From a14b9bc18431c6aed8441261d28b6ff20bd25935 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 11 Apr 2019 14:44:32 +0200
Subject: Initial take on header unit and include translation support

---
 build2/cxx/init.cxx | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

(limited to 'build2/cxx')

diff --git a/build2/cxx/init.cxx b/build2/cxx/init.cxx
index aca1fb8..adb1d92 100644
--- a/build2/cxx/init.cxx
+++ b/build2/cxx/init.cxx
@@ -387,14 +387,26 @@ namespace build2
         v.insert<strings> ("config.cxx.loptions", true),
         v.insert<strings> ("config.cxx.libs",     true),
 
+        // List of modular headers. Inclusion of such headers is translated to
+        // the corresponding header unit imports.
+        //
+        // A header can be specified either as an absolute and normalized path
+        // or as a <>-style include name. The latter kind is automatically
+        // translated to the absolute form based on the include search paths
+        // extracted from the compiler. Note also that all entries must be
+        // specified before loading the module.
+        //
+        &v.insert<strings> ("config.cxx.header_units", true),
+
         v.insert<process_path> ("cxx.path"),
         v.insert<dir_paths>    ("cxx.sys_lib_dirs"),
         v.insert<dir_paths>    ("cxx.sys_inc_dirs"),
 
-        v.insert<strings> ("cxx.poptions"),
-        v.insert<strings> ("cxx.coptions"),
-        v.insert<strings> ("cxx.loptions"),
-        v.insert<strings> ("cxx.libs"),
+        v.insert<strings>  ("cxx.poptions"),
+        v.insert<strings>  ("cxx.coptions"),
+        v.insert<strings>  ("cxx.loptions"),
+        v.insert<strings>  ("cxx.libs"),
+        &v.insert<strings> ("cxx.header_units"),
 
         v["cc.poptions"],
         v["cc.coptions"],
@@ -430,6 +442,9 @@ namespace build2
         // for some compilers (e.g., VC) there is no way to signal that the
         // source is already preprocessed.
         //
+        // What about header unit imports? Well, they are in a sense
+        // standardized precompiled headers so we treat them as includes.
+        //
         v.insert<string>   ("cxx.preprocessed"),
 
         nullptr, // cxx.features.symexport (set in init() below).
-- 
cgit v1.1