From ce8a94e6a76097ef7eeb34df4257991a20599712 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Wed, 14 Jan 2015 11:39:21 +0200
Subject: Track file extension in target, prerequisite

---
 build/trace | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

(limited to 'build/trace')

diff --git a/build/trace b/build/trace
index f1c0567..1764a69 100644
--- a/build/trace
+++ b/build/trace
@@ -34,9 +34,11 @@ namespace build
         return std::cerr << x;
       }
 
+      explicit record (tracer& t): empty_ (false) {t.begin ();}
+      explicit record (bool e = true): empty_ (e) {}
+
       // Movable-only type.
       //
-      explicit record (bool e = true): empty_ (e) {}
       record (record&& r) {empty_ = r.empty_; r.empty_ = true;}
       record& operator= (record&& r) {empty_ = r.empty_; r.empty_ = true;}
 
@@ -51,10 +53,17 @@ namespace build
     record
     operator<< (const T& x) const
     {
-      std::cerr << "trace: " << name_ << ": " << x;
+      begin ();
+      std::cerr << x;
       return record (false);
     }
 
+    void
+    begin () const
+    {
+      std::cerr << "trace: " << name_ << ": ";
+    }
+
   private:
     const char* name_;
   };
-- 
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