From 97913b6fb268f327ee1a689779cb9b0621f72ff2 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Fri, 29 Jul 2016 09:19:37 +0200
Subject: Fix duplicate config.build variable issue

---
 build2/config/module        | 18 +++++++++++++++++-
 build2/config/operation.cxx | 11 +++--------
 build2/config/utility.cxx   | 11 +++++++++--
 3 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/build2/config/module b/build2/config/module
index 5becfd4..7360cf6 100644
--- a/build2/config/module
+++ b/build2/config/module
@@ -5,6 +5,8 @@
 #ifndef BUILD2_CONFIG_MODULE
 #define BUILD2_CONFIG_MODULE
 
+#include <algorithm> // find_if()
+
 #include <butl/prefix-map>
 
 #include <build2/types>
@@ -29,7 +31,21 @@ namespace build2
       uint64_t flags;
     };
 
-    using saved_variables = vector<saved_variable>;
+    struct saved_variables: vector<saved_variable>
+    {
+      // Normally each module only have a handful of config variables and we
+      // only do this during configuration so for now we do linear search
+      // instead of adding a map.
+      //
+      const_iterator
+      find (const variable& var) const
+      {
+        return std::find_if (
+          begin (),
+          end (),
+          [&var] (const saved_variable& v) {return var == v.var;});
+      }
+    };
 
     struct saved_modules: butl::prefix_map<string, saved_variables, '.'>
     {
diff --git a/build2/config/operation.cxx b/build2/config/operation.cxx
index faeb570..0773f00 100644
--- a/build2/config/operation.cxx
+++ b/build2/config/operation.cxx
@@ -143,7 +143,7 @@ namespace build2
               {
                 if (l.belongs (*r))
                 {
-                  // Find config module.
+                  // Find the config module.
                   //
                   if (auto* m = r->modules.lookup<const module> (module::name))
                   {
@@ -153,15 +153,10 @@ namespace build2
 
                     if (i != m->saved_modules.end ())
                     {
-                      // Find the variable. For now we do linear search.
+                      // Find the variable.
                       //
                       const saved_variables& sv (i->second);
-
-                      found = find_if (
-                        sv.begin (),
-                        sv.end (),
-                        [&var] (const saved_variable& v) {
-                          return var == v.var;}) != sv.end ();
+                      found = sv.find (var) != sv.end ();
 
                       // Handle that other case: if this is an override but
                       // the outer project itself is not being configured,
diff --git a/build2/config/utility.cxx b/build2/config/utility.cxx
index a24f7b3..b73e852 100644
--- a/build2/config/utility.cxx
+++ b/build2/config/utility.cxx
@@ -158,9 +158,16 @@ namespace build2
           i = sm.insert (string (n, 0, n.find ('.', 7)));
         }
 
-        // We assume each variable is saved/configured once.
+        // Don't insert duplicates. The config.import vars are particularly
+        // susceptible to duplication.
         //
-        i->second.push_back (saved_variable {var, flags});
+        saved_variables& sv (i->second);
+        auto j (sv.find (var));
+
+        if (j == sv.end ())
+          sv.push_back (saved_variable {var, flags});
+        else
+          assert (j->flags == flags);
       }
     }
   }
-- 
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