From 9c4ce4464b2a0dae55b7cfb2ec5fc4bd7ffc40ae Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Wed, 2 Sep 2015 17:11:50 +0200
Subject: Override duplicate generated C++ dependency prefix

---
 build/cxx/compile.cxx | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

(limited to 'build')

diff --git a/build/cxx/compile.cxx b/build/cxx/compile.cxx
index f9351f2..9a3e3d7 100644
--- a/build/cxx/compile.cxx
+++ b/build/cxx/compile.cxx
@@ -263,9 +263,18 @@ namespace build
           if (j != m.end ())
           {
             if (j->second != d)
-              fail << "duplicate generated dependency prefix '" << p << "'" <<
-                info << "old mapping to " << j->second <<
-                info << "new mapping to " << d;
+            {
+              // We used to reject duplicates but it seems this can
+              // be reasonably expected to work according to the order
+              // of the -I options.
+              //
+              if (verb >= 3)
+                trace << "overriding dependency prefix '" << p << "'\n"
+                      << "  old mapping to " << j->second << "\n"
+                      << "  new mapping to " << d;
+
+              j->second = d;
+            }
           }
           else
           {
-- 
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