Split build system into library and driver

1 files changed, 1026 insertions, 0 deletions

diff --git a/libbuild2/context.cxx b/libbuild2/context.cxx
new file mode 100644
index 0000000..d56abb3
--- /dev/null
+++ b/libbuild2/context.cxx
@@ -0,0 +1,1026 @@
+// file      : libbuild2/context.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <libbuild2/context.hxx>
+
+#include <sstream>
+#include <exception> // uncaught_exception[s]()
+
+#include <libbuild2/rule.hxx>
+#include <libbuild2/scope.hxx>
+#include <libbuild2/target.hxx>
+#include <libbuild2/diagnostics.hxx>
+
+#include <libbutl/ft/exception.hxx> // uncaught_exceptions
+
+// For command line variable parsing.
+//
+#include <libbuild2/token.hxx>
+#include <libbuild2/lexer.hxx>
+#include <libbuild2/parser.hxx>
+
+using namespace std;
+using namespace butl;
+
+namespace build2
+{
+  scheduler sched;
+
+  run_phase phase;
+  phase_mutex phase_mutex::instance;
+
+  size_t load_generation;
+
+  bool phase_mutex::
+  lock (run_phase p)
+  {
+    bool r;
+
+    {
+      mlock l (m_);
+      bool u (lc_ == 0 && mc_ == 0 && ec_ == 0); // Unlocked.
+
+      // Increment the counter.
+      //
+      condition_variable* v (nullptr);
+      switch (p)
+      {
+      case run_phase::load:    lc_++; v = &lv_; break;
+      case run_phase::match:   mc_++; v = &mv_; break;
+      case run_phase::execute: ec_++; v = &ev_; break;
+      }
+
+      // If unlocked, switch directly to the new phase. Otherwise wait for the
+      // phase switch. Note that in the unlocked case we don't need to notify
+      // since there is nobody waiting (all counters are zero).
+      //
+      if (u)
+      {
+        phase = p;
+        r = !fail_;
+      }
+      else if (phase != p)
+      {
+        sched.deactivate ();
+        for (; phase != p; v->wait (l)) ;
+        r = !fail_;
+        l.unlock (); // Important: activate() can block.
+        sched.activate ();
+      }
+      else
+        r = !fail_;
+    }
+
+    // In case of load, acquire the exclusive access mutex.
+    //
+    if (p == run_phase::load)
+    {
+      lm_.lock ();
+      r = !fail_; // Re-query.
+    }
+
+    return r;
+  }
+
+  void phase_mutex::
+  unlock (run_phase p)
+  {
+    // In case of load, release the exclusive access mutex.
+    //
+    if (p == run_phase::load)
+      lm_.unlock ();
+
+    {
+      mlock l (m_);
+
+      // Decrement the counter and see if this phase has become unlocked.
+      //
+      bool u (false);
+      switch (p)
+      {
+      case run_phase::load:    u = (--lc_ == 0); break;
+      case run_phase::match:   u = (--mc_ == 0); break;
+      case run_phase::execute: u = (--ec_ == 0); break;
+      }
+
+      // If the phase is unlocked, pick a new phase and notify the waiters.
+      // Note that we notify all load waiters so that they can all serialize
+      // behind the second-level mutex.
+      //
+      if (u)
+      {
+        condition_variable* v;
+
+        if      (lc_ != 0) {phase = run_phase::load;    v = &lv_;}
+        else if (mc_ != 0) {phase = run_phase::match;   v = &mv_;}
+        else if (ec_ != 0) {phase = run_phase::execute; v = &ev_;}
+        else               {phase = run_phase::load;    v = nullptr;}
+
+        if (v != nullptr)
+        {
+          l.unlock ();
+          v->notify_all ();
+        }
+      }
+    }
+  }
+
+  bool phase_mutex::
+  relock (run_phase o, run_phase n)
+  {
+    // Pretty much a fused unlock/lock implementation except that we always
+    // switch into the new phase.
+    //
+    assert (o != n);
+
+    bool r;
+
+    if (o == run_phase::load)
+      lm_.unlock ();
+
+    {
+      mlock l (m_);
+      bool u (false);
+
+      switch (o)
+      {
+      case run_phase::load:    u = (--lc_ == 0); break;
+      case run_phase::match:   u = (--mc_ == 0); break;
+      case run_phase::execute: u = (--ec_ == 0); break;
+      }
+
+      // Set if will be waiting or notifying others.
+      //
+      condition_variable* v (nullptr);
+      switch (n)
+      {
+      case run_phase::load:    v = lc_++ != 0 || !u ? &lv_ : nullptr; break;
+      case run_phase::match:   v = mc_++ != 0 || !u ? &mv_ : nullptr; break;
+      case run_phase::execute: v = ec_++ != 0 || !u ? &ev_ : nullptr; break;
+      }
+
+      if (u)
+      {
+        phase = n;
+        r = !fail_;
+
+        // Notify others that could be waiting for this phase.
+        //
+        if (v != nullptr)
+        {
+          l.unlock ();
+          v->notify_all ();
+        }
+      }
+      else // phase != n
+      {
+        sched.deactivate ();
+        for (; phase != n; v->wait (l)) ;
+        r = !fail_;
+        l.unlock (); // Important: activate() can block.
+        sched.activate ();
+      }
+    }
+
+    if (n == run_phase::load)
+    {
+      lm_.lock ();
+      r = !fail_; // Re-query.
+    }
+
+    return r;
+  }
+
+  // C++17 deprecated uncaught_exception() so use uncaught_exceptions() if
+  // available.
+  //
+  static inline bool
+  uncaught_exception ()
+  {
+#ifdef __cpp_lib_uncaught_exceptions
+    return std::uncaught_exceptions () != 0;
+#else
+    return std::uncaught_exception ();
+#endif
+  }
+
+  // phase_lock
+  //
+  static
+#ifdef __cpp_thread_local
+  thread_local
+#else
+  __thread
+#endif
+  phase_lock* phase_lock_instance;
+
+  phase_lock::
+  phase_lock (run_phase p)
+      : p (p)
+  {
+    if (phase_lock* l = phase_lock_instance)
+      assert (l->p == p);
+    else
+    {
+      if (!phase_mutex::instance.lock (p))
+      {
+        phase_mutex::instance.unlock (p);
+        throw failed ();
+      }
+
+      phase_lock_instance = this;
+
+      //text << this_thread::get_id () << " phase acquire " << p;
+    }
+  }
+
+  phase_lock::
+  ~phase_lock ()
+  {
+    if (phase_lock_instance == this)
+    {
+      phase_lock_instance = nullptr;
+      phase_mutex::instance.unlock (p);
+
+      //text << this_thread::get_id () << " phase release " << p;
+    }
+  }
+
+  // phase_unlock
+  //
+  phase_unlock::
+  phase_unlock (bool u)
+      : l (u ? phase_lock_instance : nullptr)
+  {
+    if (u)
+    {
+      phase_lock_instance = nullptr;
+      phase_mutex::instance.unlock (l->p);
+
+      //text << this_thread::get_id () << " phase unlock  " << l->p;
+    }
+  }
+
+  phase_unlock::
+  ~phase_unlock () noexcept (false)
+  {
+    if (l != nullptr)
+    {
+      bool r (phase_mutex::instance.lock (l->p));
+      phase_lock_instance = l;
+
+      // Fail unless we are already failing. Note that we keep the phase
+      // locked since there will be phase_lock down the stack to unlock it.
+      //
+      if (!r && !uncaught_exception ())
+        throw failed ();
+
+      //text << this_thread::get_id () << " phase lock    " << l->p;
+    }
+  }
+
+  // phase_switch
+  //
+  phase_switch::
+  phase_switch (run_phase n)
+      : o (phase), n (n)
+  {
+    if (!phase_mutex::instance.relock (o, n))
+    {
+      phase_mutex::instance.relock (n, o);
+      throw failed ();
+    }
+
+    phase_lock_instance->p = n;
+
+    if (n == run_phase::load) // Note: load lock is exclusive.
+      load_generation++;
+
+    //text << this_thread::get_id () << " phase switch  " << o << " " << n;
+  }
+
+  phase_switch::
+  ~phase_switch () noexcept (false)
+  {
+    // If we are coming off a failed load phase, mark the phase_mutex as
+    // failed to terminate all other threads since the build state may no
+    // longer be valid.
+    //
+    if (n == run_phase::load && uncaught_exception ())
+    {
+      mlock l (phase_mutex::instance.m_);
+      phase_mutex::instance.fail_ = true;
+    }
+
+    bool r (phase_mutex::instance.relock (n, o));
+    phase_lock_instance->p = o;
+
+    // Similar logic to ~phase_unlock().
+    //
+    if (!r && !uncaught_exception ())
+      throw failed ();
+
+    //text << this_thread::get_id () << " phase restore " << n << " " << o;
+  }
+
+  const variable* var_src_root;
+  const variable* var_out_root;
+  const variable* var_src_base;
+  const variable* var_out_base;
+  const variable* var_forwarded;
+
+  const variable* var_project;
+  const variable* var_amalgamation;
+  const variable* var_subprojects;
+  const variable* var_version;
+
+  const variable* var_project_url;
+  const variable* var_project_summary;
+
+  const variable* var_import_target;
+
+  const variable* var_clean;
+  const variable* var_backlink;
+  const variable* var_include;
+
+  const char var_extension[10] = "extension";
+
+  const variable* var_build_meta_operation;
+
+  string current_mname;
+  string current_oname;
+
+  const meta_operation_info* current_mif;
+  const operation_info* current_inner_oif;
+  const operation_info* current_outer_oif;
+  size_t current_on;
+  execution_mode current_mode;
+  bool current_diag_noise;
+
+  atomic_count dependency_count;
+  atomic_count target_count;
+  atomic_count skip_count;
+
+  bool keep_going = false;
+  bool dry_run = false;
+
+  void (*config_save_variable) (scope&, const variable&, uint64_t);
+
+  const string& (*config_preprocess_create) (const variable_overrides&,
+                                             values&,
+                                             vector_view<opspec>&,
+                                             bool,
+                                             const location&);
+
+  variable_overrides
+  reset (const strings& cmd_vars)
+  {
+    tracer trace ("reset");
+
+    // @@ Need to unload modules when we dynamically load them.
+    //
+
+    l6 ([&]{trace << "resetting build state";});
+
+    auto& vp (variable_pool::instance);
+    auto& sm (scope_map::instance);
+
+    variable_overrides vos;
+
+    targets.clear ();
+    sm.clear ();
+    vp.clear ();
+
+    // Reset meta/operation tables. Note that the order should match the id
+    // constants in <libbuild2/operation.hxx>.
+    //
+    meta_operation_table.clear ();
+    meta_operation_table.insert ("noop");
+    meta_operation_table.insert ("perform");
+    meta_operation_table.insert ("configure");
+    meta_operation_table.insert ("disfigure");
+
+    if (config_preprocess_create != nullptr)
+      meta_operation_table.insert (
+        meta_operation_data ("create", config_preprocess_create));
+
+    meta_operation_table.insert ("dist");
+    meta_operation_table.insert ("info");
+
+    operation_table.clear ();
+    operation_table.insert ("default");
+    operation_table.insert ("update");
+    operation_table.insert ("clean");
+    operation_table.insert ("test");
+    operation_table.insert ("update-for-test");
+    operation_table.insert ("install");
+    operation_table.insert ("uninstall");
+    operation_table.insert ("update-for-install");
+
+    // Create global scope. Note that the empty path is a prefix for any other
+    // path. See the comment in <libbutl/prefix-map.mxx> for details.
+    //
+    auto make_global_scope = [] () -> scope&
+    {
+      auto i (scope_map::instance.insert (dir_path ()));
+      scope& r (i->second);
+      r.out_path_ = &i->first;
+      global_scope = scope::global_ = &r;
+      return r;
+    };
+
+    scope& gs (make_global_scope ());
+
+    // Setup the global scope before parsing any variable overrides since they
+    // may reference these things.
+    //
+
+    gs.assign<dir_path> ("build.work") = work;
+    gs.assign<dir_path> ("build.home") = home;
+
+    // Build system driver process path.
+    //
+    gs.assign<process_path> ("build.path") =
+      process_path (nullptr, // Will be filled by value assignment.
+                    path (argv0.recall_string ()),
+                    path (argv0.effect));
+
+    // Build system verbosity level.
+    //
+    gs.assign<uint64_t> ("build.verbosity") = verb;
+
+    // Build system version (similar to what we do in the version module
+    // except here we don't include package epoch/revision).
+    //
+    {
+      const standard_version& v (build_version);
+
+      auto set = [&gs] (const char* var, auto val)
+      {
+        using T = decltype (val);
+        gs.assign (variable_pool::instance.insert<T> (var)) = move (val);
+      };
+
+      set ("build.version", v.string_project ());
+
+      set ("build.version.number", v.version);
+      set ("build.version.id",     v.string_project_id ());
+
+      set ("build.version.major", uint64_t (v.major ()));
+      set ("build.version.minor", uint64_t (v.minor ()));
+      set ("build.version.patch", uint64_t (v.patch ()));
+
+      optional<uint16_t> a (v.alpha ());
+      optional<uint16_t> b (v.beta ());
+
+      set ("build.version.alpha",              a.has_value ());
+      set ("build.version.beta",               b.has_value ());
+      set ("build.version.pre_release",        v.pre_release ().has_value ());
+      set ("build.version.pre_release_string", v.string_pre_release ());
+      set ("build.version.pre_release_number", uint64_t (a ? *a : b ? *b : 0));
+
+      set ("build.version.snapshot",        v.snapshot ()); // bool
+      set ("build.version.snapshot_sn",     v.snapshot_sn); // uint64
+      set ("build.version.snapshot_id",     v.snapshot_id); // string
+      set ("build.version.snapshot_string", v.string_snapshot ());
+
+      // Allow detection (for example, in tests) whether this is a staged
+      // toolchain.
+      //
+      // Note that it is either staged or public, without queued, since we do
+      // not re-package things during the queued-to-public transition.
+      //
+      set ("build.version.stage", LIBBUILD2_STAGE);
+    }
+
+    // Enter the host information. Rather than jumping through hoops like
+    // config.guess, for now we are just going to use the compiler target we
+    // were built with. While it is not as precise (for example, a binary
+    // built for i686 might be running on x86_64), it is good enough of an
+    // approximation/fallback since most of the time we are interested in just
+    // the target class (e.g., linux, windows, macosx).
+    //
+    {
+      // Did the user ask us to use config.guess?
+      //
+      string orig (config_guess
+                   ? run<string> (3,
+                                  *config_guess,
+                                  [](string& l, bool) {return move (l);})
+                   : BUILD2_HOST_TRIPLET);
+
+      l5 ([&]{trace << "original host: '" << orig << "'";});
+
+      try
+      {
+        target_triplet t (orig);
+
+        l5 ([&]{trace << "canonical host: '" << t.string () << "'; "
+                      << "class: " << t.class_;});
+
+        // Also enter as build.host.{cpu,vendor,system,version,class} for
+        // convenience of access.
+        //
+        gs.assign<string> ("build.host.cpu")     = t.cpu;
+        gs.assign<string> ("build.host.vendor")  = t.vendor;
+        gs.assign<string> ("build.host.system")  = t.system;
+        gs.assign<string> ("build.host.version") = t.version;
+        gs.assign<string> ("build.host.class")   = t.class_;
+
+        gs.assign<target_triplet> ("build.host") = move (t);
+      }
+      catch (const invalid_argument& e)
+      {
+        fail << "unable to parse build host '" << orig << "': " << e <<
+          info << "consider using the --config-guess option";
+      }
+    }
+
+    // Register builtin target types.
+    //
+    {
+      target_type_map& t (gs.target_types);
+
+      t.insert<file>  ();
+      t.insert<alias> ();
+      t.insert<dir>   ();
+      t.insert<fsdir> ();
+      t.insert<exe>   ();
+      t.insert<doc>   ();
+      t.insert<man>   ();
+      t.insert<man1>  ();
+
+      {
+        auto& tt (t.insert<manifest> ());
+        t.insert_file ("manifest", tt);
+      }
+
+      {
+        auto& tt (t.insert<buildfile> ());
+        t.insert_file ("buildfile", tt);
+      }
+    }
+
+    // Parse and enter the command line variables. We do it before entering
+    // any other variables so that all the variables that are overriden are
+    // marked as such first. Then, as we enter variables, we can verify that
+    // the override is alowed.
+    //
+    for (size_t i (0); i != cmd_vars.size (); ++i)
+    {
+      const string& s (cmd_vars[i]);
+
+      istringstream is (s);
+      is.exceptions (istringstream::failbit | istringstream::badbit);
+
+      // Similar to buildspec we do "effective escaping" and only for ['"\$(]
+      // (basically what's necessary inside a double-quoted literal plus the
+      // single quote).
+      //
+      lexer l (is, path ("<cmdline>"), 1 /* line */, "\'\"\\$(");
+
+      // At the buildfile level the scope-specific variable should be
+      // separated from the directory with a whitespace, for example:
+      //
+      // ./ foo=$bar
+      //
+      // However, requiring this for command line variables would be too
+      // inconvinient so we support both.
+      //
+      // We also have the optional visibility modifier as a first character of
+      // the variable name:
+      //
+      // ! - global
+      // % - project
+      // / - scope
+      //
+      // The last one clashes a bit with the directory prefix:
+      //
+      // ./ /foo=bar
+      // .//foo=bar
+      //
+      // But that's probably ok (the need for a scope-qualified override with
+      // scope visibility should be pretty rare). Note also that to set the
+      // value on the global scope we use !.
+      //
+      // And so the first token should be a word which can be either a
+      // variable name (potentially with the directory qualification) or just
+      // the directory, in which case it should be followed by another word
+      // (unqualified variable name).
+      //
+      token t (l.next ());
+
+      optional<dir_path> dir;
+      if (t.type == token_type::word)
+      {
+        string& v (t.value);
+        size_t p (path::traits_type::rfind_separator (v));
+
+        if (p != string::npos && p != 0) // If first then visibility.
+        {
+          if (p == v.size () - 1)
+          {
+            // Separate directory.
+            //
+            dir = dir_path (move (v));
+            t = l.next ();
+
+            // Target-specific overrides are not yet supported (and probably
+            // never will be; the beast is already complex enough).
+            //
+            if (t.type == token_type::colon)
+              fail << "'" << s << "' is a target-specific override" <<
+                info << "use double '--' to treat this argument as buildspec";
+          }
+          else
+          {
+            // Combined directory.
+            //
+            // If double separator (visibility marker), then keep the first in
+            // name.
+            //
+            if (p != 0 && path::traits_type::is_separator (v[p - 1]))
+              --p;
+
+            dir = dir_path (t.value, 0, p + 1); // Include the separator.
+            t.value.erase (0, p + 1);           // Erase the separator.
+          }
+
+          if (dir->relative ())
+          {
+            // Handle the special relative to base scope case (.../).
+            //
+            auto i (dir->begin ());
+
+            if (*i == "...")
+              dir = dir_path (++i, dir->end ()); // Note: can become empty.
+            else
+              dir->complete (); // Relative to CWD.
+          }
+
+          if (dir->absolute ())
+            dir->normalize ();
+        }
+      }
+
+      token_type tt (l.next ().type);
+
+      // The token should be the variable name followed by =, +=, or =+.
+      //
+      if (t.type != token_type::word || t.value.empty () ||
+          (tt != token_type::assign  &&
+           tt != token_type::prepend &&
+           tt != token_type::append))
+      {
+        fail << "expected variable assignment instead of '" << s << "'" <<
+          info << "use double '--' to treat this argument as buildspec";
+      }
+
+      // Take care of the visibility. Note that here we rely on the fact that
+      // none of these characters are lexer's name separators.
+      //
+      char c (t.value[0]);
+
+      if (path::traits_type::is_separator (c))
+        c = '/'; // Normalize.
+
+      string n (t.value, c == '!' || c == '%' || c == '/' ? 1 : 0);
+
+      if (c == '!' && dir)
+        fail << "scope-qualified global override of variable " << n;
+
+      variable& var (const_cast<variable&> (
+                       vp.insert (n, true /* overridable */)));
+
+      const variable* o;
+      {
+        variable_visibility v (c == '/' ? variable_visibility::scope   :
+                               c == '%' ? variable_visibility::project :
+                               variable_visibility::normal);
+
+        const char* k (tt == token_type::assign ? "__override" :
+                       tt == token_type::append ? "__suffix" : "__prefix");
+
+        unique_ptr<variable> p (
+          new variable {
+            n + '.' + to_string (i + 1) + '.' + k,
+            nullptr /* aliases   */,
+            nullptr /* type      */,
+            nullptr /* overrides */,
+            v});
+
+        // Back link.
+        //
+        p->aliases = p.get ();
+        if (var.overrides != nullptr)
+          swap (p->aliases,
+                const_cast<variable*> (var.overrides.get ())->aliases);
+
+        // Forward link.
+        //
+        p->overrides = move (var.overrides);
+        var.overrides = move (p);
+
+        o = var.overrides.get ();
+      }
+
+      // Currently we expand project overrides in the global scope to keep
+      // things simple. Pass original variable for diagnostics. Use current
+      // working directory as pattern base.
+      //
+      parser p;
+      pair<value, token> r (p.parse_variable_value (l, gs, &work, var));
+
+      if (r.second.type != token_type::eos)
+        fail << "unexpected " << r.second << " in variable assignment "
+             << "'" << s << "'";
+
+      // Make sure the value is not typed.
+      //
+      if (r.first.type != nullptr)
+        fail << "typed override of variable " << n;
+
+      // Global and absolute scope overrides we can enter directly. Project
+      // and relative scope ones will be entered by the caller for each
+      // amalgamation/project.
+      //
+      if (c == '!' || (dir && dir->absolute ()))
+      {
+        scope& s (c == '!' ? gs : sm.insert (*dir)->second);
+
+        auto p (s.vars.insert (*o));
+        assert (p.second); // Variable name is unique.
+
+        value& v (p.first);
+        v = move (r.first);
+      }
+      else
+        vos.push_back (
+          variable_override {var, *o, move (dir), move (r.first)});
+    }
+
+    // Enter builtin variables and patterns.
+    //
+
+    // All config. variables are by default overridable.
+    //
+    vp.insert_pattern ("config.**", nullopt, true, nullopt, true, false);
+
+    // file.cxx:import() (note that order is important; see insert_pattern()).
+    //
+    vp.insert_pattern<abs_dir_path> (
+      "config.import.*", true, variable_visibility::normal, true);
+    vp.insert_pattern<path> (
+      "config.import.**", true, variable_visibility::normal, true);
+
+    // module.cxx:load_module().
+    //
+    {
+      auto v_p (variable_visibility::project);
+
+      vp.insert_pattern<bool> ("**.booted", false, v_p);
+      vp.insert_pattern<bool> ("**.loaded", false, v_p);
+      vp.insert_pattern<bool> ("**.configured", false, v_p);
+    }
+
+    {
+      auto v_p (variable_visibility::project);
+      auto v_t (variable_visibility::target);
+      auto v_q (variable_visibility::prereq);
+
+      var_src_root = &vp.insert<dir_path> ("src_root");
+      var_out_root = &vp.insert<dir_path> ("out_root");
+      var_src_base = &vp.insert<dir_path> ("src_base");
+      var_out_base = &vp.insert<dir_path> ("out_base");
+
+      var_forwarded = &vp.insert<bool> ("forwarded", v_p);
+
+      // Note that subprojects is not typed since the value requires
+      // pre-processing (see file.cxx).
+      //
+      var_project      = &vp.insert<project_name> ("project",      v_p);
+      var_amalgamation = &vp.insert<dir_path>     ("amalgamation", v_p);
+      var_subprojects  = &vp.insert               ("subprojects",  v_p);
+      var_version      = &vp.insert<string>       ("version",      v_p);
+
+      var_project_url     = &vp.insert<string> ("project.url",     v_p);
+      var_project_summary = &vp.insert<string> ("project.summary", v_p);
+
+      var_import_target = &vp.insert<name> ("import.target");
+
+      var_clean    = &vp.insert<bool>   ("clean",    v_t);
+      var_backlink = &vp.insert<string> ("backlink", v_t);
+      var_include  = &vp.insert<string> ("include",  v_q);
+
+      vp.insert<string> (var_extension, v_t);
+
+      // Backlink executables and (generated) documentation by default.
+      //
+      gs.target_vars[exe::static_type]["*"].assign (var_backlink) = "true";
+      gs.target_vars[doc::static_type]["*"].assign (var_backlink) = "true";
+
+      var_build_meta_operation = &vp.insert<string> ("build.meta_operation");
+    }
+
+    // Register builtin rules.
+    //
+    {
+      rule_map& r (gs.rules); // Note: global scope!
+
+      //@@ outer
+      r.insert<alias> (perform_id, 0, "alias", alias_rule::instance);
+
+      r.insert<fsdir> (perform_update_id, "fsdir", fsdir_rule::instance);
+      r.insert<fsdir> (perform_clean_id, "fsdir", fsdir_rule::instance);
+
+      r.insert<mtime_target> (perform_update_id, "file", file_rule::instance);
+      r.insert<mtime_target> (perform_clean_id, "file", file_rule::instance);
+    }
+
+    return vos;
+  }
+
+  dir_path
+  src_out (const dir_path& out, const scope& r)
+  {
+    assert (r.root ());
+    return src_out (out, r.out_path (), r.src_path ());
+  }
+
+  dir_path
+  out_src (const dir_path& src, const scope& r)
+  {
+    assert (r.root ());
+    return out_src (src, r.out_path (), r.src_path ());
+  }
+
+  dir_path
+  src_out (const dir_path& o,
+           const dir_path& out_root, const dir_path& src_root)
+  {
+    assert (o.sub (out_root));
+    return src_root / o.leaf (out_root);
+  }
+
+  dir_path
+  out_src (const dir_path& s,
+           const dir_path& out_root, const dir_path& src_root)
+  {
+    assert (s.sub (src_root));
+    return out_root / s.leaf (src_root);
+  }
+
+  // diag_do(), etc.
+  //
+  string
+  diag_do (const action&)
+  {
+    const meta_operation_info& m (*current_mif);
+    const operation_info& io (*current_inner_oif);
+    const operation_info* oo (current_outer_oif);
+
+    string r;
+
+    // perform(update(x))   -> "update x"
+    // configure(update(x)) -> "configure updating x"
+    //
+    if (m.name_do.empty ())
+      r = io.name_do;
+    else
+    {
+      r = m.name_do;
+
+      if (io.name_doing[0] != '\0')
+      {
+        r += ' ';
+        r += io.name_doing;
+      }
+    }
+
+    if (oo != nullptr)
+    {
+      r += " (for ";
+      r += oo->name;
+      r += ')';
+    }
+
+    return r;
+  }
+
+  void
+  diag_do (ostream& os, const action& a, const target& t)
+  {
+    os << diag_do (a) << ' ' << t;
+  }
+
+  string
+  diag_doing (const action&)
+  {
+    const meta_operation_info& m (*current_mif);
+    const operation_info& io (*current_inner_oif);
+    const operation_info* oo (current_outer_oif);
+
+    string r;
+
+    // perform(update(x))   -> "updating x"
+    // configure(update(x)) -> "configuring updating x"
+    //
+    if (!m.name_doing.empty ())
+      r = m.name_doing;
+
+    if (io.name_doing[0] != '\0')
+    {
+      if (!r.empty ()) r += ' ';
+      r += io.name_doing;
+    }
+
+    if (oo != nullptr)
+    {
+      r += " (for ";
+      r += oo->name;
+      r += ')';
+    }
+
+    return r;
+  }
+
+  void
+  diag_doing (ostream& os, const action& a, const target& t)
+  {
+    os << diag_doing (a) << ' ' << t;
+  }
+
+  string
+  diag_did (const action&)
+  {
+    const meta_operation_info& m (*current_mif);
+    const operation_info& io (*current_inner_oif);
+    const operation_info* oo (current_outer_oif);
+
+    string r;
+
+    // perform(update(x))   -> "updated x"
+    // configure(update(x)) -> "configured updating x"
+    //
+    if (!m.name_did.empty ())
+    {
+      r = m.name_did;
+
+      if (io.name_doing[0] != '\0')
+      {
+        r += ' ';
+        r += io.name_doing;
+      }
+    }
+    else
+      r += io.name_did;
+
+    if (oo != nullptr)
+    {
+      r += " (for ";
+      r += oo->name;
+      r += ')';
+    }
+
+    return r;
+  }
+
+  void
+  diag_did (ostream& os, const action& a, const target& t)
+  {
+    os << diag_did (a) << ' ' << t;
+  }
+
+  void
+  diag_done (ostream& os, const action&, const target& t)
+  {
+    const meta_operation_info& m (*current_mif);
+    const operation_info& io (*current_inner_oif);
+    const operation_info* oo (current_outer_oif);
+
+    // perform(update(x))   -> "x is up to date"
+    // configure(update(x)) -> "updating x is configured"
+    //
+    if (m.name_done.empty ())
+    {
+      os << t;
+
+      if (io.name_done[0] != '\0')
+        os << ' ' << io.name_done;
+
+      if (oo != nullptr)
+        os << " (for " << oo->name << ')';
+    }
+    else
+    {
+      if (io.name_doing[0] != '\0')
+        os << io.name_doing << ' ';
+
+      if (oo != nullptr)
+        os << "(for " << oo->name << ") ";
+
+      os << t << ' ' << m.name_done;
+    }
+  }
+}