Diagnose lack of module support in extract_modules()

4 files changed, 20 insertions, 5 deletions

diff --git a/build2/c/init.cxx b/build2/c/init.cxx
index 30c324a..b4b2bca 100644
--- a/build2/c/init.cxx
+++ b/build2/c/init.cxx
@@ -262,6 +262,8 @@ namespace build2
 
         cm.tstd,
 
+        false, // No C modules for now.
+
         cast_null<process_path> (rs["pkgconfig.path"]),
         cast<dir_paths>         (rs[cm.x_sys_lib_dirs]),
         cast<dir_paths>         (rs[cm.x_sys_inc_dirs]),
diff --git a/build2/cc/common.hxx b/build2/cc/common.hxx
index fa6ec5a..155d670 100644
--- a/build2/cc/common.hxx
+++ b/build2/cc/common.hxx
@@ -114,6 +114,8 @@ namespace build2
 
       const strings& tstd;         // Translated x_std value (options).
 
+      bool modules;                // x.feaures.modules
+
       const process_path* pkgconfig; // pkgconfig.path (can be NULL).
       const dir_paths& sys_lib_dirs; // x.sys_lib_dirs
       const dir_paths& sys_inc_dirs; // x.sys_inc_dirs
@@ -154,6 +156,7 @@ namespace build2
             const process_path& path,
             const target_triplet& tg,
             const strings& std,
+            bool mod,
             const process_path* pkgc,
             const dir_paths& sld,
             const dir_paths& sid,
@@ -168,6 +171,7 @@ namespace build2
             cid (id), cvar (var), cmaj (mj), cmin (mi), cpath (path),
             ctg (tg), tsys (ctg.system), tclass (ctg.class_),
             tstd (std),
+            modules (mod),
             pkgconfig (pkgc), sys_lib_dirs (sld), sys_inc_dirs (sid),
             x_src (src), x_hdr (hdr), x_inc (inc) {}
     };
diff --git a/build2/cc/compile.cxx b/build2/cc/compile.cxx
index ce96e00..c7fc3ea 100644
--- a/build2/cc/compile.cxx
+++ b/build2/cc/compile.cxx
@@ -610,9 +610,8 @@ namespace build2
 
         dd.close ();
 
-        // If C++ modules support is enabled then we need to extract the
-        // module dependency information in addition to header dependencies
-        // above.
+        // Extract the module dependency information in addition to header
+        // dependencies above.
         //
         if (u) // @@ TMP (depdb validation similar to extract_headers()).
         {
@@ -2207,8 +2206,16 @@ namespace build2
         throw failed ();
       }
 
-      if (!tu.module_name.empty () || !tu.module_imports.empty ())
-        fail << "module support not yet implemented";
+      //@@ TODO: if bmi{}, make sure module_name is not empty.
+
+      if (tu.module_name.empty () && tu.module_imports.empty ())
+        return;
+
+      // Modules are used by this translation unit. Make sure module support
+      // is enabled.
+      //
+      if (!modules)
+        fail << "modules support not enabled or unavailable";
     }
 
     // Filter cl.exe noise (msvc.cxx).
diff --git a/build2/cxx/init.cxx b/build2/cxx/init.cxx
index f6162ab..fde12e3 100644
--- a/build2/cxx/init.cxx
+++ b/build2/cxx/init.cxx
@@ -433,6 +433,8 @@ namespace build2
 
         cm.tstd,
 
+        cast<bool> (rs["cxx.features.modules"]),
+
         cast_null<process_path> (rs["pkgconfig.path"]),
         cast<dir_paths> (rs[cm.x_sys_lib_dirs]),
         cast<dir_paths> (rs[cm.x_sys_inc_dirs]),