From fa6f9986dd73627643469c238b32dd92607f5214 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Mon, 9 Mar 2015 09:45:25 +0200
Subject: Add support for skipping already loaded/included buildfiles at top
 level

The idea is that a buildfile shall be included/loaded only once for any
given out_root.
---
 build/b.cxx      | 14 ++++++++++++--
 build/lexer      |  4 ++--
 build/parser     |  8 +++-----
 build/parser.cxx | 13 +++++++------
 build/scope      |  8 ++++++++
 5 files changed, 32 insertions(+), 15 deletions(-)

diff --git a/build/b.cxx b/build/b.cxx
index 0a1d8d2..ce10b22 100644
--- a/build/b.cxx
+++ b/build/b.cxx
@@ -269,7 +269,7 @@ main (int argc, char* argv[])
 
           if (verb >= 4)
           {
-            trace << tn;
+            trace << tn << ':';
             trace << "  out_base: " << out_base.string ();
             trace << "  src_base: " << src_base.string ();
             trace << "  out_root: " << out_root.string ();
@@ -293,6 +293,16 @@ main (int argc, char* argv[])
           //
           path bf (src_base / path ("buildfile"));
 
+          // Check if this buildfile has already been loaded.
+          //
+          if (!proot_scope.buildfiles.insert (bf).second)
+          {
+            level4 ([&]{trace << "skipping already loaded " << bf;});
+            continue;
+          }
+
+          level4 ([&]{trace << "loading " << bf;});
+
           ifstream ifs (bf.string ());
           if (!ifs.is_open ())
             fail << "unable to open " << bf;
@@ -302,7 +312,7 @@ main (int argc, char* argv[])
 
           try
           {
-            p.parse_buildfile (ifs, bf, pbase_scope);
+            p.parse_buildfile (ifs, bf, pbase_scope, proot_scope);
           }
           catch (const std::ios_base::failure&)
           {
diff --git a/build/lexer b/build/lexer
index 787ba72..98a1390 100644
--- a/build/lexer
+++ b/build/lexer
@@ -127,8 +127,8 @@ namespace build
 
     bool eos_ {false};
     lexer_mode mode_ {lexer_mode::normal};
-    lexer_mode next_mode_; // Mode to switch to for the next token.
-    lexer_mode prev_mode_; // Mode to return to after this mode expires.
+    lexer_mode next_mode_ {lexer_mode::normal}; // Switch to for next token.
+    lexer_mode prev_mode_; // Return to after current mode expires.
   };
 }
 
diff --git a/build/parser b/build/parser
index 25866bc..50e306d 100644
--- a/build/parser
+++ b/build/parser
@@ -7,7 +7,6 @@
 
 #include <string>
 #include <iosfwd>
-#include <unordered_set>
 
 #include <build/path>
 #include <build/token>
@@ -29,7 +28,7 @@ namespace build
     // Issue diagnostics and throw failed in case of an error.
     //
     void
-    parse_buildfile (std::istream&, const path&, scope&);
+    parse_buildfile (std::istream&, const path&, scope& base, scope& root);
 
     buildspec
     parse_buildspec (std::istream&, const std::string& name);
@@ -99,7 +98,8 @@ namespace build
   private:
     const std::string* path_; // Path processed by diagnostic_string().
     lexer* lexer_;
-    scope* scope_;
+    scope* scope_; // Current base scope (out_base).
+    scope* root_;  // Current root scope (out_root).
     target* default_target_;
 
     const path* out_root_;
@@ -107,8 +107,6 @@ namespace build
 
     token peek_ {token_type::eos, false, 0, 0};
     bool peeked_ {false};
-
-    std::unordered_set<path> include_;
   };
 }
 
diff --git a/build/parser.cxx b/build/parser.cxx
index 2c629d6..343f5e1 100644
--- a/build/parser.cxx
+++ b/build/parser.cxx
@@ -37,18 +37,19 @@ namespace build
   typedef token_type type;
 
   void parser::
-  parse_buildfile (istream& is, const path& p, scope& s)
+  parse_buildfile (istream& is, const path& p, scope& base, scope& root)
   {
     string rw (diag_relative_work (p));
     path_ = &rw;
 
     lexer l (is, rw);
     lexer_ = &l;
-    scope_ = &s;
+    scope_ = &base;
+    root_ = &root;
     default_target_ = nullptr;
 
-    out_root_ = &s["out_root"].as<const path&> ();
-    src_root_ = &s["src_root"].as<const path&> ();
+    out_root_ = &root["out_root"].as<const path&> ();
+    src_root_ = &root["src_root"].as<const path&> ();
 
     token t (type::eos, false, 0, 0);
     type tt;
@@ -477,7 +478,7 @@ namespace build
         p.normalize ();
       }
 
-      if (!include_.insert (p).second)
+      if (!root_->buildfiles.insert (p).second)
       {
         level4 ([&]{trace (l) << "skipping already included " << p;});
         continue;
@@ -955,7 +956,7 @@ namespace build
 
     lexer l (is, name);
     lexer_ = &l;
-    scope_ = root_scope;
+    scope_ = root_ = root_scope;
 
     // Turn on pairs recognition (e.g., src_root/=out_root/exe{foo bar}).
     //
diff --git a/build/scope b/build/scope
index b4f492d..e5c5fec 100644
--- a/build/scope
+++ b/build/scope
@@ -5,6 +5,8 @@
 #ifndef BUILD_SCOPE
 #define BUILD_SCOPE
 
+#include <unordered_set>
+
 #include <build/path>
 #include <build/path-map>
 #include <build/variable>
@@ -49,6 +51,12 @@ namespace build
     variable_map variables;
     prerequisite_set prerequisites;
 
+    // Set of buildfiles already loaded for this scope. The included
+    // buildfiles are checked against project root scope while
+    // imported -- against the overall root scope (root_scope).
+    //
+    std::unordered_set<path_type> buildfiles;
+
   private:
     iterator i_;
     scope* parent_;
-- 
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