From 8345d5eba80a11de363c8a96070316fdd6b6fd22 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 14 Jan 2021 14:31:27 +0200
Subject: Pass /Zc:__cplusplus by default starting from VC 15.7 (GitHub issue
 #107)

This can be overridden by passing a variant of this option as part of the
compiler mode options.
---
 libbuild2/cxx/init.cxx | 11 +++++++++++
 1 file changed, 11 insertions(+)

(limited to 'libbuild2/cxx')

diff --git a/libbuild2/cxx/init.cxx b/libbuild2/cxx/init.cxx
index ad0dd05..e2d7343 100644
--- a/libbuild2/cxx/init.cxx
+++ b/libbuild2/cxx/init.cxx
@@ -189,6 +189,17 @@ namespace build2
           if (!o.empty ())
             prepend (move (o));
 
+          // Since VC 15.7 we can get a (more) accurate __cplusplus value if
+          // we ask for it with /Zc:__cplusplus:
+          //
+          // https://devblogs.microsoft.com/cppblog/msvc-now-correctly-reports-__cplusplus/
+          //
+          if (mj > 19 || (mj == 19 &&  mi >= 14))
+          {
+            if (!find_option_prefix ("/Zc:__cplusplus", mode))
+              prepend ("/Zc:__cplusplus");
+          }
+
           break;
         }
       case compiler_class::gcc:
-- 
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