Implement uninstall operation

13 files changed, 473 insertions, 161 deletions

diff --git a/build2/bin/init.cxx b/build2/bin/init.cxx
index 1d87fd2..424a729 100644
--- a/build2/bin/init.cxx
+++ b/build2/bin/init.cxx
@@ -399,6 +399,7 @@ namespace build2
         //   modules before all others?
         //
         r.insert<lib> (perform_install_id, "bin.lib", lib_);
+        r.insert<lib> (perform_uninstall_id, "bin.lib", lib_);
       }
 
       return true;
diff --git a/build2/c/init.cxx b/build2/c/init.cxx
index 7795181..52bf0b6 100644
--- a/build2/c/init.cxx
+++ b/build2/c/init.cxx
@@ -218,6 +218,7 @@ namespace build2
           "c.compile",
           "c.link",
           "c.install",
+          "c.uninstall",
 
           cast<string> (r[cm.x_id]),
           cast<string> (r[cm.x_target]),
diff --git a/build2/cc/common b/build2/cc/common
index 95f205a..2be290a 100644
--- a/build2/cc/common
+++ b/build2/cc/common
@@ -84,6 +84,7 @@ namespace build2
       const char* x_compile; // Rule names.
       const char* x_link;
       const char* x_install;
+      const char* x_uninstall;
 
       // Cached values for some commonly-used variables.
       //
@@ -122,6 +123,7 @@ namespace build2
             const char* compile,
             const char* link,
             const char* install,
+            const char* uninstall,
             const string& id,
             const string& tg,
             const string& sys,
@@ -130,7 +132,10 @@ namespace build2
             const target_type* const* hdr,
             const target_type* const* inc)
           : config_data (cd),
-            x_compile (compile), x_link (link), x_install (install),
+            x_compile (compile),
+            x_link (link),
+            x_install (install),
+            x_uninstall (uninstall),
             cid (id), ctg (tg), tsys (sys), tclass (class_),
             x_src (src), x_hdr (hdr), x_inc (inc) {}
     };
diff --git a/build2/cc/link.cxx b/build2/cc/link.cxx
index df1fa7e..61dd0ad 100644
--- a/build2/cc/link.cxx
+++ b/build2/cc/link.cxx
@@ -595,8 +595,12 @@ 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.
       //
+      auto op (a.operation ());
+      auto oop (a.outer_operation ());
+
       if (seen_lib && lt != otype::e &&
-          a.operation () != install_id && a.outer_operation () != install_id)
+          op != install_id   && oop != install_id &&
+          op != uninstall_id && oop != uninstall_id)
       {
         if (t.group != nullptr)
           t.group->prerequisite_targets.clear (); // lib{}'s
@@ -1087,6 +1091,8 @@ namespace build2
     {
       tracer trace (x, "link::perform_update");
 
+      auto oop (a.outer_operation ());
+
       file& t (static_cast<file&> (xt));
 
       scope& rs (t.root_scope ());
@@ -1107,7 +1113,7 @@ namespace build2
         // assembly itself is generated later, after updating the target. Omit
         // it if we are updating for install.
         //
-        if (a.outer_operation () != install_id)
+        if (oop != install_id && oop != uninstall_id)
           rpath_timestamp = windows_rpath_timestamp (t);
 
         path mf (
@@ -1354,7 +1360,7 @@ namespace build2
           {
             if (libs* ls = pt->is_a<libs> ())
             {
-              if (a.outer_operation () != install_id)
+              if (oop != install_id && oop != uninstall_id)
               {
                 sargs.push_back ("-Wl,-rpath," +
                                  ls->path ().directory ().string ());
@@ -1781,7 +1787,7 @@ namespace build2
       //
       if (lt == otype::e && tclass == "windows")
       {
-        if (a.outer_operation () != install_id)
+        if (oop != install_id && oop != uninstall_id)
           windows_rpath_assembly (t,
                                   cast<string> (rs[x_target_cpu]),
                                   rpath_timestamp,
diff --git a/build2/cc/module.cxx b/build2/cc/module.cxx
index ec7178b..d3849e1 100644
--- a/build2/cc/module.cxx
+++ b/build2/cc/module.cxx
@@ -307,30 +307,32 @@ namespace build2
         link&    lr (*this);
         install& ir (*this);
 
-        r.insert<obje> (perform_update_id,   x_compile, cr);
-        r.insert<obje> (perform_clean_id,    x_compile, cr);
-        r.insert<obje> (configure_update_id, x_compile, cr);
+        r.insert<obje> (perform_update_id,    x_compile, cr);
+        r.insert<obje> (perform_clean_id,     x_compile, cr);
+        r.insert<obje> (configure_update_id,  x_compile, cr);
 
-        r.insert<exe>  (perform_update_id,   x_link, lr);
-        r.insert<exe>  (perform_clean_id,    x_link, lr);
-        r.insert<exe>  (configure_update_id, x_link, lr);
+        r.insert<exe>  (perform_update_id,    x_link, lr);
+        r.insert<exe>  (perform_clean_id,     x_link, lr);
+        r.insert<exe>  (configure_update_id,  x_link, lr);
 
-        r.insert<exe>  (perform_install_id,  x_install, ir);
+        r.insert<exe>  (perform_install_id,   x_install, ir);
+        r.insert<exe>  (perform_uninstall_id, x_uninstall, ir);
 
         // Only register static object/library rules if the bin.ar module is
         // loaded (by us or by the user).
         //
         if (cast_false<bool> (b["bin.ar.loaded"]))
         {
-          r.insert<obja> (perform_update_id,   x_compile, cr);
-          r.insert<obja> (perform_clean_id,    x_compile, cr);
-          r.insert<obja> (configure_update_id, x_compile, cr);
+          r.insert<obja> (perform_update_id,    x_compile, cr);
+          r.insert<obja> (perform_clean_id,     x_compile, cr);
+          r.insert<obja> (configure_update_id,  x_compile, cr);
 
-          r.insert<liba> (perform_update_id,   x_link, lr);
-          r.insert<liba> (perform_clean_id,    x_link, lr);
-          r.insert<liba> (configure_update_id, x_link, lr);
+          r.insert<liba> (perform_update_id,    x_link, lr);
+          r.insert<liba> (perform_clean_id,     x_link, lr);
+          r.insert<liba> (configure_update_id,  x_link, lr);
 
-          r.insert<liba> (perform_install_id,  x_install, ir);
+          r.insert<liba> (perform_install_id,   x_install, ir);
+          r.insert<liba> (perform_uninstall_id, x_uninstall, ir);
         }
 
         r.insert<objs> (perform_update_id,   x_compile, cr);
@@ -341,7 +343,8 @@ namespace build2
         r.insert<libs> (perform_clean_id,    x_link, lr);
         r.insert<libs> (configure_update_id, x_link, lr);
 
-        r.insert<libs> (perform_install_id,  x_install, ir);
+        r.insert<libs> (perform_install_id,   x_install, ir);
+        r.insert<libs> (perform_uninstall_id, x_uninstall, ir);
       }
     }
   }
diff --git a/build2/context.cxx b/build2/context.cxx
index 670397f..422ecac 100644
--- a/build2/context.cxx
+++ b/build2/context.cxx
@@ -74,6 +74,7 @@ namespace build2
     operation_table.insert ("clean");
     operation_table.insert ("test");
     operation_table.insert ("install");
+    operation_table.insert ("uninstall");
 
     // Create global scope. For Win32 this is not a "real" root path.
     // On POSIX, however, this is a real path. See the comment in
diff --git a/build2/cxx/init.cxx b/build2/cxx/init.cxx
index 7170282..14134f1 100644
--- a/build2/cxx/init.cxx
+++ b/build2/cxx/init.cxx
@@ -225,6 +225,7 @@ namespace build2
           "cxx.compile",
           "cxx.link",
           "cxx.install",
+          "cxx.uninstall",
 
           cast<string> (r[cm.x_id]),
           cast<string> (r[cm.x_target]),
diff --git a/build2/install/init.cxx b/build2/install/init.cxx
index 06a3366..221cfcf 100644
--- a/build2/install/init.cxx
+++ b/build2/install/init.cxx
@@ -130,9 +130,10 @@ namespace build2
 
       l5 ([&]{trace << "for " << r.out_path ();});
 
-      // Register the install operation.
+      // Register the install and uninstall operations.
       //
       r.operations.insert (install_id, install);
+      r.operations.insert (uninstall_id, uninstall);
     }
 
     static const path cmd ("install");
@@ -186,10 +187,13 @@ namespace build2
         v.insert<string> ("install.mode");
       }
 
-      // Register our alias and file installer rule.
+      // Register our alias and file rules.
       //
-      b.rules.insert<alias> (perform_install_id, "install.alias", alias_);
-      b.rules.insert<file> (perform_install_id, "install.file", file_);
+      b.rules.insert<alias> (perform_install_id,   "install.alias", alias_);
+      b.rules.insert<alias> (perform_uninstall_id, "uninstall.alias", alias_);
+
+      b.rules.insert<file> (perform_install_id,   "install.file", file_);
+      b.rules.insert<file> (perform_uninstall_id, "uinstall.file", file_);
 
       // Configuration.
       //
diff --git a/build2/install/operation b/build2/install/operation
index 8c93627..9ae44cd 100644
--- a/build2/install/operation
+++ b/build2/install/operation
@@ -15,6 +15,7 @@ namespace build2
   namespace install
   {
     extern operation_info install;
+    extern operation_info uninstall;
   }
 }
 
diff --git a/build2/install/operation.cxx b/build2/install/operation.cxx
index 77deb2c..f08d85d 100644
--- a/build2/install/operation.cxx
+++ b/build2/install/operation.cxx
@@ -29,5 +29,25 @@ namespace build2
       &install_pre,
       nullptr
     };
+
+    // Note that we run update as a pre-operation, just like install. Which
+    // may seem bizarre at first. We do it to obtain the exact same dependency
+    // graph as install so that we uninstall exactly the same set of files as
+    // install would install. Note that just matching the rules without
+    // executing them may not be enough: for example, a presence of an ad hoc
+    // group member may only be discovered after executing the rule (e.g., VC
+    // link.exe only creates a DLL's import library if there are any exported
+    // symbols).
+    //
+    operation_info uninstall {
+      uninstall_id,
+      "uninstall",
+      "uninstall",
+      "uninstalling",
+      "is not installed",
+      execution_mode::last,
+      &install_pre,
+      nullptr
+    };
   }
 }
diff --git a/build2/install/rule b/build2/install/rule
index 9602190..99ebd8a 100644
--- a/build2/install/rule
+++ b/build2/install/rule
@@ -44,6 +44,9 @@ namespace build2
 
       static target_state
       perform_install (action, target&);
+
+      static target_state
+      perform_uninstall (action, target&);
     };
   }
 }
diff --git a/build2/install/rule.cxx b/build2/install/rule.cxx
index ac2fc8f..7365cae 100644
--- a/build2/install/rule.cxx
+++ b/build2/install/rule.cxx
@@ -78,7 +78,6 @@ namespace build2
 
     // file_rule
     //
-
     match_result file_rule::
     match (action a, target& t, const string&) const
     {
@@ -119,11 +118,11 @@ namespace build2
       //
       // 1. This target is installable.
       // 2. The action is either
-      //    a. (perform, install, 0) or
-      //    b. (*, update, install)
+      //    a. (perform, [un]install, 0) or
+      //    b. (*, update, [un]install)
       //
-      // In both cases, the next step is to search, match, and collect
-      // all the installable prerequisites.
+      // In both cases, the next step is to search, match, and collect all the
+      // installable prerequisites.
       //
       // @@ Perhaps if [noinstall] will be handled by the
       // group_prerequisite_members machinery, then we can just
@@ -147,7 +146,7 @@ namespace build2
         if (pt == nullptr)
           continue;
 
-        // See if were explicitly instructed not to install this target.
+        // See if we were explicitly instructed not to touch this target.
         //
         auto l ((*pt)["install"]);
         if (l && cast<dir_path> (l).string () == "false")
@@ -218,22 +217,127 @@ namespace build2
         };
       }
       else
-        return &perform_install;
+        return a.operation () == uninstall_id
+          ? &perform_uninstall
+          : &perform_install;
     }
 
     struct install_dir
     {
-      // @@ Why do we copy these? Why not just point to the values in vars?
-      //
-
       dir_path dir;
-      string sudo;
-      path cmd;
-      strings options;
-      string mode;
-      string dir_mode;
+
+      // If not NULL, then point to the corresponding install.* value.
+      //
+      const string* sudo      = nullptr;
+      const path*   cmd       = nullptr;
+      const strings* options  = nullptr;
+      const string*  mode     = nullptr;
+      const string*  dir_mode = nullptr;
+
+      explicit
+      install_dir (dir_path d = dir_path ()): dir (move (d)) {}
+
+      install_dir (dir_path d, const install_dir& b)
+          : dir (move (d)),
+            sudo (b.sudo),
+            cmd (b.cmd),
+            options (b.options),
+            mode (b.mode),
+            dir_mode (b.dir_mode) {}
     };
 
+    using install_dirs = vector<install_dir>;
+
+    // Resolve installation directory name to absolute directory path. Return
+    // all the super-directories leading up to the destination (last).
+    //
+    static install_dirs
+    resolve (target& t, dir_path d, const string* var = nullptr)
+    {
+      install_dirs rs;
+
+      if (d.absolute ())
+        rs.emplace_back (move (d.normalize ()));
+      else
+      {
+        // If it is relative, then the first component is treated as the
+        // installation directory name, e.g., bin, sbin, lib, etc. Look it
+        // up and recurse.
+        //
+        const string& sn (*d.begin ());
+        const string var ("install." + sn);
+        if (const dir_path* dn = lookup (t.base_scope (), var))
+        {
+          rs = resolve (t, *dn, &var);
+          d = rs.back ().dir / dir_path (++d.begin (), d.end ());
+          rs.emplace_back (move (d.normalize ()), rs.back ());
+        }
+        else
+          fail << "unknown installation directory name " << sn <<
+            info << "did you forget to specify config." << var << "?";
+      }
+
+      install_dir* r (&rs.back ());
+      scope& s (t.base_scope ());
+
+      // Override components in install_dir if we have our own.
+      //
+      if (var != nullptr)
+      {
+        if (auto l = s[*var + ".sudo"])     r->sudo     = &cast<string> (l);
+        if (auto l = s[*var + ".cmd"])      r->cmd      = &cast<path> (l);
+        if (auto l = s[*var + ".mode"])     r->mode     = &cast<string> (l);
+        if (auto l = s[*var + ".dir_mode"]) r->dir_mode = &cast<string> (l);
+        if (auto l = s[*var + ".options"])  r->options  = &cast<strings> (l);
+
+        if (auto l = s[*var + ".subdirs"])
+        {
+          if (cast<bool> (l))
+          {
+            // Find the scope from which this value came and use as a base
+            // to calculate the subdirectory.
+            //
+            for (const scope* p (&s); p != nullptr; p = p->parent_scope ())
+            {
+              if (l.belongs (*p)) // Ok since no target/type in lookup.
+              {
+                // The target can be in out or src.
+                //
+                const dir_path& d (
+                  (t.out.empty () ? t.dir : t.out).leaf (p->out_path ()));
+
+                // Add it as another leading directory rather than modifying
+                // the last one directly; somehow, it feels right.
+                //
+                rs.emplace_back (r->dir / d, rs.back ());
+                r = &rs.back ();
+                break;
+              }
+            }
+          }
+        }
+      }
+
+      // Set globals for unspecified components.
+      //
+      if (r->sudo == nullptr)
+        r->sudo = cast_null<string> (s["config.install.sudo"]);
+
+      if (r->cmd == nullptr)
+        r->cmd = &cast<path> (s["config.install.cmd"]);
+
+      if (r->options == nullptr)
+        r->options = cast_null<strings> (s["config.install.options"]);
+
+      if (r->mode == nullptr)
+        r->mode = &cast<string> (s["config.install.mode"]);
+
+      if (r->dir_mode == nullptr)
+        r->dir_mode = &cast<string> (s["config.install.dir_mode"]);
+
+      return rs;
+    }
+
     // On Windows we use MSYS2 install.exe and MSYS2 by default ignores
     // filesystem permissions (noacl mount option). And this means, for
     // example, that .exe that we install won't be runnable by Windows (MSYS2
@@ -260,9 +364,34 @@ namespace build2
 
     // install -d <dir>
     //
+    // If verbose is false, then only print the command at verbosity level 2
+    // or higher.
+    //
     static void
-    install (const install_dir& base, const dir_path& d)
+    install (const install_dir& base, const dir_path& d, bool verbose = true)
     {
+      try
+      {
+        if (dir_exists (d)) // May throw (e.g., EACCES).
+          return;
+      }
+      catch (const system_error& e)
+      {
+        fail << "invalid installation directory " << d << ": " << e.what ();
+      }
+
+      // While install -d will create all the intermediate components between
+      // base and dir, we do it explicitly, one at a time. This way the output
+      // is symmetrical to uninstall() below.
+      //
+      if (d != base.dir)
+      {
+        dir_path pd (d.directory ());
+
+        if (pd != base.dir)
+          install (base, pd, verbose);
+      }
+
       cstrings args;
 
       dir_path reld (
@@ -270,23 +399,23 @@ namespace build2
         ? msys_path (d)
         : relative (d));
 
-      if (!base.sudo.empty ())
-        args.push_back (base.sudo.c_str ());
+      if (base.sudo != nullptr)
+        args.push_back (base.sudo->c_str ());
 
-      args.push_back (base.cmd.string ().c_str ());
+      args.push_back (base.cmd->string ().c_str ());
       args.push_back ("-d");
 
-      if (!base.options.empty ())
-        append_options (args, base.options);
+      if (base.options != nullptr)
+        append_options (args, *base.options);
 
       args.push_back ("-m");
-      args.push_back (base.dir_mode.c_str ());
+      args.push_back (base.dir_mode->c_str ());
       args.push_back (reld.string ().c_str ());
       args.push_back (nullptr);
 
       if (verb >= 2)
         print_process (args);
-      else if (verb)
+      else if (verb && verbose)
         text << "install " << d;
 
       try
@@ -324,16 +453,16 @@ namespace build2
 
       cstrings args;
 
-      if (!base.sudo.empty ())
-        args.push_back (base.sudo.c_str ());
+      if (base.sudo != nullptr)
+        args.push_back (base.sudo->c_str ());
 
-      args.push_back (base.cmd.string ().c_str ());
+      args.push_back (base.cmd->string ().c_str ());
 
-      if (!base.options.empty ())
-        append_options (args, base.options);
+      if (base.options != nullptr)
+        append_options (args, *base.options);
 
       args.push_back ("-m");
-      args.push_back (base.mode.c_str ());
+      args.push_back (base.mode->c_str ());
       args.push_back (relf.string ().c_str ());
       args.push_back (reld.string ().c_str ());
       args.push_back (nullptr);
@@ -361,152 +490,287 @@ namespace build2
       }
     }
 
-    // Resolve installation directory name to absolute directory path,
-    // creating leading directories as necessary.
-    //
-    static install_dir
-    resolve (target& t, dir_path d, const string* var = nullptr)
+    target_state file_rule::
+    perform_install (action a, target& xt)
     {
-      install_dir r;
+      file& t (static_cast<file&> (xt));
+      assert (!t.path ().empty ()); // Should have been assigned by update.
+
+      auto install_target = [](file& t, const dir_path& d, bool verbose)
+      {
+        // Resolve target directory.
+        //
+        install_dirs ids (resolve (t, d));
+
+        // Create leading directories. Note that we are using the leading
+        // directory (if there is one) for the creation information (mode,
+        // sudo, etc).
+        //
+        for (auto i (ids.begin ()), j (i); i != ids.end (); j = i++)
+          install (*j, i->dir, verbose); // install -d
+
+        install_dir& id (ids.back ());
+
+        // Override mode if one was specified.
+        //
+        if (auto l = t["install.mode"])
+          id.mode = &cast<string> (l);
+
+        install (id, t, verbose);
+      };
+
+      // First handle installable prerequisites.
+      //
+      target_state r (execute_prerequisites (a, t));
+
+      // Then installable ad hoc group members, if any.
+      //
+      for (target* m (t.member); m != nullptr; m = m->member)
+      {
+        if (const dir_path* d = lookup (*m, "install"))
+          install_target (static_cast<file&> (*m), *d, false);
+      }
+
+      // Finally install the target itself (since we got here we know the
+      // install variable is there).
+      //
+      install_target (t, cast<dir_path> (t["install"]), true);
+
+      return (r |= target_state::changed);
+    }
 
+    // uninstall -d <dir>
+    //
+    // We try remove all the directories between base and dir but not base
+    // itself unless base == dir. Return false if nothing has been removed
+    // (i.e., the directories do not exist or are not empty).
+    //
+    // If verbose is false, then only print the command at verbosity level 2
+    // or higher.
+    //
+    static bool
+    uninstall (const install_dir& base, const dir_path& d, bool verbose = true)
+    {
+      // Figure out if we should try to remove this directory. Note that if
+      // it doesn't exist, then we may still need to remove outer ones.
+      //
+      bool r (false);
       try
       {
-        if (d.absolute ())
-          r.dir = move (d.normalize ());
-        else
+        if ((r = dir_exists (d))) // May throw (e.g., EACCES).
         {
-          // If it is relative, then the first component is treated
-          // as the installation directory name, e.g., bin, sbin, lib,
-          // etc. Look it up and recurse.
-          //
-          const string& sn (*d.begin ());
-          const string var ("install." + sn);
-          if (const dir_path* dn = lookup (t.base_scope (), var))
-          {
-            r = resolve (t, *dn, &var);
-            d = r.dir / dir_path (++d.begin (), d.end ());
-            r.dir = move (d.normalize ());
-
-            if (!dir_exists (r.dir)) // May throw (e.g., EACCES).
-              install (r, r.dir); // install -d
-          }
-          else
-            fail << "unknown installation directory name " << sn <<
-              info << "did you forget to specify config." << var << "?";
+          if (!dir_empty (d)) // May also throw.
+            return false; // Won't be able to remove any outer directories.
         }
+      }
+      catch (const system_error& e)
+      {
+        fail << "invalid installation directory " << d << ": " << e.what ();
+      }
 
-        scope& s (t.base_scope ());
+      if (r)
+      {
+        dir_path reld (relative (d));
 
-        // Override components in install_dir if we have our own.
+        // Normally when we need to remove a file or directory we do it
+        // directly without calling rm/rmdir. This however, won't work if we
+        // have sudo. So we are going to do it both ways. Thankfully, no sudo
+        // on Windows.
         //
-        if (var != nullptr)
+        if (base.sudo == nullptr)
         {
-          if (auto l = s[*var + ".sudo"])     r.sudo = cast<string> (l);
-          if (auto l = s[*var + ".cmd"])      r.cmd = cast<path> (l);
-          if (auto l = s[*var + ".mode"])     r.mode = cast<string> (l);
-          if (auto l = s[*var + ".dir_mode"]) r.dir_mode = cast<string> (l);
-          if (auto l = s[*var + ".options"])  r.options = cast<strings> (l);
+          if (verb >= 2)
+            text << "rmdir " << reld;
+          else if (verb && verbose)
+            text << "uninstall " << reld;
 
-          if (auto l = s[*var + ".subdirs"])
+          try
           {
-            if (cast<bool> (l))
-            {
-              // Find the scope from which this value came and use as a base
-              // to calculate the subdirectory.
-              //
-              for (const scope* p (&s); p != nullptr; p = p->parent_scope ())
-              {
-                if (l.belongs (*p)) // Ok since no target/type in lookup.
-                {
-                  // The target can be in out or src.
-                  //
-                  r.dir /= (t.out.empty () ? t.dir : t.out).leaf (
-                    p->out_path ());
-                  break;
-                }
-              }
-            }
+            try_rmdir (d);
+          }
+          catch (const system_error& e)
+          {
+            fail << "unable to remove directory " << d << ": " << e.what ();
           }
         }
+        else
+        {
+          cstrings args {base.sudo->c_str (),
+                         "rmdir",
+                         reld.string ().c_str (),
+                         nullptr};
 
-        // Set globals for unspecified components.
-        //
-        if (r.sudo.empty ())
-          if (auto l = s["config.install.sudo"])
-            r.sudo = cast<string> (l);
+          if (verb >= 2)
+            print_process (args);
+          else if (verb && verbose)
+            text << "uninstall " << reld;
 
-        if (r.cmd.empty ())
-          r.cmd = cast<path> (s["config.install.cmd"]);
+          try
+          {
+            process pr (args.data ());
 
-        if (r.options.empty ())
-          if (auto l = s["config.install.options"])
-            r.options = cast<strings> (l);
+            if (!pr.wait ())
+              throw failed ();
+          }
+          catch (const process_error& e)
+          {
+            error << "unable to execute " << args[0] << ": " << e.what ();
 
-        if (r.mode.empty ())
-          r.mode = cast<string> (s["config.install.mode"]);
+            if (e.child ())
+              exit (1);
 
-        if (r.dir_mode.empty ())
-          r.dir_mode = cast<string> (s["config.install.dir_mode"]);
+            throw failed ();
+          }
+        }
+      }
 
-        // If the directory still doesn't exist, then this means it was
-        // specified as absolute (it will normally be install.root with
-        // everything else defined in term of it). We used to fail in this
-        // case but that proved to be just too anal. So now we create it.
-        //
-        // Also, with the .subdirs logic we may end up with a non-existent
-        // subdirectory.
-        //
-        if (!dir_exists (r.dir)) // May throw (e.g., EACCES).
-          // fail << "installation directory " << d << " does not exist";
-          install (r, r.dir); // install -d
+      // If we have more empty directories between base and dir, then try
+      // to clean them up as well.
+      //
+      if (d != base.dir)
+      {
+        dir_path pd (d.directory ());
+
+        if (pd != base.dir)
+          r = uninstall (base, pd, verbose) || r;
+      }
+
+      return r;
+    }
+
+    // uninstall <file> <dir>
+    //
+    // Return false if nothing has been removed (i.e., the file does not
+    // exist).
+    //
+    // If verbose is false, then only print the command at verbosity level 2
+    // or higher.
+    //
+    static bool
+    uninstall (const install_dir& base, file& t, bool verbose = true)
+    {
+      path f (base.dir / t.path ().leaf ());
+
+      try
+      {
+        if (!file_exists (f)) // May throw (e.g., EACCES).
+          return false;
       }
       catch (const system_error& e)
       {
-        fail << "invalid installation directory " << r.dir << ": "
-             << e.what ();
+        fail << "invalid installation path " << f << ": " << e.what ();
       }
 
-      return r;
+      path relf (relative (f));
+
+      // The same story as with uninstall -d.
+      //
+      if (base.sudo == nullptr)
+      {
+        if (verb >= 2)
+          text << "rm " << relf;
+        else if (verb && verbose)
+          text << "uninstall " << t;
+
+        try
+        {
+          try_rmfile (f);
+        }
+        catch (const system_error& e)
+        {
+          fail << "unable to remove file " << f << ": " << e.what ();
+        }
+      }
+      else
+      {
+        cstrings args {base.sudo->c_str (),
+                       "rm",
+                       "-f",
+                       relf.string ().c_str (),
+                       nullptr};
+
+        if (verb >= 2)
+          print_process (args);
+        else if (verb && verbose)
+          text << "uninstall " << t;
+
+        try
+        {
+          process pr (args.data ());
+
+          if (!pr.wait ())
+            throw failed ();
+        }
+        catch (const process_error& e)
+        {
+          error << "unable to execute " << args[0] << ": " << e.what ();
+
+          if (e.child ())
+            exit (1);
+
+          throw failed ();
+        }
+      }
+
+      return true;
     }
 
     target_state file_rule::
-    perform_install (action a, target& xt)
+    perform_uninstall (action a, target& xt)
     {
       file& t (static_cast<file&> (xt));
       assert (!t.path ().empty ()); // Should have been assigned by update.
 
-      auto install_target = [](file& t, const dir_path& d, bool verbose)
+      auto uninstall_target = [](file& t, const dir_path& d, bool verbose)
+        -> target_state
       {
-        // Resolve and, if necessary, create target directory.
+        // Resolve target directory.
         //
-        install_dir id (resolve (t, d));
+        install_dirs ids (resolve (t, d));
 
-        // Override mode if one was specified.
+        // Remove the target itself.
         //
-        if (auto l = t["install.mode"])
-          id.mode = cast<string> (l);
+        target_state r (uninstall (ids.back (), t, verbose)
+                        ? target_state::changed
+                        : target_state::unchanged);
 
-        install (id, t, verbose);
+        // Clean up empty leading directories (in reverse).
+        //
+        // Note that we are using the leading directory (if there is one)
+        // for the clean up information (sudo, etc).
+        //
+        for (auto i (ids.rbegin ()), j (i), e (ids.rend ()); i != e; j = ++i)
+        {
+          if (uninstall (++j != e ? *j : *i, i->dir, verbose))
+            r |= target_state::changed;
+        }
+
+        return r;
       };
 
-      // First handle installable prerequisites.
+      // Reverse order of installation: first the target itself (since we got
+      // here we know the install variable is there).
       //
-      target_state r (execute_prerequisites (a, t));
+      target_state r (
+        uninstall_target (t, cast<dir_path> (t["install"]), true));
 
-      // Then installable ad hoc group members, if any.
+      // Then installable ad hoc group members, if any. To be anally precise
+      // we would have to do it in reverse, but that's not easy (it's a
+      // single-linked list).
       //
       for (target* m (t.member); m != nullptr; m = m->member)
       {
         if (const dir_path* d = lookup (*m, "install"))
-          install_target (static_cast<file&> (*m), *d, false);
+          r |= uninstall_target (static_cast<file&> (*m),
+                                 *d,
+                                 r != target_state::changed);
       }
 
-      // Finally install the target itself (since we got here we know the
-      // install variable is there).
+      // Finally handle installable prerequisites.
       //
-      install_target (t, cast<dir_path> (t["install"]), true);
+      r |= reverse_execute_prerequisites (a, t);
 
-      return (r |= target_state::changed);
+      return r;
     }
   }
 }
diff --git a/build2/operation b/build2/operation
index 152353b..730a958 100644
--- a/build2/operation
+++ b/build2/operation
@@ -108,16 +108,18 @@ namespace build2
   // that no operation was explicitly specified by the user. If adding
   // something here remember to update the man page.
   //
-  const operation_id default_id = 1; // Shall be first.
-  const operation_id update_id = 2;
-  const operation_id clean_id  = 3;
-  const operation_id test_id = 4;
-  const operation_id install_id = 5;
-
-  const action_id perform_update_id   = (perform_id << 4) | update_id;
-  const action_id perform_clean_id    = (perform_id << 4) | clean_id;
-  const action_id perform_test_id     = (perform_id << 4) | test_id;
-  const action_id perform_install_id  = (perform_id << 4) | install_id;
+  const operation_id default_id   = 1; // Shall be first.
+  const operation_id update_id    = 2;
+  const operation_id clean_id     = 3;
+  const operation_id test_id      = 4;
+  const operation_id install_id   = 5;
+  const operation_id uninstall_id = 6;
+
+  const action_id perform_update_id     = (perform_id << 4) | update_id;
+  const action_id perform_clean_id      = (perform_id << 4) | clean_id;
+  const action_id perform_test_id       = (perform_id << 4) | test_id;
+  const action_id perform_install_id    = (perform_id << 4) | install_id;
+  const action_id perform_uninstall_id  = (perform_id << 4) | uninstall_id;
 
   const action_id configure_update_id   = (configure_id << 4) | update_id;
 
@@ -140,7 +142,7 @@ namespace build2
   // If we use the last/back mode for, say, clean, then we will remove
   // targets in the order inverse to the way they were updated. While
   // this sounds like an elegant idea, are there any practical benefits
-  // of doing it this way. As it turns out there is (at least) one: when
+  // of doing it this way? As it turns out there is (at least) one: when
   // we are removing a directory (see fsdir{}), we want to do it after
   // all the targets that depend on it (such as files, sub-directories)
   // were removed. If we do it before, then the directory won't be empty