path: root/libbuild2/adhoc-rule-buildscript.cxx

// file      : libbuild2/adhoc-rule-buildscript.cxx -*- C++ -*-
// license   : MIT; see accompanying LICENSE file

#include <libbuild2/adhoc-rule-buildscript.hxx>

#include <sstream>

#include <libbuild2/depdb.hxx>
#include <libbuild2/scope.hxx>
#include <libbuild2/target.hxx>
#include <libbuild2/dyndep.hxx>
#include <libbuild2/context.hxx>
#include <libbuild2/algorithm.hxx>
#include <libbuild2/filesystem.hxx>  // path_perms(), auto_rmfile
#include <libbuild2/diagnostics.hxx>

#include <libbuild2/parser.hxx> // attributes

#include <libbuild2/build/script/parser.hxx>
#include <libbuild2/build/script/runner.hxx>

using namespace std;

namespace build2
{
  static inline void
  hash_script_vars (sha256& cs,
                    const build::script::script& s,
                    const target& t,
                    names& storage)
  {
    context& ctx (t.ctx);

    for (const string& n: s.vars)
    {
      cs.append (n);

      lookup l;

      if (const variable* var = ctx.var_pool.find (n))
        l = t[var];

      cs.append (!l.defined () ? '\x1' : l->null ? '\x2' : '\x3');

      if (l)
      {
        storage.clear ();
        names_view ns (reverse (*l, storage));

        for (const name& n: ns)
          to_checksum (cs, n);
      }
    }
  }

  // How should we hash target and prerequisite sets ($> and $<)? We could
  // hash them as target names (i.e., the same as the $>/< content) or as
  // paths (only for path-based targets). While names feel more general, they
  // are also more expensive to compute. And for path-based targets, path is
  // generally a good proxy for the target name. Since the bulk of the ad hoc
  // recipes will presumably be operating exclusively on path-based targets,
  // let's do it both ways.
  //
  static inline void
  hash_target (sha256& cs, const target& t, names& storage)
  {
    if (const path_target* pt = t.is_a<path_target> ())
      cs.append (pt->path ().string ());
    else
    {
      storage.clear ();
      t.as_name (storage);
      for (const name& n: storage)
        to_checksum (cs, n);
    }
  };

  // The script can reference a program in one of four ways:
  //
  // 1. As an (imported) target (e.g., $cli)
  //
  // 2. As a process_path_ex (e.g., $cxx.path).
  //
  // 3. As a builtin (e.g., sed)
  //
  // 4. As a program path/name.
  //
  // When it comes to change tracking, there is nothing we can do for (4) (the
  // user can track its environment manually with depdb-env) and there is
  // nothing to do for (3) (assuming builtin semantics is stable/backwards-
  // compatible). The (2) case is handled automatically by hashing all the
  // variable values referenced by the script (see below), which in case of
  // process_path_ex includes the checksums (both executable and environment),
  // if available.
  //
  // This leaves the (1) case, which itself splits into two sub-cases: the
  // target comes with the dependency information (e.g., imported from a
  // project via an export stub) or it does not (e.g., imported as installed).
  // We don't need to do anything extra for the first sub-case since the
  // target's state/mtime can be relied upon like any other prerequisite.
  // Which cannot be said about the second sub-case, where we reply on
  // checksum that may be included as part of the target metadata.
  //
  // So what we are going to do is hash checksum metadata of every executable
  // prerequisite target that has it (we do it here in order to include ad hoc
  // prerequisites, which feels like the right thing to do; the user may mark
  // tools as ad hoc in order to omit them from $<).
  //
  static inline void
  hash_prerequisite_target (sha256& cs, sha256& exe_cs, sha256& env_cs,
                            const target& pt,
                            names& storage)
  {
    hash_target (cs, pt, storage);

    if (const exe* et = pt.is_a<exe> ())
    {
      if (const string* c = et->lookup_metadata<string> ("checksum"))
      {
        exe_cs.append (*c);
      }

      if (const strings* e = et->lookup_metadata<strings> ("environment"))
      {
        hash_environment (env_cs, *e);
      }
    }
  }

  bool adhoc_buildscript_rule::
  recipe_text (const scope& s,
               const target_type& tt,
               string&& t,
               attributes& as)
  {
    // Handle and erase recipe-specific attributes.
    //
    optional<string> diag;
    for (auto i (as.begin ()); i != as.end (); )
    {
      attribute& a (*i);
      const string& n (a.name);

      if (n == "diag")
      try
      {
        diag = convert<string> (move (a.value));
      }
      catch (const invalid_argument& e)
      {
        fail (as.loc) << "invalid " << n << " attribute value: " << e;
      }
      else
      {
        ++i;
        continue;
      }

      i = as.erase (i);
    }

    checksum = sha256 (t).string ();
    ttype = &tt;

    istringstream is (move (t));
    build::script::parser p (s.ctx);

    script = p.pre_parse (s, tt, actions,
                          is, loc.file, loc.line + 1,
                          move (diag), as.loc);

    return false;
  }

  void adhoc_buildscript_rule::
  dump_attributes (ostream& os) const
  {
    // For now we dump it as an attribute whether it was specified or derived
    // from the script. Maybe that's ok (we use this in tests)?
    //
    if (script.diag_name)
    {
      os << " [";
      os << "diag=";
      to_stream (os, name (*script.diag_name), true /* quote */, '@');
      os << ']';
    }
  }

  void adhoc_buildscript_rule::
  dump_text (ostream& os, string& ind) const
  {
    os << ind << string (braces, '{') << endl;
    ind += "  ";

    if (script.depdb_clear)
      os << ind << "depdb clear" << endl;

    script::dump (os, ind, script.depdb_preamble);

    if (script.diag_line)
    {
      os << ind; script::dump (os, *script.diag_line, true /* newline */);
    }

    script::dump (os, ind, script.body);
    ind.resize (ind.size () - 2);
    os << ind << string (braces, '}');
  }

  bool adhoc_buildscript_rule::
  reverse_fallback (action a, const target_type& tt) const
  {
    // We can provide clean for a file target if we are providing update.
    //
    return a == perform_clean_id && tt.is_a<file> () &&
      find (actions.begin (), actions.end (),
            perform_update_id) != actions.end ();
  }

  struct adhoc_buildscript_rule::match_data
  {
    match_data (action a, const target& t, bool temp_dir)
        : env (a, t, temp_dir) {}

    build::script::environment env;
    build::script::default_runner run;

    path dd;
    const scope* bs;
    timestamp mt;
    bool deferred_failure;
  };

  bool adhoc_buildscript_rule::
  match (action a, target& t, const string& h, match_extra& me) const
  {
    // We pre-parsed the script with the assumption it will be used on a
    // non/file-based target. Note that this should not be possible with
    // patterns.
    //
    if (pattern == nullptr)
    {
      if ((t.is_a<file> () != nullptr) != ttype->is_a<file> ())
      {
        fail (loc) << "incompatible target types used with shared recipe" <<
          info << "all targets must be file-based or non-file-based";
      }
    }

    return adhoc_rule::match (a, t, h, me);
  }

  recipe adhoc_buildscript_rule::
  apply (action a, target& t, match_extra& me) const
  {
    return apply (a, t, me, nullopt);
  }

  recipe adhoc_buildscript_rule::
  apply (action a,
         target& xt,
         match_extra& me,
         const optional<timestamp>& d) const
  {
    tracer trace ("adhoc_buildscript_rule::apply");

    // We don't support deadlines for any of these cases (see below).
    //
    if (d && (a.outer ()  ||
              me.fallback ||
              (a == perform_update_id && xt.is_a<file> ())))
      return empty_recipe;

    // If this is an outer operation (e.g., update-for-test), then delegate to
    // the inner.
    //
    if (a.outer ())
    {
      match_inner (a, xt);
      return execute_inner;
    }

    // Inject pattern's ad hoc group members, if any.
    //
    if (pattern != nullptr)
      pattern->apply_adhoc_members (a, xt, me);

    // Derive file names for the target and its ad hoc group members, if any.
    //
    if (a == perform_update_id || a == perform_clean_id)
    {
      for (target* m (&xt); m != nullptr; m = m->adhoc_member)
      {
        if (auto* p = m->is_a<path_target> ())
          p->derive_path ();
      }
    }

    // Inject dependency on the output directory.
    //
    // We do it always instead of only if one of the targets is path-based in
    // case the recipe creates temporary files or some such.
    //
    const fsdir* dir (inject_fsdir (a, xt));

    // Match prerequisites.
    //
    match_prerequisite_members (a, xt);

    // Inject pattern's prerequisites, if any.
    //
    if (pattern != nullptr)
      pattern->apply_prerequisites (a, xt, me);

    // See if we are providing the standard clean as a fallback.
    //
    if (me.fallback)
      return &perform_clean_depdb;

    // See if this is not update or not on a file-based target.
    //
    if (a != perform_update_id || !xt.is_a<file> ())
    {
      return [d, this] (action a, const target& t)
      {
        return default_action (a, t, d);
      };
    }

    // See if this is the simple case with only static dependencies.
    //
    if (!script.depdb_dyndep)
    {
      return [this] (action a, const target& t)
      {
        return perform_update_file (a, t);
      };
    }

    // This is a perform update on a file target with extraction of dynamic
    // dependency information in the depdb preamble (depdb-dyndep).
    //
    // This means we may need to add additional prerequisites (or even target
    // group members). We also have to save any such additional prerequisites
    // in depdb so that we can check if any of them have changed on subsequent
    // updates. So all this means that have to take care of depdb here in
    // apply() instead of perform_*() like we normally do. We also do things
    // in slightly different order due to the restrictions impose by the match
    // phase.
    //
    // Note that the C/C++ header dependency extraction is the canonical
    // example and all this logic is based on the prior work in the cc module
    // where you can often find more detailed rationale for some of the steps
    // performed (like the fsdir update below).
    //
    context& ctx (xt.ctx);

    file& t (xt.as<file> ());
    const path& tp (t.path ());

    if (dir != nullptr)
      fsdir_rule::perform_update_direct (a, t);

    // Because the depdb preamble can access $<, we have to blank out all the
    // ad hoc prerequisites. Since we will still need them later, we "move"
    // them to the auxiliary data member in prerequisite_target (which also
    // means we cannot use the standard execute_prerequisites()).
    //
    auto& pts (t.prerequisite_targets[a]);
    for (prerequisite_target& p: pts)
    {
      // Note that fsdir{} injected above is adhoc.
      //
      if (p.target != nullptr && p.adhoc)
      {
        p.data = reinterpret_cast<uintptr_t> (p.target);
        p.target = nullptr;
      }
    }

    // NOTE: see the "static dependencies" version (with comments) below.
    //
    depdb dd (tp + ".d");

    if (dd.expect ("<ad hoc buildscript recipe> 1") != nullptr)
      l4 ([&]{trace << "rule mismatch forcing update of " << t;});

    if (dd.expect (checksum) != nullptr)
      l4 ([&]{trace << "recipe text change forcing update of " << t;});

    if (!script.depdb_clear)
    {
      names storage;

      sha256 prq_cs, exe_cs, env_cs;

      for (const prerequisite_target& p: pts)
      {
        if (const target* pt =
            (p.target != nullptr ? p.target :
             p.data   != 0       ? reinterpret_cast<target*> (p.data) :
             nullptr))
        {
          hash_prerequisite_target (prq_cs, exe_cs, env_cs, *pt, storage);
        }
      }

      {
        sha256 cs;
        hash_script_vars (cs, script, t, storage);

        if (dd.expect (cs.string ()) != nullptr)
          l4 ([&]{trace << "recipe variable change forcing update of " << t;});
      }

      {
        sha256 tcs;
        for (const target* m (&t); m != nullptr; m = m->adhoc_member)
          hash_target (tcs, *m, storage);

        if (dd.expect (tcs.string ()) != nullptr)
          l4 ([&]{trace << "target set change forcing update of " << t;});

        if (dd.expect (prq_cs.string ()) != nullptr)
          l4 ([&]{trace << "prerequisite set change forcing update of " << t;});
      }

      {
        if (dd.expect (exe_cs.string ()) != nullptr)
          l4 ([&]{trace << "program checksum change forcing update of " << t;});

        if (dd.expect (env_cs.string ()) != nullptr)
          l4 ([&]{trace << "environment change forcing update of " << t;});
      }
    }

    const scope& bs (t.base_scope ());

    unique_ptr<match_data> md (
      new match_data (a, t, script.depdb_preamble_temp_dir));

    build::script::environment& env (md->env);
    build::script::default_runner& run (md->run);

    run.enter (env, script.start_loc);

    // Run the first half of the preamble (before depdb-dyndep).
    //
    {
      build::script::parser p (ctx);
      p.execute_depdb_preamble (a, bs, t, env, script, run, dd);
    }

    // Determine if we need to do an update based on the above checks.
    //
    bool update;
    timestamp mt;

    if (dd.writing ())
      update = true;
    else
    {
      if ((mt = t.mtime ()) == timestamp_unknown)
        t.mtime (mt = mtime (tp)); // Cache.

      update = dd.mtime > mt;
    }

    if (update)
      mt = timestamp_nonexistent;

    // Update our prerequisite targets. While strictly speaking we only need
    // to update those that are referenced by depdb-dyndep, communicating
    // this is both tedious and error-prone. So we update them all.
    //
    for (const prerequisite_target& p: pts)
    {
      if (const target* pt =
          (p.target != nullptr ? p.target :
           p.data   != 0       ? reinterpret_cast<target*> (p.data) : nullptr))
      {
        update = dyndep_rule::update (
          trace, a, *pt, update ? timestamp_unknown : mt) || update;
      }
    }

    // Run the second half of the preamble (depdb-dyndep commands) to extract
    // dynamic dependencies.
    //
    // Note that this should be the last update to depdb (the invalidation
    // order semantics).
    //
    bool deferred_failure (false);
    {
      build::script::parser p (ctx);
      p.execute_depdb_preamble_dyndep (a, bs, t,
                                       env, script, run,
                                       dd,
                                       update,
                                       deferred_failure,
                                       mt);
    }

    if (update && dd.reading () && !ctx.dry_run)
      dd.touch = true;

    dd.close ();
    md->dd = move (dd.path);

    // Pass on base scope and update/mtime.
    //
    md->bs = &bs;
    md->mt = update ? timestamp_nonexistent : mt;
    md->deferred_failure = deferred_failure;

    // @@ TMP: re-enable once recipe becomes move_only_function.
    //
#if 0
    return [this, md = move (md)] (action a, const target& t) mutable
    {
      auto r (perform_update_file_dyndep (a, t, *md));
      md.reset (); // @@ TMP: is this really necessary (+mutable)?
      return r;
    };
#else
    t.data (move (md));
    return recipe ([this] (action a, const target& t) mutable
    {
      auto md (move (t.data<unique_ptr<match_data>> ()));
      return perform_update_file_dyndep (a, t, *md);
    });
#endif
  }

  target_state adhoc_buildscript_rule::
  perform_update_file_dyndep (action a, const target& xt, match_data& md) const
  {
    tracer trace ("adhoc_buildscript_rule::perform_update_file_dyndep");

    context& ctx (xt.ctx);

    const file& t (xt.as<file> ());
    const path& tp (t.path ());

    // While we've updated all our prerequisites in apply(), we still need to
    // execute them here to keep the dependency counts straight.
    //
    for (const prerequisite_target& p: t.prerequisite_targets[a])
    {
      if (const target* pt =
          (p.target != nullptr ? p.target :
           p.data   != 0       ? reinterpret_cast<target*> (p.data) : nullptr))
      {
        target_state ts (execute_wait (a, *pt));
        assert (ts == target_state::unchanged || ts == target_state::changed);
      }
    }

    build::script::environment& env (md.env);
    build::script::default_runner& run (md.run);

    // Force update in case of a deferred failure even if nothing changed.
    //
    if (md.mt != timestamp_nonexistent && !md.deferred_failure)
    {
      run.leave (env, script.end_loc);
      return target_state::unchanged;
    }

    // Sequence start time for mtime checks below.
    //
    timestamp start (!ctx.dry_run && depdb::mtime_check ()
                     ? system_clock::now ()
                     : timestamp_unknown);

    if (!ctx.dry_run || verb != 0)
    {
      if (execute_update_file (*md.bs, a, t, env, run, md.deferred_failure))
        ;
      else
        run.leave (env, script.end_loc);
    }
    else
      run.leave (env, script.end_loc);

    timestamp now (system_clock::now ());

    if (!ctx.dry_run)
      depdb::check_mtime (start, md.dd, tp, now);

    t.mtime (now);
    return target_state::changed;
  }

  target_state adhoc_buildscript_rule::
  perform_update_file (action a, const target& xt) const
  {
    tracer trace ("adhoc_buildscript_rule::perform_update_file");

    context& ctx (xt.ctx);

    const file& t (xt.as<file> ());
    const path& tp (t.path ());

    // Update prerequisites and determine if any of them render this target
    // out-of-date.
    //
    timestamp mt (t.load_mtime ());
    optional<target_state> ps;

    names storage;

    sha256 prq_cs, exe_cs, env_cs;
    {
      // This is essentially ps=execute_prerequisites(a, t, mt) which we
      // cannot use because we need to see ad hoc prerequisites.
      //
      size_t busy (ctx.count_busy ());
      size_t exec (ctx.count_executed ());

      target_state rs (target_state::unchanged);

      wait_guard wg (ctx, busy, t[a].task_count);

      auto& pts (t.prerequisite_targets[a]);

      for (const target*& pt: pts)
      {
        if (pt == nullptr) // Skipped.
          continue;

        target_state s (execute_async (a, *pt, busy, t[a].task_count));

        if (s == target_state::postponed)
        {
          rs |= s;
          pt = nullptr;
        }
      }

      wg.wait ();

      bool e (mt == timestamp_nonexistent);
      for (prerequisite_target& p: pts)
      {
        if (p == nullptr)
          continue;

        const target& pt (*p.target);

        ctx.sched.wait (exec, pt[a].task_count, scheduler::work_none);

        target_state s (pt.executed_state (a));
        rs |= s;

        // Compare our timestamp to this prerequisite's.
        //
        if (!e)
        {
          // If this is an mtime-based target, then compare timestamps.
          //
          if (const mtime_target* mpt = pt.is_a<mtime_target> ())
          {
            if (mpt->newer (mt, s))
              e = true;
          }
          else
          {
            // Otherwise we assume the prerequisite is newer if it was
            // changed.
            //
            if (s == target_state::changed)
              e = true;
          }
        }

        if (p.adhoc)
          p.target = nullptr; // Blank out.

        // As part of this loop calculate checksums that need to include ad
        // hoc prerequisites (unless the script tracks changes itself).
        //
        if (!script.depdb_clear)
          hash_prerequisite_target (prq_cs, exe_cs, env_cs, pt, storage);
      }

      if (!e)
        ps = rs;
    }

    bool update (!ps);

    // We use depdb to track changes to the script itself, input/output file
    // names, tools, etc.
    //
    // NOTE: see the "dynamic dependencies" version above.
    //
    depdb dd (tp + ".d");

    // First should come the rule name/version.
    //
    if (dd.expect ("<ad hoc buildscript recipe> 1") != nullptr)
      l4 ([&]{trace << "rule mismatch forcing update of " << t;});

    // Then the script checksum.
    //
    // Ideally, to detect changes to the script semantics, we would hash the
    // text with all the variables expanded but without executing any
    // commands. In practice, this is easier said than done (think the set
    // builtin that receives output of a command that modifies the
    // filesystem).
    //
    // So as the next best thing we are going to hash the unexpanded text as
    // well as values of all the variables expanded in it (which we get as a
    // side effect of pre-parsing the script). This approach has a number of
    // drawbacks:
    //
    // - We can't handle computed variable names (e.g., $($x ? X : Y)).
    //
    // - We may "overhash" by including variables that are actually
    //   script-local.
    //
    // - There are functions like $install.resolve() with result based on
    //   external (to the script) information.
    //
    if (dd.expect (checksum) != nullptr)
      l4 ([&]{trace << "recipe text change forcing update of " << t;});

    // Track the variables, targets, and prerequisites changes, unless the
    // script tracks the dependency changes itself.
    //
    if (!script.depdb_clear)
    {
      // For each variable hash its name, undefined/null/non-null indicator,
      // and the value if non-null.
      //
      // Note that this excludes the special $< and $> variables which we
      // handle below.
      //
      // @@ TODO: maybe detect and decompose process_path_ex in order to
      //    properly attribute checksum and environment changes?
      //
      {
        sha256 cs;
        hash_script_vars (cs, script, t, storage);

        if (dd.expect (cs.string ()) != nullptr)
          l4 ([&]{trace << "recipe variable change forcing update of " << t;});
      }

      // Target and prerequisite sets ($> and $<).
      //
      {
        sha256 tcs;
        for (const target* m (&t); m != nullptr; m = m->adhoc_member)
          hash_target (tcs, *m, storage);

        if (dd.expect (tcs.string ()) != nullptr)
          l4 ([&]{trace << "target set change forcing update of " << t;});

        if (dd.expect (prq_cs.string ()) != nullptr)
          l4 ([&]{trace << "prerequisite set change forcing update of " << t;});
      }

      // Finally the programs and environment checksums.
      //
      {
        if (dd.expect (exe_cs.string ()) != nullptr)
          l4 ([&]{trace << "program checksum change forcing update of " << t;});

        if (dd.expect (env_cs.string ()) != nullptr)
          l4 ([&]{trace << "environment change forcing update of " << t;});
      }
    }

    const scope* bs (nullptr);

    // Execute the custom dependency change tracking commands, if present.
    //
    // Note that we share the environment between the execute_depdb_preamble()
    // and execute_body() calls, which is not merely an optimization since
    // variables set in the preamble must be available in the body.
    //
    // Creating the environment instance is not cheap so optimize for the
    // common case where we don't have the depdb preamble and nothing to
    // update.
    //
    bool depdb_preamble (!script.depdb_preamble.empty ());

    if (!depdb_preamble)
    {
      if (dd.writing () || dd.mtime > mt)
        update = true;

      if (!update)
      {
        dd.close ();
        return *ps;
      }
    }

    build::script::environment env (a, t, false /* temp_dir */);
    build::script::default_runner run;

    if (depdb_preamble)
    {
      bs = &t.base_scope ();

      if (script.depdb_preamble_temp_dir)
        env.set_temp_dir_variable ();

      build::script::parser p (ctx);

      run.enter (env, script.start_loc);
      p.execute_depdb_preamble (a, *bs, t, env, script, run, dd);
    }

    // Update if depdb mismatch.
    //
    if (dd.writing () || dd.mtime > mt)
      update = true;

    dd.close ();

    // If nothing changed, then we are done.
    //
    if (!update)
    {
      // Note that if we execute the depdb preamble but not the script body,
      // we need to call the runner's leave() function explicitly (here and
      // below).
      //
      if (depdb_preamble)
        run.leave (env, script.end_loc);

      return *ps;
    }

    if (!ctx.dry_run || verb != 0)
    {
      // Prepare to execute the script diag line and/or body.
      //
      if (bs == nullptr)
        bs = &t.base_scope ();

      if (execute_update_file (*bs, a, t, env, run))
      {
        if (!ctx.dry_run)
          dd.check_mtime (tp);
      }
      else if (depdb_preamble)
        run.leave (env, script.end_loc);
    }
    else if (depdb_preamble)
      run.leave (env, script.end_loc);

    t.mtime (system_clock::now ());
    return target_state::changed;
  }

  bool adhoc_buildscript_rule::
  execute_update_file (const scope& bs,
                       action, const file& t,
                       build::script::environment& env,
                       build::script::default_runner& run,
                       bool deferred_failure) const
  {
    context& ctx (t.ctx);

    const scope& rs (*bs.root_scope ());

    // Note that it doesn't make much sense to use the temporary directory
    // variable ($~) in the 'diag' builtin call, so we postpone setting it
    // until the script body execution, that can potentially be omitted.
    //
    build::script::parser p (ctx);

    if (verb == 1)
    {
      if (script.diag_line)
      {
        text << p.execute_special (rs, bs, env, *script.diag_line);
      }
      else
      {
        // @@ TODO (and in default_action() below):
        //
        // - we are printing target, not source (like in most other places)
        //
        // - printing of ad hoc target group (the {hxx cxx}{foo} idea)
        //
        // - if we are printing prerequisites, should we print all of them
        //   (including tools)?
        //
        text << *script.diag_name << ' ' << t;
      }
    }

    if (!ctx.dry_run || verb >= 2)
    {
      // On failure remove the target files that may potentially exist but
      // be invalid.
      //
      small_vector<auto_rmfile, 8> rms;

      if (!ctx.dry_run)
      {
        for (const target* m (&t); m != nullptr; m = m->adhoc_member)
        {
          if (auto* f = m->is_a<file> ())
            rms.emplace_back (f->path ());
        }
      }

      if (script.body_temp_dir && !script.depdb_preamble_temp_dir)
        env.set_temp_dir_variable ();

      p.execute_body (rs, bs, env, script, run, script.depdb_preamble.empty ());

      if (!ctx.dry_run)
      {
        if (deferred_failure)
          fail << "expected error exit status from recipe body";

        // If this is an executable, let's be helpful to the user and set
        // the executable bit on POSIX.
        //
#ifndef _WIN32
        auto chmod = [] (const path& p)
        {
          path_perms (p,
                      (path_perms (p)  |
                       permissions::xu |
                       permissions::xg |
                       permissions::xo));
        };

        for (const target* m (&t); m != nullptr; m = m->adhoc_member)
        {
          if (auto* p = m->is_a<exe> ())
            chmod (p->path ());
        }
#endif
        for (auto& rm: rms)
          rm.cancel ();
      }

      return true;
    }
    else
      return false;
  }

  target_state adhoc_buildscript_rule::
  default_action (action a,
                  const target& t,
                  const optional<timestamp>& deadline) const
  {
    tracer trace ("adhoc_buildscript_rule::default_action");

    context& ctx (t.ctx);

    execute_prerequisites (a, t);

    if (!ctx.dry_run || verb != 0)
    {
      const scope& bs (t.base_scope ());
      const scope& rs (*bs.root_scope ());

      build::script::environment e (a, t, script.body_temp_dir, deadline);
      build::script::parser p (ctx);

      if (verb == 1)
      {
        if (script.diag_line)
        {
          text << p.execute_special (rs, bs, e, *script.diag_line);
        }
        else
        {
          // @@ TODO: as above (execute_update_file()).
          //
          text << *script.diag_name << ' ' << t;
        }
      }

      if (!ctx.dry_run || verb >= 2)
      {
        build::script::default_runner r;
        p.execute_body (rs, bs, e, script, r);
      }
    }

    return target_state::changed;
  }
}