From f079a626a03d4a6e7be1031ddb2e971c8b9a9a75 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Wed, 6 Apr 2016 07:43:51 +0200
Subject: Fix NULL variable value assignment bug

---
 build2/variable.cxx | 46 ++++++++++++++++++++++++++++------------------
 1 file changed, 28 insertions(+), 18 deletions(-)

diff --git a/build2/variable.cxx b/build2/variable.cxx
index a8e3c77..da7446d 100644
--- a/build2/variable.cxx
+++ b/build2/variable.cxx
@@ -73,19 +73,24 @@ namespace build2
       // Now our types are the same. If the receiving value is NULL, then call
       // copy_ctor() instead of copy_assign().
       //
-      if (type == nullptr)
+      if (!v.null ())
       {
-        if (null ())
-          new (&data_) names (move (v).as<names> ());
+        if (type == nullptr)
+        {
+          if (null ())
+            new (&data_) names (move (v).as<names> ());
+          else
+            as<names> () = move (v).as<names> ();
+        }
+        else if (auto f = null () ? type->copy_ctor : type->copy_assign)
+          f (*this, v, true);
         else
-          as<names> () = move (v).as<names> ();
+          data_ = v.data_; // Assign as POD.
+
+        state = v.state;
       }
-      else if (auto f = null () ? type->copy_ctor : type->copy_assign)
-        f (*this, v, true);
       else
-        data_ = v.data_; // Assign as POD.
-
-      state = v.state;
+        *this = nullptr;
     }
 
     return *this;
@@ -109,19 +114,24 @@ namespace build2
       // Now our types are the same. If the receiving value is NULL, then call
       // copy_ctor() instead of copy_assign().
       //
-      if (type == nullptr)
+      if (!v.null ())
       {
-        if (null ())
-          new (&data_) names (v.as<names> ());
+        if (type == nullptr)
+        {
+          if (null ())
+            new (&data_) names (v.as<names> ());
+          else
+            as<names> () = v.as<names> ();
+        }
+        else if (auto f = null () ? type->copy_ctor : type->copy_assign)
+          f (*this, v, false);
         else
-          as<names> () = v.as<names> ();
+          data_ = v.data_; // Assign as POD.
+
+        state = v.state;
       }
-      else if (auto f = null () ? type->copy_ctor : type->copy_assign)
-        f (*this, v, false);
       else
-        data_ = v.data_; // Assign as POD.
-
-      state = v.state;
+        *this = nullptr;
     }
 
     return *this;
-- 
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