = rs.out_path () / cpd.leaf (rs.src_path ());
@@ -817,7 +782,7 @@ namespace build2
         // obj*{} is always in the out tree.
         //
         target& ot (
-          search (otype, d, dir_path (), *cp.tk.name, nullptr, cp.scope));
+          search (tt, d, dir_path (), *cp.tk.name, nullptr, cp.scope));
 
         // If we are cleaning, check that this target is in the same or
         // a subdirectory of our project root.
@@ -838,11 +803,16 @@ namespace build2
         if (group)
         {
           obj& o (static_cast<obj&> (ot));
-          pt = so ? static_cast<target*> (o.so) : o.a;
+
+          switch (lt)
+          {
+          case otype::e: pt = o.e; break;
+          case otype::a: pt = o.a; break;
+          case otype::s: pt = o.s; break;
+          }
 
           if (pt == nullptr)
-            pt = &search (so ? objso::static_type : obja::static_type,
-                          o.dir, o.out, o.name, o.ext, nullptr);
+            pt = &search (ott, o.dir, o.out, o.name, o.ext, nullptr);
         }
         else
           pt = &ot;
@@ -869,9 +839,9 @@ namespace build2
               (p.is_a<cxx> () && (p1.is_a<hxx> () ||
                                   p1.is_a<ixx> () ||
                                   p1.is_a<txx> ())) ||
-              p1.is_a<lib> ()  ||
+              p1.is_a<lib>  () ||
               p1.is_a<liba> () ||
-              p1.is_a<libso> ())
+              p1.is_a<libs> ())
           {
             continue;
           }
@@ -893,7 +863,7 @@ namespace build2
                    << "be incompatible with existing target " << *pt <<
                 info << "existing prerequisite " << p1 << " does not match "
                    << cp <<
-                info << "specify corresponding " << otype.name << "{} target "
+                info << "specify corresponding " << tt.name << "{} target "
                    << "explicitly";
 
             found = true;
@@ -918,7 +888,7 @@ namespace build2
           //
           for (prerequisite& p: group_prerequisites (t))
           {
-            if (p.is_a<lib> () || p.is_a<liba> () || p.is_a<libso> ())
+            if (p.is_a<lib> () || p.is_a<liba> () || p.is_a<libs> ())
               ot.prerequisites.emplace_back (p);
           }
 
@@ -948,7 +918,7 @@ namespace build2
           args.push_back (relative (pa->path ()).string ()); // string()&&
           append_libraries (args, *pa);
         }
-        else if (libso* ps = pt->is_a<libso> ())
+        else if (libs* ps = pt->is_a<libs> ())
           args.push_back (relative (ps->path ()).string ()); // string()&&
       }
     }
@@ -963,17 +933,17 @@ namespace build2
           cs.append (pa->path ().string ());
           hash_libraries (cs, *pa);
         }
-        else if (libso* ps = pt->is_a<libso> ())
+        else if (libs* ps = pt->is_a<libs> ())
           cs.append (ps->path ().string ());
       }
     }
 
     static void
-    append_rpath_link (strings& args, libso& t)
+    append_rpath_link (strings& args, libs& t)
     {
       for (target* pt: t.prerequisite_targets)
       {
-        if (libso* ls = pt->is_a<libso> ())
+        if (libs* ls = pt->is_a<libs> ())
         {
           args.push_back ("-Wl,-rpath-link," +
                           ls->path ().directory ().string ());
@@ -1002,8 +972,7 @@ namespace build2
 
       file& t (static_cast<file&> (xt));
 
-      type lt (link_type (t));
-      bool so (lt == type::so);
+      otype lt (link_type (t));
 
       // Update prerequisites.
       //
@@ -1020,7 +989,7 @@ namespace build2
       path manifest; // Manifest itself (msvc) or compiled object file.
       timestamp rpath_timestamp (timestamp_nonexistent); // DLLs timestamp.
 
-      if (lt == type::e && tclass == "windows")
+      if (lt == otype::e && tclass == "windows")
       {
         // First determine if we need to add our rpath emulating assembly. The
         // assembly itself is generated later, after updating the target. Omit
@@ -1130,7 +1099,7 @@ namespace build2
 
       // Then the linker checksum (ar/ranlib or C++ compiler).
       //
-      if (lt == type::a)
+      if (lt == otype::a)
       {
         ranlib = rs["config.bin.ranlib"];
 
@@ -1195,7 +1164,7 @@ namespace build2
         args.push_back (m);
       }
 
-      if (lt == type::a)
+      if (lt == otype::a)
       {
         if (cid == "msvc") ;
         else
@@ -1238,7 +1207,7 @@ namespace build2
         {
           // Set soname.
           //
-          if (so)
+          if (lt == otype::s)
           {
             const string& leaf (t.path ().leaf ().string ());
 
@@ -1277,7 +1246,7 @@ namespace build2
           //
           for (target* pt: t.prerequisite_targets)
           {
-            if (libso* ls = pt->is_a<libso> ())
+            if (libs* ls = pt->is_a<libs> ())
             {
               if (a.outer_operation () != install_id)
               {
@@ -1330,11 +1299,12 @@ namespace build2
           path_target* ppt;
           liba* a (nullptr);
 
-          if ((ppt = pt->is_a<obja> ())  ||
-              (ppt = pt->is_a<objso> ()) ||
-              (lt != type::a &&
+          if ((ppt = pt->is_a<obje> ()) ||
+              (ppt = pt->is_a<obja> ()) ||
+              (ppt = pt->is_a<objs> ()) ||
+              (lt != otype::a &&
                ((ppt = a = pt->is_a<liba> ()) ||
-                (ppt = pt->is_a<libso> ()))))
+                (ppt =     pt->is_a<libs> ()))))
           {
             cs.append (ppt->path ().string ());
 
@@ -1353,7 +1323,7 @@ namespace build2
 
         // Treat them as inputs, not options.
         //
-        if (lt != type::a)
+        if (lt != otype::a)
           hash_options (cs, t, "cxx.libs");
 
         if (dd.expect (cs.string ()) != nullptr)
@@ -1387,7 +1357,7 @@ namespace build2
 
       switch (lt)
       {
-      case type::e:
+      case otype::e:
         {
           if (cid == "msvc")
           {
@@ -1449,7 +1419,7 @@ namespace build2
 
           break;
         }
-      case type::a:
+      case otype::a:
         {
           args[0] = cast<path> (rs["config.bin.ar"]).string ().c_str ();
 
@@ -1470,7 +1440,7 @@ namespace build2
 
           break;
         }
-      case type::so:
+      case otype::s:
         {
           if (cid == "msvc")
           {
@@ -1489,7 +1459,7 @@ namespace build2
 
             if (tsys == "mingw32")
             {
-              // On Windows libso{} is the import stub and its first ad hoc
+              // On Windows libs{} is the import stub and its first ad hoc
               // group member is dll{}.
               //
               out = "-Wl,--out-implib=" + relt.string ();
@@ -1514,13 +1484,13 @@ namespace build2
       {
         path_target* ppt;
         liba* a (nullptr);
-        libso* so (nullptr);
 
-        if ((ppt = pt->is_a<obja> ())  ||
-            (ppt = pt->is_a<objso> ()) ||
-            (lt != type::a &&
+        if ((ppt = pt->is_a<obje> ()) ||
+            (ppt = pt->is_a<obja> ()) ||
+            (ppt = pt->is_a<objs> ()) ||
+            (lt != otype::a &&
              ((ppt = a = pt->is_a<liba> ()) ||
-              (ppt = so = pt->is_a<libso> ()))))
+              (ppt     = pt->is_a<libs> ()))))
         {
           sargs.push_back (relative (ppt->path ()).string ()); // string()&&
 
@@ -1543,7 +1513,7 @@ namespace build2
       for (size_t i (0); i != sargs.size (); ++i)
         args.push_back (sargs[i].c_str ());
 
-      if (lt != type::a)
+      if (lt != otype::a)
         append_options (args, t, "cxx.libs");
 
       args.push_back (nullptr);
@@ -1615,7 +1585,7 @@ namespace build2
       // For Windows generate rpath-emulating assembly (unless updaing for
       // install).
       //
-      if (lt == type::e && tclass == "windows")
+      if (lt == otype::e && tclass == "windows")
       {
         if (a.outer_operation () != install_id)
           windows_rpath_assembly (t, rpath_timestamp, scratch);
@@ -1644,12 +1614,12 @@ namespace build2
 
       switch (link_type (t))
       {
-      case type::a:
+      case otype::a:
         {
           e = {"+.d"};
           break;
         }
-      case type::e:
+      case otype::e:
         {
           if (tclass == "windows")
           {
@@ -1671,7 +1641,7 @@ namespace build2
 
           break;
         }
-      case type::so:
+      case otype::s:
         {
           e = {"+.d"};
           break;
diff --git a/build2/cxx/module.cxx b/build2/cxx/module.cxx
index 6a5469c..69e76a3 100644
--- a/build2/cxx/module.cxx
+++ b/build2/cxx/module.cxx
@@ -316,38 +316,40 @@ namespace build2
 
         auto& r (b.rules);
 
-        r.insert<obja> (perform_update_id, "cxx.compile", compile::instance);
+        r.insert<obje> (perform_update_id, "cxx.compile", compile::instance);
+        r.insert<obje> (perform_clean_id, "cxx.compile", compile::instance);
 
         r.insert<obja> (perform_update_id, "cxx.compile", compile::instance);
         r.insert<obja> (perform_clean_id, "cxx.compile", compile::instance);
 
-        r.insert<objso> (perform_update_id, "cxx.compile", compile::instance);
-        r.insert<objso> (perform_clean_id, "cxx.compile", compile::instance);
+        r.insert<objs> (perform_update_id, "cxx.compile", compile::instance);
+        r.insert<objs> (perform_clean_id, "cxx.compile", compile::instance);
 
-        r.insert<exe> (perform_update_id, "cxx.link", link::instance);
-        r.insert<exe> (perform_clean_id, "cxx.link", link::instance);
+        r.insert<exe>  (perform_update_id, "cxx.link", link::instance);
+        r.insert<exe>  (perform_clean_id, "cxx.link", link::instance);
 
         r.insert<liba> (perform_update_id, "cxx.link", link::instance);
         r.insert<liba> (perform_clean_id, "cxx.link", link::instance);
 
-        r.insert<libso> (perform_update_id, "cxx.link", link::instance);
-        r.insert<libso> (perform_clean_id, "cxx.link", link::instance);
+        r.insert<libs> (perform_update_id, "cxx.link", link::instance);
+        r.insert<libs> (perform_clean_id, "cxx.link", link::instance);
 
-        // Register for configure so that we detect unresolved imports
-        // during configuration rather that later, e.g., during update.
+        // Register for configure so that we detect unresolved imports during
+        // configuration rather that later, e.g., during update.
         //
+        r.insert<obje> (configure_update_id, "cxx.compile", compile::instance);
         r.insert<obja> (configure_update_id, "cxx.compile", compile::instance);
-        r.insert<objso> (configure_update_id, "cxx.compile", compile::instance);
+        r.insert<objs> (configure_update_id, "cxx.compile", compile::instance);
 
-        r.insert<exe> (configure_update_id, "cxx.link", link::instance);
+        r.insert<exe>  (configure_update_id, "cxx.link", link::instance);
         r.insert<liba> (configure_update_id, "cxx.link", link::instance);
-        r.insert<libso> (configure_update_id, "cxx.link", link::instance);
+        r.insert<libs> (configure_update_id, "cxx.link", link::instance);
 
         //@@ Should we check if install module was loaded (see bin)?
         //
-        r.insert<exe> (perform_install_id, "cxx.install", install::instance);
+        r.insert<exe>  (perform_install_id, "cxx.install", install::instance);
         r.insert<liba> (perform_install_id, "cxx.install", install::instance);
-        r.insert<libso> (perform_install_id, "cxx.install", install::instance);
+        r.insert<libs> (perform_install_id, "cxx.install", install::instance);
       }
 
       // Configure "installability" of our target types.
diff --git a/build2/cxx/utility.cxx b/build2/cxx/utility.cxx
index ed57fd2..cf9c4d0 100644
--- a/build2/cxx/utility.cxx
+++ b/build2/cxx/utility.cxx
@@ -79,7 +79,7 @@ namespace build2
 
       for (target* t: l.prerequisite_targets)
       {
-        if (t->is_a<lib> () || t->is_a<liba> () || t->is_a<libso> ())
+        if (t->is_a<lib> () || t->is_a<liba> () || t->is_a<libs> ())
           append_lib_options (args, *t, var);
       }
 
@@ -93,7 +93,7 @@ namespace build2
 
       for (target* t: l.prerequisite_targets)
       {
-        if (t->is_a<lib> () || t->is_a<liba> () || t->is_a<libso> ())
+        if (t->is_a<lib> () || t->is_a<liba> () || t->is_a<libs> ())
           hash_lib_options (csum, *t, var);
       }
 
diff --git a/build2/cxx/windows-rpath.cxx b/build2/cxx/windows-rpath.cxx
index 8f19f79..0bd4bc5 100644
--- a/build2/cxx/windows-rpath.cxx
+++ b/build2/cxx/windows-rpath.cxx
@@ -49,7 +49,7 @@ namespace build2
 
       for (target* pt: t.prerequisite_targets)
       {
-        if (libso* ls = pt->is_a<libso> ())
+        if (libs* ls = pt->is_a<libs> ())
         {
           // This can be an installed library in which case we will have just
           // the import stub but may also have just the DLL. For now we don't
@@ -84,7 +84,7 @@ namespace build2
     {
       for (target* pt: t.prerequisite_targets)
       {
-        if (libso* ls = pt->is_a<libso> ())
+        if (libs* ls = pt->is_a<libs> ())
         {
           if (ls->member == nullptr)
             continue;