From dfd19b9637c6b917a40413a57b391d7ff27f50da Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 26 Mar 2020 07:03:50 +0200
Subject: Make buildfile parser reset'able

Note that the testscript parser (which derives from the buildfile parser) is
(still) not reset'able (this functionality is currently not needed so why
complicate things).
---
 libbuild2/parser.cxx | 44 ++++++++++++++++++++++++++++++++------------
 libbuild2/parser.hxx | 32 +++++++++++++++++++++++---------
 2 files changed, 55 insertions(+), 21 deletions(-)

diff --git a/libbuild2/parser.cxx b/libbuild2/parser.cxx
index fbf3bda..2cb51c6 100644
--- a/libbuild2/parser.cxx
+++ b/libbuild2/parser.cxx
@@ -212,6 +212,17 @@ namespace build2
   };
 
   void parser::
+  reset ()
+  {
+    pre_parse_ = false;
+    attributes_.clear ();
+    default_target_ = nullptr;
+    peeked_ = false;
+    replay_ = replay::stop;
+    replay_data_.clear ();
+  }
+
+  void parser::
   parse_buildfile (istream& is, const path_name& in, scope& root, scope& base)
   {
     lexer l (is, in);
@@ -223,12 +234,13 @@ namespace build2
   {
     path_ = &l.name ();
     lexer_ = &l;
+
     root_ = &root;
     scope_ = &base;
-    pbase_ = scope_->src_path_;
     target_ = nullptr;
     prerequisite_ = nullptr;
-    default_target_ = nullptr;
+
+    pbase_ = scope_->src_path_;
 
     enter_buildfile (*path_); // Needs scope_.
 
@@ -249,11 +261,14 @@ namespace build2
   {
     path_ = &l.name ();
     lexer_ = &l;
+
+    root_ = nullptr;
     scope_ = &s;
-    pbase_ = scope_->src_path_; // Normally NULL.
     target_ = nullptr;
     prerequisite_ = nullptr;
 
+    pbase_ = scope_->src_path_; // Normally NULL.
+
     token t;
     type tt;
     parse_variable (t, tt, var, kind);
@@ -268,11 +283,14 @@ namespace build2
   {
     path_ = &l.name ();
     lexer_ = &l;
+
+    root_ = nullptr;
     scope_ = &s;
-    pbase_ = b;
     target_ = nullptr;
     prerequisite_ = nullptr;
 
+    pbase_ = b;
+
     token t;
     type tt;
     value rhs (parse_variable_value (t, tt));
@@ -1968,9 +1986,9 @@ namespace build2
     if (val.type != nullptr)
       untypify (val);
 
-    export_value_ = move (val).as<names> ();
+    export_value = move (val).as<names> ();
 
-    if (export_value_.empty ())
+    if (export_value.empty ())
       fail (l) << "empty value in export";
 
     next_after_newline (t, tt);
@@ -3675,7 +3693,7 @@ namespace build2
     bool has (tt == type::lsbrace);
 
     if (!pre_parse_)
-      attributes_.push (attributes {has, l, {}});
+      attributes_.push_back (attributes {has, l, {}});
 
     if (!has)
       return make_pair (false, l);
@@ -3727,7 +3745,7 @@ namespace build2
         }
 
         if (!pre_parse_)
-          attributes_.top ().ats.emplace_back (move (n), move (v));
+          attributes_.back ().ats.emplace_back (move (n), move (v));
 
         if (tt == type::comma)
           next (t, tt);
@@ -5592,18 +5610,20 @@ namespace build2
   buildspec parser::
   parse_buildspec (istream& is, const path_name& in)
   {
-    path_ = &in;
-
     // We do "effective escaping" and only for ['"\$(] (basically what's
     // necessary inside a double-quoted literal plus the single quote).
     //
+    path_ = &in;
     lexer l (is, *path_, 1 /* line */, "\'\"\\$(");
     lexer_ = &l;
-    scope_ = root_ = &ctx.global_scope.rw ();
-    pbase_ = &work; // Use current working directory.
+
+    root_ = &ctx.global_scope.rw ();
+    scope_ = root_;
     target_ = nullptr;
     prerequisite_ = nullptr;
 
+    pbase_ = &work; // Use current working directory.
+
     // Turn on the buildspec mode/pairs recognition with '@' as the pair
     // separator (e.g., src_root/@out_root/exe{foo bar}).
     //
diff --git a/libbuild2/parser.hxx b/libbuild2/parser.hxx
index ba707da..6d78ce1 100644
--- a/libbuild2/parser.hxx
+++ b/libbuild2/parser.hxx
@@ -4,8 +4,6 @@
 #ifndef LIBBUILD2_PARSER_HXX
 #define LIBBUILD2_PARSER_HXX
 
-#include <stack>
-
 #include <libbuild2/types.hxx>
 #include <libbuild2/forward.hxx>
 #include <libbuild2/utility.hxx>
@@ -60,9 +58,22 @@ namespace build2
     parse_export_stub (istream& is, const path_name& name, scope& r, scope& b)
     {
       parse_buildfile (is, name, r, b);
-      return move (export_value_);
+      return move (export_value);
     }
 
+    // The above functions may be called again on the same parser instance
+    // after a reset.
+    //
+    void
+    reset ();
+
+    // Ad hoc parsing results for some cases.
+    //
+    // Note that these are not touched by reset().
+    //
+  public:
+    names export_value;
+
     // Recursive descent parser.
     //
   protected:
@@ -246,13 +257,13 @@ namespace build2
     attributes_pop ()
     {
       assert (!pre_parse_);
-      attributes r (move (attributes_.top ()));
-      attributes_.pop ();
+      attributes r (move (attributes_.back ()));
+      attributes_.pop_back ();
       return r;
     }
 
     attributes&
-    attributes_top () {return attributes_.top ();}
+    attributes_top () {return attributes_.back ();}
 
     // Source a stream optionnaly entering it as a buildfile and performing
     // the default target processing.
@@ -703,6 +714,10 @@ namespace build2
   protected:
     const fail_mark fail;
 
+    // Parser state.
+    //
+    // NOTE: remember to update reset() if adding anything here.
+    //
   protected:
     context& ctx;
     stage stage_;
@@ -719,10 +734,9 @@ namespace build2
 
     const dir_path* pbase_ = nullptr; // Current pattern base directory.
 
-    std::stack<attributes> attributes_;
+    small_vector<attributes, 2> attributes_;
 
-    target* default_target_;
-    names export_value_;
+    target* default_target_ = nullptr;
 
     replay_token peek_;
     bool peeked_ = false;
-- 
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