From f11d720f2fb62b46ad17d3aa3850140a4839f114 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Wed, 13 Dec 2017 14:20:54 +0200
Subject: Implement info meta operation

This meta operation can be used to print basic information (name, version,
source/output roots, etc) for one or more projects.
---
 build2/variable.hxx | 12 ++++++++++++
 1 file changed, 12 insertions(+)

(limited to 'build2/variable.hxx')

diff --git a/build2/variable.hxx b/build2/variable.hxx
index bba2208..51cc350 100644
--- a/build2/variable.hxx
+++ b/build2/variable.hxx
@@ -546,6 +546,14 @@ namespace build2
   static int
   simple_compare (const value&, const value&);
 
+  // names
+  //
+  template <>
+  struct value_traits<names>
+  {
+    static const names& empty_instance;
+  };
+
   // bool
   //
   template <>
@@ -783,6 +791,8 @@ namespace build2
     static void prepend (value&, vector<T>&&);
     static bool empty (const vector<T>& x) {return x.empty ();}
 
+    static const vector<T> empty_instance;
+
     // Make sure these are static-initialized together. Failed that VC will
     // make sure it's done in the wrong order.
     //
@@ -809,6 +819,8 @@ namespace build2
       return append (v, move (x));}
     static bool empty (const map<K, V>& x) {return x.empty ();}
 
+    static const map<K, V> empty_instance;
+
     // Make sure these are static-initialized together. Failed that VC will
     // make sure it's done in the wrong order.
     //
-- 
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