From 43c53a8b475f901a902ba1bf6ec603e7a28311b1 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Fri, 3 May 2019 09:18:09 +0200
Subject: Adjust modules support enablement for GCC

Now we require c++-modules-ex branch unless forced.
---
 build2/cxx/init.cxx | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

(limited to 'build2')

diff --git a/build2/cxx/init.cxx b/build2/cxx/init.cxx
index adb1d92..3fb636f 100644
--- a/build2/cxx/init.cxx
+++ b/build2/cxx/init.cxx
@@ -293,11 +293,15 @@ namespace build2
             }
           case compiler_type::gcc:
             {
-              // Enable starting with GCC 9.0.0 (currently the c++-modules
-              // branch).
+              // We now use extended/experimental module mapper support which
+              // is currently only available in our c++-modules-ex branch.
+              // But let's allow forcing it to plain c++-modules in case
+              // things got merged, etc.
               //
-              if (mj >= 9 &&
-                  ci.version.build.find ("c++-modules") != string::npos)
+              if (mj >= 10 &&
+                  ci.version.build.find (l
+                                         ? "c++-modules"
+                                         : "c++-modules-ex") != string::npos)
               {
                 // Currently defines __cpp_modules=201810 which is said to
                 // correspond to p1103 (merged modules).
@@ -316,6 +320,9 @@ namespace build2
               //
               // Also see Clang modules support hack in cc::compile.
               //
+              // @@ Clang 9 enables modules by default in C++2a. We should
+              //    probably reflect this in the modules value.
+              //
               if (mj >= 6)
               {
                 r.push_back ("-D__cpp_modules=201704"); // p0629r0
-- 
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