From 4fe1c3c083acecf7eabe46b67cb540e8390f3122 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Tue, 5 Nov 2019 11:34:47 +0200
Subject: Add support for supplying MSVC IFCPATH equivalent

---
 libbuild2/cc/compile-rule.cxx | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

(limited to 'libbuild2/cc/compile-rule.cxx')

diff --git a/libbuild2/cc/compile-rule.cxx b/libbuild2/cc/compile-rule.cxx
index c0f876c..98b78e1 100644
--- a/libbuild2/cc/compile-rule.cxx
+++ b/libbuild2/cc/compile-rule.cxx
@@ -5576,11 +5576,24 @@ namespace build2
       for (const string& a: stor)
         args.push_back (a.c_str ());
 
-      // VC's IFCPATH takes precedence over /module:stdIfcDir so unset it
-      // if we are using our own std modules.
-      //
-      if (!stdifc.empty ())
-        env.push_back ("IFCPATH");
+      if (getenv ("IFCPATH"))
+      {
+        // VC's IFCPATH takes precedence over /module:stdIfcDir so unset it if
+        // we are using our own std modules.
+        //
+        if (!stdifc.empty ())
+          env.push_back ("IFCPATH");
+      }
+      else if (stdifc.empty ())
+      {
+        // Add the VC's default directory (should be only one).
+        //
+        if (sys_mod_dirs && !sys_mod_dirs->empty ())
+        {
+          args.push_back ("/module:stdIfcDir");
+          args.push_back (sys_mod_dirs->front ().string ().c_str ());
+        }
+      }
     }
 
     target_state compile_rule::
-- 
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