Use match options for runtime/buildtime distinction when installing libraries

Specifically, now, if a library is installed solely as a prerequisite of
an executable (potentially recursively), then only its runtime files are
installed omitting everything buildtime-related (static/import libraries,
non-versioned symlinks for shared libraries, pkg-config files, headers,
etc). If you are familiar with the runtime and -dev/-devel package splits
for libraries in Debian/Fedora, this is an analogous semantics.

8 files changed, 837 insertions, 201 deletions

diff --git a/libbuild2/bash/rule.cxx b/libbuild2/bash/rule.cxx
index 502a206..6e96b34 100644
--- a/libbuild2/bash/rule.cxx
+++ b/libbuild2/bash/rule.cxx
@@ -455,9 +455,9 @@ namespace build2
     }
 
     recipe install_rule::
-    apply (action a, target& t) const
+    apply (action a, target& t, match_extra& me) const
     {
-      recipe r (file_rule::apply_impl (a, t));
+      recipe r (file_rule::apply_impl (a, t, me));
 
       if (r == nullptr)
         return noop_recipe;
diff --git a/libbuild2/bash/rule.hxx b/libbuild2/bash/rule.hxx
index 444d176..3f9618f 100644
--- a/libbuild2/bash/rule.hxx
+++ b/libbuild2/bash/rule.hxx
@@ -74,7 +74,7 @@ namespace build2
       match (action, target&) const override;
 
       virtual recipe
-      apply (action, target&) const override;
+      apply (action, target&, match_extra&) const override;
 
     protected:
       const in_rule& in_;
diff --git a/libbuild2/bin/target.hxx b/libbuild2/bin/target.hxx
index 9685e39..8f2a92e 100644
--- a/libbuild2/bin/target.hxx
+++ b/libbuild2/bin/target.hxx
@@ -412,6 +412,21 @@ namespace build2
       virtual group_view
       group_members (action) const override;
 
+      // Match options for the install operation on the liba{}/libs{} and
+      // libua{}/libus{} target types (note: not lib{}/libul{} nor libue{}).
+      //
+      // If only install_runtime option is specified, then only install the
+      // runtime files omitting everything buildtime (headers, pkg-config
+      // files, shared library version-related symlinks, etc).
+      //
+      // Note that it's either runtime-only or runtime and buildtime (i.e.,
+      // everything), so match with install_all instead of install_buildtime
+      // (the latter is only useful in the rule implementations).
+      //
+      static constexpr uint64_t option_install_runtime   = 0x01;
+      static constexpr uint64_t option_install_buildtime = 0x02;
+      static constexpr uint64_t option_install_all = match_extra::all_options;
+
     public:
       static const target_type static_type;
     };
diff --git a/libbuild2/cc/install-rule.cxx b/libbuild2/cc/install-rule.cxx
index 3eaaa94..7327711 100644
--- a/libbuild2/cc/install-rule.cxx
+++ b/libbuild2/cc/install-rule.cxx
@@ -24,14 +24,58 @@ namespace build2
     install_rule (data&& d, const link_rule& l)
         : common (move (d)), link_ (l) {}
 
-    const target* install_rule::
+    // Wrap the file_rule's recipe into a data-carrying recipe.
+    //
+    struct install_match_data
+    {
+      build2::recipe        recipe;
+      uint64_t              options; // Match options.
+      link_rule::libs_paths libs_paths;
+
+      target_state
+      operator() (action a, const target& t)
+      {
+        return recipe (a, t);
+      }
+    };
+
+    bool install_rule::
+    filter (action a, const target& t, const target& m) const
+    {
+      if (!t.is_a<exe> ())
+      {
+        // If runtime-only, filter out all known buildtime target types.
+        //
+        const auto& md (t.data<install_match_data> (a));
+
+        if ((md.options & lib::option_install_buildtime) == 0)
+        {
+          if (m.is_a<liba> () || // Staic library.
+              m.is_a<pc> ()   || // pkg-config file.
+              m.is_a<libi> ())   // Import library.
+            return false;
+        }
+      }
+
+      return true;
+    }
+
+    pair<const target*, uint64_t> install_rule::
     filter (const scope* is,
-            action a, const target& t, prerequisite_iterator& i) const
+            action a, const target& t, prerequisite_iterator& i,
+            match_extra& me) const
     {
       // NOTE: see libux_install_rule::filter() if changing anything here.
 
       const prerequisite& p (i->prerequisite);
 
+      uint64_t options (match_extra::all_options);
+
+      otype ot (link_type (t).type);
+
+      // @@ TMP: drop eventually.
+      //
+#if 0
       // If this is a shared library prerequisite, install it as long as it is
       // in the installation scope.
       //
@@ -43,7 +87,6 @@ namespace build2
       //
       // Note: we install ad hoc prerequisites by default.
       //
-      otype ot (link_type (t).type);
 
       // Note: at least one must be true since we only register this rule for
       // exe{}, and lib[as]{} (this makes sure the following if-condition will
@@ -64,26 +107,115 @@ namespace build2
         if (const libx* l = pt->is_a<libx> ())
           pt = link_member (*l, a, link_info (t.base_scope (), ot));
 
-        // Note: not redundant since we are returning a member.
+        // Note: not redundant since we could be returning a member.
         //
         if ((st && pt->is_a<libs> ()) || (at && pt->is_a<liba> ()))
-          return is == nullptr || pt->in (*is) ? pt : nullptr;
+        {
+          // Adjust match options.
+          //
+          if (a.operation () != update_id)
+          {
+            if (t.is_a<exe> ())
+              options = lib::option_install_runtime;
+            else
+            {
+              // This is a library prerequisite of a library target and
+              // runtime-only begets runtime-only.
+              //
+              if (me.cur_options == lib::option_install_runtime)
+                options = lib::option_install_runtime;
+            }
+          }
+
+          return make_pair (is == nullptr || pt->in (*is) ? pt : nullptr,
+                            options);
+        }
 
         // See through to libu*{} members. Note that we are always in the same
         // project (and thus amalgamation).
         //
         if (pt->is_a<libux> ())
-          return pt;
+        {
+          // Adjust match options (similar to above).
+          //
+          if (a.operation () != update_id && !pt->is_a<libue> ())
+          {
+            if (t.is_a<exe> ())
+              options = lib::option_install_runtime;
+            else
+            {
+              if (me.cur_options == lib::option_install_runtime)
+                options = lib::option_install_runtime;
+            }
+          }
+
+          return make_pair (pt, options);
+        }
       }
+#else
+      // Note that at first it may seem like we don't need to install static
+      // library prerequisites of executables. But such libraries may still
+      // have prerequisites that are needed at runtime (say, some data files).
+      // So we install all libraries as long as they are in the installation
+      // scope and deal with runtime vs buildtime distiction using match
+      // options.
+      //
+      // Note: for now we assume these prerequisites never come from see-
+      // through groups.
+      //
+      // Note: we install ad hoc prerequisites by default.
+      //
+      if (p.is_a<libx> () || p.is_a<libs> () || p.is_a<liba> ())
+      {
+        const target* pt (&search (t, p));
+
+        // If this is the lib{}/libu*{} group, pick a member which we would
+        // link. For libu*{} we want the "see through" logic.
+        //
+        if (const libx* l = pt->is_a<libx> ())
+          pt = link_member (*l, a, link_info (t.base_scope (), ot));
+
+        // Adjust match options.
+        //
+        if (a.operation () != update_id)
+        {
+          if (t.is_a<exe> ())
+            options = lib::option_install_runtime;
+          else
+          {
+            // This is a library prerequisite of a library target and
+            // runtime-only begets runtime-only.
+            //
+            if (me.cur_options == lib::option_install_runtime)
+              options = lib::option_install_runtime;
+          }
+        }
+
+        // Note: not redundant since we could be returning a member.
+        //
+        if (pt->is_a<libs> () || pt->is_a<liba> ())
+        {
+          return make_pair (is == nullptr || pt->in (*is) ? pt : nullptr,
+                            options);
+        }
+        else // libua{} or libus{}
+        {
+          // See through to libu*{} members. Note that we are always in the
+          // same project (and thus amalgamation).
+          //
+          return make_pair (pt, options);
+        }
+      }
+#endif
 
       // The rest of the tests only succeed if the base filter() succeeds.
       //
-      const target* pt (file_rule::filter (is, a, t, p));
+      const target* pt (file_rule::filter (is, a, t, p, me).first);
       if (pt == nullptr)
-        return pt;
+        return make_pair (pt, options);
 
-      // Don't install executable's prerequisite headers and module
-      // interfaces.
+      // Don't install executable's or runtime-only library's prerequisite
+      // headers and module interfaces.
       //
       // Note that if they come from a group, then we assume the entire
       // group is not to be installed.
@@ -100,7 +232,9 @@ namespace build2
                 (x_obj != nullptr && p.is_a (*x_obj)));
       };
 
-      if (t.is_a<exe> ())
+      if (t.is_a<exe> () ||
+          (a.operation () != update_id &&
+           me.cur_options == lib::option_install_runtime))
       {
         if (header_source (p))
           pt = nullptr;
@@ -115,7 +249,7 @@ namespace build2
         }
 
         if (pt == nullptr)
-          return pt;
+          return make_pair (pt, options);
       }
 
       // Here is a problem: if the user spells the obj*/bmi*{} targets
@@ -145,16 +279,16 @@ namespace build2
           {
             pt = t.is_a<exe> ()
               ? nullptr
-              : file_rule::filter (is, a, *pt, pm.prerequisite);
+              : file_rule::filter (is, a, *pt, pm.prerequisite, me).first;
             break;
           }
         }
 
         if (pt == nullptr)
-          return pt;
+          return make_pair (pt, options);
       }
 
-      return pt;
+      return make_pair (pt, options);
     }
 
     bool install_rule::
@@ -167,27 +301,34 @@ namespace build2
         file_rule::match (a, t);
     }
 
-    // Wrap the file_rule's recipe into a data-carrying recipe.
-    //
-    struct install_match_data
+    recipe install_rule::
+    apply (action a, target& t, match_extra& me) const
     {
-      build2::recipe        recipe;
-      link_rule::libs_paths libs_paths;
-
-      target_state
-      operator() (action a, const target& t)
+      // Handle match options.
+      //
+      // Do it before calling apply_impl() since we need this information
+      // in the filter() callbacks.
+      //
+      if (a.operation () != update_id)
       {
-        return recipe (a, t);
+        if (!t.is_a<exe> ())
+        {
+          if (me.new_options == 0)
+            me.new_options = lib::option_install_runtime; // Minimum we can do.
+
+          me.cur_options = me.new_options;
+        }
       }
-    };
 
-    recipe install_rule::
-    apply (action a, target& t) const
-    {
-      recipe r (file_rule::apply_impl (a, t));
+      recipe r (file_rule::apply_impl (
+                  a, t, me,
+                  me.cur_options != match_extra::all_options /* reapply */));
 
       if (r == nullptr)
+      {
+        me.cur_options = match_extra::all_options; // Noop for all options.
         return noop_recipe;
+      }
 
       if (a.operation () == update_id)
       {
@@ -209,29 +350,72 @@ namespace build2
       }
       else // install or uninstall
       {
-        // Derive shared library paths and cache them in the target's aux
-        // storage if we are un/installing (used in the *_extra() functions
-        // below).
-        //
-        if (file* f = t.is_a<libs> ())
+        file* ls;
+        if ((ls = t.is_a<libs> ()) || t.is_a<liba> ())
         {
-          if (!f->path ().empty ()) // Not binless.
+          // Derive shared library paths and cache them in the target's aux
+          // storage if we are un/installing (used in the *_extra() functions
+          // below).
+          //
+          link_rule::libs_paths lsp;
+          if (ls != nullptr && !ls->path ().empty ()) // Not binless.
           {
             const string* p (cast_null<string> (t["bin.lib.prefix"]));
             const string* s (cast_null<string> (t["bin.lib.suffix"]));
 
-            return install_match_data {
-              move (r),
-              link_.derive_libs_paths (*f,
-                                       p != nullptr ? p->c_str (): nullptr,
-                                       s != nullptr ? s->c_str (): nullptr)};
+            lsp = link_.derive_libs_paths (*ls,
+                                           p != nullptr ? p->c_str (): nullptr,
+                                           s != nullptr ? s->c_str (): nullptr);
           }
+
+          return install_match_data {move (r), me.cur_options, move (lsp)};
         }
       }
 
       return r;
     }
 
+    void install_rule::
+    reapply (action a, target& t, match_extra& me) const
+    {
+      tracer trace ("cc::install_rule::reapply");
+
+      assert (a.operation () != update_id && !t.is_a<exe> ());
+
+      l6 ([&]{trace << "rematching " << t
+                    << ", current options " << me.cur_options
+                    << ", new options " << me.new_options;});
+
+      me.cur_options |= me.new_options;
+
+      // We also need to update options in install_match_data.
+      //
+      t.data<install_match_data> (a).options = me.cur_options;
+
+      if ((me.new_options & lib::option_install_buildtime) != 0)
+      {
+        // If we are rematched with the buildtime option, propagate it to our
+        // prerequisite libraries.
+        //
+        for (const target* pt: t.prerequisite_targets[a])
+        {
+          if (pt != nullptr && (pt->is_a<liba> ()  || pt->is_a<libs> () ||
+                                pt->is_a<libua> () || pt->is_a<libus> ()))
+          {
+            // Go for all options instead of just install_buildtime to avoid
+            // any further relocking/reapply (we only support runtime-only or
+            // everything).
+            //
+            rematch_sync (a, *pt, match_extra::all_options);
+          }
+        }
+
+        // Also match any additional prerequisites (e.g., headers).
+        //
+        file_rule::reapply_impl (a, t, me);
+      }
+    }
+
     bool install_rule::
     install_extra (const file& t, const install_dir& id) const
     {
@@ -239,10 +423,15 @@ namespace build2
 
       if (t.is_a<libs> ())
       {
+        const auto& md (t.data<install_match_data> (perform_install_id));
+
         // Here we may have a bunch of symlinks that we need to install.
         //
+        // Note that for runtime-only install we only omit the name that is
+        // used for linking (e.g., libfoo.so).
+        //
         const scope& rs (t.root_scope ());
-        auto& lp (t.data<install_match_data> (perform_install_id).libs_paths);
+        const link_rule::libs_paths& lp (md.libs_paths);
 
         auto ln = [&t, &rs, &id] (const path& f, const path& l)
         {
@@ -260,7 +449,10 @@ namespace build2
         if (!in.empty ()) {r = ln (*f, in) || r; f = &in;}
         if (!so.empty ()) {r = ln (*f, so) || r; f = &so;}
         if (!ld.empty ()) {r = ln (*f, ld) || r; f = &ld;}
-        if (!lk.empty ()) {r = ln (*f, lk) || r;         }
+        if ((md.options & lib::option_install_buildtime) != 0)
+        {
+          if (!lk.empty ()) {r = ln (*f, lk) || r;}
+        }
       }
 
       return r;
@@ -273,10 +465,12 @@ namespace build2
 
       if (t.is_a<libs> ())
       {
+        const auto& md (t.data<install_match_data> (perform_uninstall_id));
+
         // Here we may have a bunch of symlinks that we need to uninstall.
         //
         const scope& rs (t.root_scope ());
-        auto& lp (t.data<install_match_data> (perform_uninstall_id).libs_paths);
+        const link_rule::libs_paths& lp (md.libs_paths);
 
         auto rm = [&rs, &id] (const path& f, const path& l)
         {
@@ -293,7 +487,10 @@ namespace build2
         if (!in.empty ()) {r = rm (*f, in) || r; f = &in;}
         if (!so.empty ()) {r = rm (*f, so) || r; f = &so;}
         if (!ld.empty ()) {r = rm (*f, ld) || r; f = &ld;}
-        if (!lk.empty ()) {r = rm (*f, lk) || r;         }
+        if ((md.options & lib::option_install_buildtime) != 0)
+        {
+          if (!lk.empty ()) {r = rm (*f, lk) || r;}
+        }
       }
 
       return r;
@@ -305,20 +502,27 @@ namespace build2
     libux_install_rule (data&& d, const link_rule& l)
         : common (move (d)), link_ (l) {}
 
-    const target* libux_install_rule::
+    pair<const target*, uint64_t> libux_install_rule::
     filter (const scope* is,
-            action a, const target& t, prerequisite_iterator& i) const
+            action a, const target& t, prerequisite_iterator& i,
+            match_extra& me) const
     {
       using file_rule = install::file_rule;
 
       const prerequisite& p (i->prerequisite);
 
+      uint64_t options (match_extra::all_options);
+
+      otype ot (link_type (t).type);
+
       // The "see through" semantics that should be parallel to install_rule
       // above. In particular, here we use libue/libua/libus{} as proxies for
       // exe/liba/libs{} there.
       //
-      otype ot (link_type (t).type);
 
+      // @@ TMP: drop eventually.
+      //
+#if 0
       bool st (t.is_a<libue> () || t.is_a<libus> ()); // Target needs shared.
       bool at (t.is_a<libua> () || t.is_a<libus> ()); // Target needs static.
       assert (st || at);
@@ -332,15 +536,70 @@ namespace build2
           pt = link_member (*l, a, link_info (t.base_scope (), ot));
 
         if ((st && pt->is_a<libs> ()) || (at && pt->is_a<liba> ()))
-          return is == nullptr || pt->in (*is) ? pt : nullptr;
+        {
+          if (a.operation () != update_id)
+          {
+            if (t.is_a<libue> ())
+              options = lib::option_install_runtime;
+            else
+            {
+              if (me.cur_options == lib::option_install_runtime)
+                options = lib::option_install_runtime;
+            }
+          }
+
+          return make_pair (is == nullptr || pt->in (*is) ? pt : nullptr,
+                            options);
+        }
 
         if (pt->is_a<libux> ())
-          return pt;
+        {
+          if (a.operation () != update_id && !pt->is_a<libue> ())
+          {
+            if (t.is_a<libue> ())
+              options = lib::option_install_runtime;
+            else
+            {
+              if (me.cur_options == lib::option_install_runtime)
+                options = lib::option_install_runtime;
+            }
+          }
+
+          return make_pair (pt, options);
+        }
+      }
+#else
+      if (p.is_a<libx> () || p.is_a<libs> () || p.is_a<liba> ())
+      {
+        const target* pt (&search (t, p));
+
+        if (const libx* l = pt->is_a<libx> ())
+          pt = link_member (*l, a, link_info (t.base_scope (), ot));
+
+        if (a.operation () != update_id)
+        {
+          if (t.is_a<libue> ())
+            options = lib::option_install_runtime;
+          else
+          {
+            if (me.cur_options == lib::option_install_runtime)
+              options = lib::option_install_runtime;
+          }
+        }
+
+        if (pt->is_a<libs> () || pt->is_a<liba> ())
+        {
+          return make_pair (is == nullptr || pt->in (*is) ? pt : nullptr,
+                            options);
+        }
+        else
+          return make_pair (pt, options);
       }
+#endif
 
-      const target* pt (file_rule::instance.filter (is, a, t, p));
+      const target* pt (file_rule::instance.filter (is, a, t, p, me).first);
       if (pt == nullptr)
-        return pt;
+        return make_pair (pt, options);
 
       auto header_source = [this] (const auto& p)
       {
@@ -351,7 +610,9 @@ namespace build2
                 (x_obj != nullptr && p.is_a (*x_obj)));
       };
 
-      if (t.is_a<libue> ())
+      if (t.is_a<libue> () ||
+          (a.operation () != update_id &&
+           me.cur_options == lib::option_install_runtime))
       {
         if (header_source (p))
           pt = nullptr;
@@ -366,7 +627,7 @@ namespace build2
         }
 
         if (pt == nullptr)
-          return pt;
+          return make_pair (pt, options);
       }
 
       bool g (false);
@@ -382,16 +643,17 @@ namespace build2
           {
             pt = t.is_a<libue> ()
               ? nullptr
-              : file_rule::instance.filter (is, a, *pt, pm.prerequisite);
+              : file_rule::instance.filter (
+                  is, a, *pt, pm.prerequisite, me).first;
             break;
           }
         }
 
         if (pt == nullptr)
-          return pt;
+          return make_pair (pt, options);
       }
 
-      return pt;
+      return make_pair (pt, options);
     }
 
     bool libux_install_rule::
@@ -403,5 +665,49 @@ namespace build2
       return link_.sub_match (x_link, update_id, a, t, me) &&
         alias_rule::match (a, t);
     }
+
+    recipe libux_install_rule::
+    apply (action a, target& t, match_extra& me) const
+    {
+      if (a.operation () != update_id)
+      {
+        if (!t.is_a<libue> ())
+        {
+          if (me.new_options == 0)
+            me.new_options = lib::option_install_runtime;
+
+          me.cur_options = me.new_options;
+        }
+      }
+
+      return alias_rule::apply_impl (
+        a, t, me, me.cur_options != match_extra::all_options /* reapply */);
+    }
+
+    void libux_install_rule::
+    reapply (action a, target& t, match_extra& me) const
+    {
+      tracer trace ("cc::linux_install_rule::reapply");
+
+      assert (a.operation () != update_id && !t.is_a<libue> ());
+
+      l6 ([&]{trace << "rematching " << t
+                    << ", current options " << me.cur_options
+                    << ", new options " << me.new_options;});
+
+      me.cur_options |= me.new_options;
+
+      if ((me.new_options & lib::option_install_buildtime) != 0)
+      {
+        for (const target* pt: t.prerequisite_targets[a])
+        {
+          if (pt != nullptr && (pt->is_a<liba> ()  || pt->is_a<libs> () ||
+                                pt->is_a<libua> () || pt->is_a<libus> ()))
+            rematch_sync (a, *pt, match_extra::all_options);
+        }
+
+        alias_rule::reapply_impl (a, t, me);
+      }
+    }
   }
 }
diff --git a/libbuild2/cc/install-rule.hxx b/libbuild2/cc/install-rule.hxx
index 6998d63..9d9211b 100644
--- a/libbuild2/cc/install-rule.hxx
+++ b/libbuild2/cc/install-rule.hxx
@@ -20,7 +20,7 @@ namespace build2
   {
     class link_rule;
 
-    // Installation rule for exe{} and lib*{}. Here we do:
+    // Installation rule for exe{} and lib[as]{}. Here we do:
     //
     // 1. Signal to the link rule that this is update for install.
     //
@@ -28,17 +28,23 @@ namespace build2
     //
     // 3. Extra un/installation (e.g., libs{} symlinks).
     //
+    // 4. Handling runtime/buildtime match options for lib[as]{}.
+    //
     class LIBBUILD2_CC_SYMEXPORT install_rule: public install::file_rule,
                                                virtual common
     {
     public:
       install_rule (data&&, const link_rule&);
 
-      virtual const target*
+      virtual bool
+      filter (action, const target&, const target&) const override;
+
+      virtual pair<const target*, uint64_t>
       filter (const scope*,
-              action, const target&, prerequisite_iterator&) const override;
+              action, const target&, prerequisite_iterator&,
+              match_extra&) const override;
 
-      // Note: rule::match() override.
+      // Note: rule::match() override (with hint and match_extra).
       //
       virtual bool
       match (action, target&, const string&, match_extra&) const override;
@@ -46,7 +52,10 @@ namespace build2
       using file_rule::match; // Make Clang happy.
 
       virtual recipe
-      apply (action, target&) const override;
+      apply (action, target&, match_extra&) const override;
+
+      virtual void
+      reapply (action, target&, match_extra&) const override;
 
       virtual bool
       install_extra (const file&, const install_dir&) const override;
@@ -58,22 +67,24 @@ namespace build2
       const link_rule& link_;
     };
 
-    // Installation rule for libu*{}.
+    // Installation rule for libu[eas]{}.
     //
     // While libu*{} members themselves are not installable, we need to see
     // through them in case they depend on stuff that we need to install
     // (e.g., headers). Note that we use the alias_rule as a base.
     //
-    class LIBBUILD2_CC_SYMEXPORT libux_install_rule:
-      public install::alias_rule,
-      virtual common
+    class LIBBUILD2_CC_SYMEXPORT libux_install_rule: public install::alias_rule,
+                                                     virtual common
     {
     public:
       libux_install_rule (data&&, const link_rule&);
 
-      virtual const target*
+      // Note: utility libraries currently have no ad hoc members.
+
+      virtual pair<const target*, uint64_t>
       filter (const scope*,
-              action, const target&, prerequisite_iterator&) const override;
+              action, const target&, prerequisite_iterator&,
+              match_extra&) const override;
 
       // Note: rule::match() override.
       //
@@ -82,6 +93,12 @@ namespace build2
 
       using alias_rule::match; // Make Clang happy.
 
+      virtual recipe
+      apply (action, target&, match_extra&) const override;
+
+      virtual void
+      reapply (action, target&, match_extra&) const override;
+
     private:
       const link_rule& link_;
     };
diff --git a/libbuild2/cc/module.cxx b/libbuild2/cc/module.cxx
index 40857d7..eed7db1 100644
--- a/libbuild2/cc/module.cxx
+++ b/libbuild2/cc/module.cxx
@@ -1125,6 +1125,9 @@ namespace build2
         //
         if (install_loaded)
         {
+          // Note: we rely quite heavily in these rule implementations that
+          // these are the only target types they are registered for.
+
           const install_rule&  ir (*this);
 
           r.insert<exe>  (perform_install_id,   x_install, ir);
diff --git a/libbuild2/install/rule.cxx b/libbuild2/install/rule.cxx
index 4dd11e8..29888ae 100644
--- a/libbuild2/install/rule.cxx
+++ b/libbuild2/install/rule.cxx
@@ -71,27 +71,45 @@ namespace build2
       return true;
     }
 
-    const target* alias_rule::
+    pair<const target*, uint64_t> alias_rule::
     filter (const scope* is,
-            action a, const target& t, prerequisite_iterator& i) const
+            action a, const target& t, prerequisite_iterator& i,
+            match_extra& me) const
     {
       assert (i->member == nullptr);
-      return filter (is, a, t, i->prerequisite);
+      return filter (is, a, t, i->prerequisite, me);
     }
 
-    const target* alias_rule::
+    pair<const target*, uint64_t> alias_rule::
     filter (const scope* is,
-            action, const target& t, const prerequisite& p) const
+            action, const target& t, const prerequisite& p,
+            match_extra&) const
     {
       const target& pt (search (t, p));
-      return is == nullptr || pt.in (*is) ? &pt : nullptr;
+      return make_pair (is == nullptr || pt.in (*is) ? &pt : nullptr,
+                        match_extra::all_options);
     }
 
     recipe alias_rule::
-    apply (action a, target& t) const
+    apply (action a, target& t, match_extra& me) const
+    {
+      return apply_impl (a, t, me);
+    }
+
+    recipe alias_rule::
+    apply (action, target&) const
+    {
+      assert (false); // Never called.
+      return nullptr;
+    }
+
+    recipe alias_rule::
+    apply_impl (action a, target& t, match_extra& me, bool reapply) const
     {
       tracer trace ("install::alias_rule::apply");
 
+      assert (!reapply || a.operation () != update_id);
+
       // Pass-through to our installable prerequisites.
       //
       // @@ Shouldn't we do match in parallel (here and below)?
@@ -102,6 +120,8 @@ namespace build2
       auto pms (group_prerequisite_members (a, t, members_mode::never));
       for (auto i (pms.begin ()), e (pms.end ()); i != e; ++i)
       {
+        // NOTE: see essentially the same logic in reapply_impl() below.
+        //
         const prerequisite& p (i->prerequisite);
 
         // Ignore excluded.
@@ -125,13 +145,17 @@ namespace build2
         if (!is)
           is = a.operation () != update_id ? install_scope (t) : nullptr;
 
-        const target* pt (filter (*is, a, t, i));
+        pair<const target*, uint64_t> fr (filter (*is, a, t, i, me));
+
+        const target* pt (fr.first);
+        uint64_t options (fr.second);
+
+        lookup l;
+
         if (pt == nullptr)
         {
           l5 ([&]{trace << "ignoring " << p << " (filtered out)";});
-          continue;
         }
-
         // Check if this prerequisite is explicitly "not installable", that
         // is, there is the 'install' variable and its value is false.
         //
@@ -143,64 +167,108 @@ namespace build2
         //
         // Note: not the same as lookup_install() above.
         //
-        auto l ((*pt)[var_install (*p.scope.root_scope ())]);
-        if (l && cast<path> (l).string () == "false")
+        else if ((l = (*pt)[var_install (*p.scope.root_scope ())]) &&
+                 cast<path> (l).string () == "false")
         {
           l5 ([&]{trace << "ignoring " << *pt << " (not installable)";});
-          continue;
+          pt = nullptr;
         }
-
         // If this is not a file-based target (e.g., a target group such as
         // libu{}) then ignore it if there is no rule to install.
         //
-        if (pt->is_a<file> ())
-          match_sync (a, *pt);
-        else if (!try_match_sync (a, *pt).first)
+        else if (pt->is_a<file> ())
+        {
+          match_sync (a, *pt, options);
+        }
+        else if (!try_match_sync (a, *pt, options).first)
         {
           l5 ([&]{trace << "ignoring " << *pt << " (no rule)";});
           pt = nullptr;
         }
 
-        if (pt != nullptr)
-          pts.push_back (prerequisite_target (pt, pi));
+        if (pt != nullptr || reapply)
+        {
+          // Use auxiliary data for a NULL entry to distinguish between
+          // filtered out (1) and ignored for other reasons (0).
+          //
+          pts.push_back (
+            prerequisite_target (pt, pi, fr.first == nullptr ? 1 : 0));
+        }
       }
 
       return default_recipe;
     }
 
-    // fsdir_rule
-    //
-    const fsdir_rule fsdir_rule::instance;
-
-    bool fsdir_rule::
-    match (action, target&) const
+    void alias_rule::
+    reapply_impl (action a, target& t, match_extra& me) const
     {
-      // We always match.
-      //
-      // Note that we are called both as the outer part during the update-for-
-      // un/install pre-operation and as the inner part during the un/install
-      // operation itself.
-      //
-      return true;
-    }
+      tracer trace ("install::alias_rule::reapply");
 
-    recipe fsdir_rule::
-    apply (action a, target& t) const
-    {
-      // If this is outer part of the update-for-un/install, delegate to the
-      // default fsdir rule. Otherwise, this is a noop (we don't install
-      // fsdir{}).
-      //
-      // For now we also assume we don't need to do anything for prerequisites
-      // (the only sensible prerequisite of fsdir{} is another fsdir{}).
+      assert (a.operation () != update_id);
+
+      optional<const scope*> is;
+
+      // Iterate over prerequisites and prerequisite targets in parallel.
       //
-      if (a.operation () == update_id)
+      auto& pts (t.prerequisite_targets[a]);
+      size_t j (0), n (pts.size ()), en (0);
+
+      auto pms (group_prerequisite_members (a, t, members_mode::never));
+      for (auto i (pms.begin ()), e (pms.end ());
+           i != e && j != n;
+           ++i, ++j, ++en)
       {
-        match_inner (a, t);
-        return inner_recipe;
+        // The same logic as in apply() above except that we skip
+        // prerequisites that were not filtered out.
+        //
+        const prerequisite& p (i->prerequisite);
+
+        include_type pi (include (a, t, p));
+        if (!pi)
+          continue;
+
+        if (p.proj)
+          continue;
+
+        prerequisite_target& pto (pts[j]);
+
+        if (pto.target != nullptr || pto.data == 0)
+          continue;
+
+        if (!is)
+          is = a.operation () != update_id ? install_scope (t) : nullptr;
+
+        pair<const target*, uint64_t> fr (filter (*is, a, t, i, me));
+
+        const target* pt (fr.first);
+        uint64_t options (fr.second);
+
+        lookup l;
+
+        if (pt == nullptr)
+        {
+          l5 ([&]{trace << "ignoring " << p << " (filtered out)";});
+        }
+        else if ((l = (*pt)[var_install (*p.scope.root_scope ())]) &&
+                 cast<path> (l).string () == "false")
+        {
+          l5 ([&]{trace << "ignoring " << *pt << " (not installable)";});
+          pt = nullptr;
+        }
+        else if (pt->is_a<file> ())
+        {
+          match_sync (a, *pt, options);
+        }
+        else if (!try_match_sync (a, *pt, options).first)
+        {
+          l5 ([&]{trace << "ignoring " << *pt << " (no rule)";});
+          pt = nullptr;
+        }
+
+        pto = prerequisite_target (pt, pi, fr.first == nullptr ? 1 : 0);
       }
-      else
-        return noop_recipe;
+
+      assert (en == n); // Did not call apply() with true for reapply?
     }
 
     // group_rule
@@ -214,16 +282,19 @@ namespace build2
         alias_rule::match (a, t);
     }
 
-    const target* group_rule::
-    filter (action, const target&, const target& m) const
+    bool group_rule::
+    filter (action, const target&, const target&) const
     {
-      return &m;
+      return true;
     }
 
-    const target* group_rule::
+    pair<const target*, uint64_t> group_rule::
     filter (const scope* is,
-            action, const target& t, const prerequisite& p) const
+            action, const target& t, const prerequisite& p,
+            match_extra&) const
     {
+      pair<const target*, uint64_t> r (nullptr, match_extra::all_options);
+
       // The same logic as in file_rule::filter() below.
       //
       if (p.is_a<exe> ())
@@ -232,15 +303,18 @@ namespace build2
 
         if (p.vars.empty () ||
             cast_empty<path> (p.vars[var_install (rs)]).string () != "true")
-          return nullptr;
+          return r;
       }
 
       const target& pt (search (t, p));
-      return is == nullptr || pt.in (*is) ? &pt : nullptr;
+      if (is == nullptr || pt.in (*is))
+        r.first = &pt;
+
+      return r;
     }
 
     recipe group_rule::
-    apply (action a, target& t) const
+    apply (action a, target& t, match_extra& me) const
     {
       tracer trace ("install::group_rule::apply");
 
@@ -265,17 +339,16 @@ namespace build2
         auto& pts (t.prerequisite_targets[a]);
         for (size_t i (0); i != gv.count; ++i)
         {
-          const target* m (gv.members[i]);
+          const target* mt (gv.members[i]);
 
-          if (m == nullptr)
+          if (mt == nullptr)
             continue;
 
           // Let a customized rule have its say.
           //
-          const target* mt (filter (a, t, *m));
-          if (mt == nullptr)
+          if (!filter (a, t, *mt))
           {
-            l5 ([&]{trace << "ignoring " << *m << " (filtered out)";});
+            l5 ([&]{trace << "ignoring " << *mt << " (filtered out)";});
             continue;
           }
 
@@ -298,7 +371,7 @@ namespace build2
 
       // Delegate to the base rule.
       //
-      return alias_rule::apply (a, t);
+      return alias_rule::apply (a, t, me);
     }
 
 
@@ -315,18 +388,28 @@ namespace build2
       return true;
     }
 
-    const target* file_rule::
+    bool file_rule::
+    filter (action, const target&, const target&) const
+    {
+      return true;
+    }
+
+    pair<const target*, uint64_t> file_rule::
     filter (const scope* is,
-            action a, const target& t, prerequisite_iterator& i) const
+            action a, const target& t, prerequisite_iterator& i,
+            match_extra& me) const
     {
       assert (i->member == nullptr);
-      return filter (is, a, t, i->prerequisite);
+      return filter (is, a, t, i->prerequisite, me);
     }
 
-    const target* file_rule::
+    pair<const target*, uint64_t> file_rule::
     filter (const scope* is,
-            action, const target& t, const prerequisite& p) const
+            action, const target& t, const prerequisite& p,
+            match_extra&) const
     {
+      pair<const target*, uint64_t> r (nullptr, match_extra::all_options);
+
       // See also group_rule::filter() with identical semantics.
       //
       if (p.is_a<exe> ())
@@ -340,25 +423,37 @@ namespace build2
         //
         if (p.vars.empty () ||
             cast_empty<path> (p.vars[var_install (rs)]).string () != "true")
-          return nullptr;
+          return r;
       }
 
       const target& pt (search (t, p));
-      return is == nullptr || pt.in (*is) ? &pt : nullptr;
+      if (is == nullptr || pt.in (*is))
+        r.first = &pt;
+
+      return r;
     }
 
     recipe file_rule::
-    apply (action a, target& t) const
+    apply (action a, target& t, match_extra& me) const
     {
-      recipe r (apply_impl (a, t));
+      recipe r (apply_impl (a, t, me));
       return r != nullptr ? move (r) : noop_recipe;
     }
 
     recipe file_rule::
-    apply_impl (action a, target& t) const
+    apply (action, target&) const
+    {
+      assert (false); // Never called.
+      return nullptr;
+    }
+
+    recipe file_rule::
+    apply_impl (action a, target& t, match_extra& me, bool reapply) const
     {
       tracer trace ("install::file_rule::apply");
 
+      assert (!reapply || a.operation () != update_id);
+
       // Note that we are called both as the outer part during the update-for-
       // un/install pre-operation and as the inner part during the un/install
       // operation itself.
@@ -415,6 +510,8 @@ namespace build2
       auto pms (group_prerequisite_members (a, t, members_mode::never));
       for (auto i (pms.begin ()), e (pms.end ()); i != e; ++i)
       {
+        // NOTE: see essentially the same logic in reapply_impl() below.
+        //
         const prerequisite& p (i->prerequisite);
 
         // Ignore excluded.
@@ -438,27 +535,30 @@ namespace build2
         if (!is)
           is = a.operation () != update_id ? install_scope (t) : nullptr;
 
-        const target* pt (filter (*is, a, t, i));
+        pair<const target*, uint64_t> fr (filter (*is, a, t, i, me));
+
+        const target* pt (fr.first);
+        uint64_t options (fr.second);
+
+        lookup l;
 
         if (pt == nullptr)
         {
           l5 ([&]{trace << "ignoring " << p << " (filtered out)";});
-          continue;
         }
-
+        //
         // See if we were explicitly instructed not to touch this target (the
         // same semantics as in alias_rule).
         //
         // Note: not the same as lookup_install() above.
         //
-        auto l ((*pt)[var_install (*p.scope.root_scope ())]);
-        if (l && cast<path> (l).string () == "false")
+        else if ((l = (*pt)[var_install (*p.scope.root_scope ())]) &&
+                 cast<path> (l).string () == "false")
         {
           l5 ([&]{trace << "ignoring " << *pt << " (not installable)";});
-          continue;
+          pt = nullptr;
         }
-
-        if (pt->is_a<file> ())
+        else if (pt->is_a<file> ())
         {
           // If the matched rule returned noop_recipe, then the target state
           // is set to unchanged as an optimization. Use this knowledge to
@@ -466,17 +566,28 @@ namespace build2
           // when updating static installable content (headers, documentation,
           // etc).
           //
-          if (match_sync (a, *pt, unmatch::unchanged).first)
+          // Regarding options, the expectation here is that they are not used
+          // for the update operation. And for install/uninstall, if they are
+          // used, then they don't effect whether the target is unchanged. All
+          // feels reasonable.
+          //
+          if (match_sync (a, *pt, unmatch::unchanged, options).first)
             pt = nullptr;
         }
-        else if (!try_match_sync (a, *pt).first)
+        else if (!try_match_sync (a, *pt, options).first)
         {
           l5 ([&]{trace << "ignoring " << *pt << " (no rule)";});
           pt = nullptr;
         }
 
-        if (pt != nullptr)
-          pts.push_back (prerequisite_target (pt, pi));
+        if (pt != nullptr || reapply)
+        {
+          // Use auxiliary data for a NULL entry to distinguish between
+          // filtered out (1) and ignored for other reasons (0).
+          //
+          pts.push_back (
+            prerequisite_target (pt, pi, fr.first == nullptr ? 1 : 0));
+        }
       }
 
 #if 1
@@ -502,6 +613,79 @@ namespace build2
       }
     }
 
+    void file_rule::
+    reapply_impl (action a, target& t, match_extra& me) const
+    {
+      tracer trace ("install::file_rule::reapply");
+
+      assert (a.operation () != update_id);
+
+      optional<const scope*> is;
+
+      // Iterate over prerequisites and prerequisite targets in parallel.
+      //
+      auto& pts (t.prerequisite_targets[a]);
+      size_t j (0), n (pts.size ()), en (0);
+
+      auto pms (group_prerequisite_members (a, t, members_mode::never));
+      for (auto i (pms.begin ()), e (pms.end ());
+           i != e && j != n;
+           ++i, ++j, ++en)
+      {
+        // The same logic as in apply() above except that we skip
+        // prerequisites that were not filtered out.
+        //
+        const prerequisite& p (i->prerequisite);
+
+        include_type pi (include (a, t, p));
+        if (!pi)
+          continue;
+
+        if (p.proj)
+          continue;
+
+        prerequisite_target& pto (pts[j]);
+
+        if (pto.target != nullptr || pto.data == 0)
+          continue;
+
+        if (!is)
+          is = a.operation () != update_id ? install_scope (t) : nullptr;
+
+        pair<const target*, uint64_t> fr (filter (*is, a, t, i, me));
+
+        const target* pt (fr.first);
+        uint64_t options (fr.second);
+
+        lookup l;
+
+        if (pt == nullptr)
+        {
+          l5 ([&]{trace << "ignoring " << p << " (filtered out)";});
+        }
+        else if ((l = (*pt)[var_install (*p.scope.root_scope ())]) &&
+                 cast<path> (l).string () == "false")
+        {
+          l5 ([&]{trace << "ignoring " << *pt << " (not installable)";});
+          pt = nullptr;
+        }
+        else if (pt->is_a<file> ())
+        {
+          if (match_sync (a, *pt, unmatch::unchanged, options).first)
+            pt = nullptr;
+        }
+        else if (!try_match_sync (a, *pt, options).first)
+        {
+          l5 ([&]{trace << "ignoring " << *pt << " (no rule)";});
+          pt = nullptr;
+        }
+
+        pto = prerequisite_target (pt, pi, fr.first == nullptr ? 1 : 0);
+      }
+
+      assert (en == n); // Did not call apply() with true for reapply?
+    }
+
     target_state file_rule::
     perform_update (action a, const target& t)
     {
@@ -1160,6 +1344,8 @@ namespace build2
       //
       target_state r (straight_execute_prerequisites (a, t));
 
+      bool fr (filter (a, t, t));
+
       // Then installable ad hoc group members, if any.
       //
       for (const target* m (t.adhoc_member);
@@ -1170,10 +1356,13 @@ namespace build2
         {
           if (!mf->path ().empty () && mf->mtime () != timestamp_nonexistent)
           {
-            if (const path* p = lookup_install<path> (*mf, "install"))
+            if (filter (a, t, *mf))
             {
-              install_target (*mf, *p, tp.empty () ? 1 : 2);
-              r |= target_state::changed;
+              if (const path* p = lookup_install<path> (*mf, "install"))
+              {
+                install_target (*mf, *p, !fr || tp.empty () ? 1 : 2);
+                r |= target_state::changed;
+              }
             }
           }
         }
@@ -1182,7 +1371,7 @@ namespace build2
       // Finally install the target itself (since we got here we know the
       // install variable is there).
       //
-      if (!tp.empty ())
+      if (fr && !tp.empty ())
       {
         install_target (t, cast<path> (t[var_install (rs)]), 1);
         r |= target_state::changed;
@@ -1534,7 +1723,9 @@ namespace build2
       //
       target_state r (target_state::unchanged);
 
-      if (!tp.empty ())
+      bool fr (filter (a, t, t));
+
+      if (fr && !tp.empty ())
         r |= uninstall_target (t, cast<path> (t[var_install (rs)]), 1);
 
       // Then installable ad hoc group members, if any. To be anally precise,
@@ -1549,12 +1740,15 @@ namespace build2
         {
           if (!mf->path ().empty () && mf->mtime () != timestamp_nonexistent)
           {
-            if (const path* p = lookup_install<path> (*m, "install"))
+            if (filter (a, t, *mf))
             {
-              r |= uninstall_target (
-                *mf,
-                *p,
-                tp.empty () || r != target_state::changed ? 1 : 2);
+              if (const path* p = lookup_install<path> (*m, "install"))
+              {
+                r |= uninstall_target (
+                  *mf,
+                  *p,
+                  !fr || tp.empty () || r != target_state::changed ? 1 : 2);
+              }
             }
           }
         }
@@ -1566,5 +1760,40 @@ namespace build2
 
       return r;
     }
+
+    // fsdir_rule
+    //
+    const fsdir_rule fsdir_rule::instance;
+
+    bool fsdir_rule::
+    match (action, target&) const
+    {
+      // We always match.
+      //
+      // Note that we are called both as the outer part during the update-for-
+      // un/install pre-operation and as the inner part during the un/install
+      // operation itself.
+      //
+      return true;
+    }
+
+    recipe fsdir_rule::
+    apply (action a, target& t) const
+    {
+      // If this is outer part of the update-for-un/install, delegate to the
+      // default fsdir rule. Otherwise, this is a noop (we don't install
+      // fsdir{}).
+      //
+      // For now we also assume we don't need to do anything for prerequisites
+      // (the only sensible prerequisite of fsdir{} is another fsdir{}).
+      //
+      if (a.operation () == update_id)
+      {
+        match_inner (a, t);
+        return inner_recipe;
+      }
+      else
+        return noop_recipe;
+    }
   }
 }
diff --git a/libbuild2/install/rule.hxx b/libbuild2/install/rule.hxx
index b319071..b023af5 100644
--- a/libbuild2/install/rule.hxx
+++ b/libbuild2/install/rule.hxx
@@ -25,42 +25,60 @@ namespace build2
       match (action, target&) const override;
 
       // Return NULL if this prerequisite should be ignored and pointer to its
-      // target otherwise.
+      // target otherwise. In the latter case, return the match options that
+      // should be used for this prerequisite (use match_extra::all_options
+      // and not 0 if no match options are needed).
       //
       // The default implementation ignores prerequsites that are outside of
       // the installation scope (see install_scope() for details).
       //
+      // The default implementation always returns match_extra::all_options.
+      // The match_extra argument is not used by the default implementation.
+      //
       // The prerequisite is passed as an iterator allowing the filter to
       // "see" inside groups.
       //
       using prerequisite_iterator =
         prerequisite_members_range<group_prerequisites>::iterator;
 
-      virtual const target*
+      virtual pair<const target*, uint64_t>
       filter (const scope*,
-              action, const target&, prerequisite_iterator&) const;
+              action, const target&, prerequisite_iterator&,
+              match_extra&) const;
 
-      virtual const target*
-      filter (const scope*, action, const target&, const prerequisite&) const;
+      virtual pair<const target*, uint64_t>
+      filter (const scope*,
+              action, const target&, const prerequisite&,
+              match_extra&) const;
 
+      // Note: rule::apply() override (with match_extra).
+      //
       virtual recipe
-      apply (action, target&) const override;
+      apply (action, target&, match_extra&) const override;
+
+      // Implementation of apply().
+      //
+      // If the implementation may call reapply_impl(), then the reapply
+      // argument to apply_impl() must be true. Note that in this case, the
+      // *_impl() functions use the prerequisite_target::data member for own
+      // housekeeping.
+      //
+      recipe
+      apply_impl (action, target&, match_extra&, bool reapply = false) const;
+
+      // Implementation of reapply() that re-tries prerequisites that have
+      // been filtered out during the reapply() call. Note that currently not
+      // supported for update, only for install/uninstall.
+      //
+      void
+      reapply_impl (action, target&, match_extra&) const;
 
       alias_rule () {}
       static const alias_rule instance;
-    };
-
-    class fsdir_rule: public simple_rule
-    {
-    public:
-      virtual bool
-      match (action, target&) const override;
 
+    private:
       virtual recipe
-      apply (action, target&) const override;
-
-      fsdir_rule () {}
-      static const fsdir_rule instance;
+      apply (action, target&) const override; // Dummy simple_rule override.
     };
 
     // In addition to the alias rule's semantics, this rule sees through to
@@ -80,28 +98,26 @@ namespace build2
       virtual bool
       match (action, target&) const override;
 
-      // Return NULL if this group member should be ignored and pointer to its
-      // target otherwise.
+      // Return false if this group member should be ignored and true
+      // otherwise. Note that this filter is called during apply().
       //
       // The default implementation accepts all members.
       //
-      virtual const target*
+      virtual bool
       filter (action, const target&, const target& group_member) const;
 
       // Return NULL if this prerequisite should be ignored and pointer to its
-      // target otherwise.
-      //
-      // The same semantics as in file_rule below.
+      // target otherwise. The same semantics as in file_rule below.
       //
-      using alias_rule::filter; // "Unhide" to make Clang happy.
-
-      virtual const target*
+      virtual pair<const target*, uint64_t>
       filter (const scope*,
-              action, const target&,
-              const prerequisite&) const override;
+              action, const target&, const prerequisite&,
+              match_extra&) const override;
+
+      using alias_rule::filter; // "Unhide" to make Clang happy.
 
       virtual recipe
-      apply (action, target&) const override;
+      apply (action, target&, match_extra&) const override;
 
       group_rule (bool sto): see_through_only (sto) {}
       static const group_rule instance;
@@ -117,8 +133,21 @@ namespace build2
       virtual bool
       match (action, target&) const override;
 
+      // Return false if this ad hoc group member should be ignored and true
+      // otherwise. Note that this filter is called during execute and only
+      // for install/uninstall (and not update). For generality, it is also
+      // (first) called  on the target itself (can be detected by comparing
+      // the second and third arguments).
+      //
+      // The default implementation accepts all members.
+      //
+      virtual bool
+      filter (action, const target&, const target& adhoc_group_member) const;
+
       // Return NULL if this prerequisite should be ignored and pointer to its
-      // target otherwise.
+      // target otherwise. In the latter case, return the match options that
+      // should be used for this prerequisite (use match_extra::all_options
+      // and not 0 if no match options are needed).
       //
       // The default implementation ignores prerequsites that are outside of
       // the installation scope (see install_scope() for details). It also
@@ -130,27 +159,47 @@ namespace build2
       //
       // exe{foo}: exe{bar}: install = true # foo runs bar
       //
+      // The default implementation always returns match_extra::all_options.
+      // The match_extra argument is not used by the default implementation.
+      //
       // The prerequisite is passed as an iterator allowing the filter to
       // "see" inside groups.
       //
       using prerequisite_iterator =
         prerequisite_members_range<group_prerequisites>::iterator;
 
-      virtual const target*
+      virtual pair<const target*, uint64_t>
       filter (const scope*,
-              action, const target&, prerequisite_iterator&) const;
+              action, const target&, prerequisite_iterator&,
+              match_extra&) const;
 
-      virtual const target*
-      filter (const scope*, action, const target&, const prerequisite&) const;
+      virtual pair<const target*, uint64_t>
+      filter (const scope*,
+              action, const target&, const prerequisite&,
+              match_extra&) const;
 
+      // Note: rule::apply() override (with match_extra).
+      //
       virtual recipe
-      apply (action, target&) const override;
+      apply (action, target&, match_extra&) const override;
 
-      // Implementation of apply() that returns empty_recipe if the target is
-      // not installable.
+      // Implementation of apply() that returns empty_recipe (i.e., NULL) if
+      // the target is not installable.
+      //
+      // If the implementation may call reapply_impl(), then the reapply
+      // argument to apply_impl() must be true. Note that in this case, the
+      // *_impl() functions use the prerequisite_target::data member for own
+      // housekeeping.
       //
       recipe
-      apply_impl (action, target&) const;
+      apply_impl (action, target&, match_extra&, bool reapply = false) const;
+
+      // Implementation of reapply() that re-tries prerequisites that have
+      // been filtered out during the reapply() call. Note that currently not
+      // supported for update, only for install/uninstall.
+      //
+      void
+      reapply_impl (action, target&, match_extra&) const;
 
       static target_state
       perform_update (action, const target&);
@@ -288,6 +337,23 @@ namespace build2
 
       static const file_rule instance;
       file_rule () {}
+
+    private:
+      virtual recipe
+      apply (action, target&) const override; // Dummy simple_rule override.
+    };
+
+    class fsdir_rule: public simple_rule
+    {
+    public:
+      virtual bool
+      match (action, target&) const override;
+
+      virtual recipe
+      apply (action, target&) const override;
+
+      fsdir_rule () {}
+      static const fsdir_rule instance;
     };
   }
 }