Add support for passing configuration hints via module init()

17 files changed, 97 insertions, 28 deletions

diff --git a/build2/bin/module b/build2/bin/module
index 44dfbc7..0b9d44e 100644
--- a/build2/bin/module
+++ b/build2/bin/module
@@ -15,8 +15,13 @@ namespace build2
   namespace bin
   {
     extern "C" bool
-    bin_init (
-      scope&, scope&, const location&, unique_ptr<module_base>&, bool, bool);
+    bin_init (scope&,
+              scope&,
+              const location&,
+              unique_ptr<module_base>&,
+              bool,
+              bool,
+              const variable_map&);
   }
 }
 
diff --git a/build2/bin/module.cxx b/build2/bin/module.cxx
index 1ab29f9..d5df054 100644
--- a/build2/bin/module.cxx
+++ b/build2/bin/module.cxx
@@ -36,11 +36,14 @@ namespace build2
               const location&,
               unique_ptr<module_base>&,
               bool first,
-              bool)
+              bool,
+              const variable_map& config_hints)
     {
       tracer trace ("bin::init");
       l5 ([&]{trace << "for " << b.out_path ();});
 
+      assert (config_hints.empty ()); // We don't known any hints.
+
       // Enter module variables.
       //
       if (first)
diff --git a/build2/cli/module b/build2/cli/module
index 0469b2c..f55e03c 100644
--- a/build2/cli/module
+++ b/build2/cli/module
@@ -15,8 +15,13 @@ namespace build2
   namespace cli
   {
     extern "C" bool
-    cli_init (
-    scope&, scope&, const location&, unique_ptr<module_base>&, bool, bool);
+    cli_init (scope&,
+              scope&,
+              const location&,
+              unique_ptr<module_base>&,
+              bool,
+              bool,
+              const variable_map&);
   }
 }
 
diff --git a/build2/cli/module.cxx b/build2/cli/module.cxx
index 478c8a8..13325d9 100644
--- a/build2/cli/module.cxx
+++ b/build2/cli/module.cxx
@@ -31,11 +31,14 @@ namespace build2
               const location& loc,
               unique_ptr<module_base>&,
               bool first,
-              bool optional)
+              bool optional,
+              const variable_map& config_hints)
     {
       tracer trace ("cli::init");
       l5 ([&]{trace << "for " << base.out_path ();});
 
+      assert (config_hints.empty ()); // We don't known any hints.
+
       // Make sure the cxx module has been loaded since we need its targets
       // types (?xx{}). Note that we don't try to load it ourselves because of
       // the non-trivial variable merging semantics. So it is better to let
diff --git a/build2/config/module b/build2/config/module
index 6012442..912ab57 100644
--- a/build2/config/module
+++ b/build2/config/module
@@ -32,8 +32,13 @@ namespace build2
     config_boot (scope&, const location&, unique_ptr<module_base>&);
 
     extern "C" bool
-    config_init (
-      scope&, scope&, const location&, unique_ptr<module_base>&, bool, bool);
+    config_init (scope&,
+                 scope&,
+                 const location&,
+                 unique_ptr<module_base>&,
+                 bool,
+                 bool,
+                 const variable_map&);
   }
 }
 
diff --git a/build2/config/module.cxx b/build2/config/module.cxx
index 16eabe9..70301c5 100644
--- a/build2/config/module.cxx
+++ b/build2/config/module.cxx
@@ -59,7 +59,8 @@ namespace build2
                  const location& l,
                  unique_ptr<module_base>& mod,
                  bool first,
-                 bool)
+                 bool,
+                 const variable_map& config_hints)
     {
       tracer trace ("config::init");
 
@@ -71,6 +72,8 @@ namespace build2
 
       l5 ([&]{trace << "for " << root.out_path ();});
 
+      assert (config_hints.empty ()); // We don't known any hints.
+
       // Only create the module if we are configuring.
       //
       if (current_mif->id == configure_id)
diff --git a/build2/cxx/module b/build2/cxx/module
index 39d1218..254eb44 100644
--- a/build2/cxx/module
+++ b/build2/cxx/module
@@ -15,8 +15,13 @@ namespace build2
   namespace cxx
   {
     extern "C" bool
-    cxx_init (
-      scope&, scope&, const location&, unique_ptr<module_base>&, bool, bool);
+    cxx_init (scope&,
+              scope&,
+              const location&,
+              unique_ptr<module_base>&,
+              bool,
+              bool,
+              const variable_map&);
   }
 }
 
diff --git a/build2/cxx/module.cxx b/build2/cxx/module.cxx
index c03763f..7e9b5e2 100644
--- a/build2/cxx/module.cxx
+++ b/build2/cxx/module.cxx
@@ -35,11 +35,14 @@ namespace build2
               const location& loc,
               unique_ptr<module_base>&,
               bool first,
-              bool)
+              bool,
+              const variable_map& config_hints)
     {
       tracer trace ("cxx::init");
       l5 ([&]{trace << "for " << b.out_path ();});
 
+      assert (config_hints.empty ()); // We don't known any hints.
+
       // Initialize the bin module. Only do this if it hasn't already been
       // loaded so that we don't overwrite user's bin.* settings.
       //
diff --git a/build2/dist/module b/build2/dist/module
index 61e44c3..984a969 100644
--- a/build2/dist/module
+++ b/build2/dist/module
@@ -18,8 +18,13 @@ namespace build2
     dist_boot (scope&, const location&, unique_ptr<module_base>&);
 
     extern "C" bool
-    dist_init (
-      scope&, scope&, const location&, unique_ptr<module_base>&, bool, bool);
+    dist_init (scope&,
+               scope&,
+               const location&,
+               unique_ptr<module_base>&,
+               bool,
+               bool,
+               const variable_map&);
   }
 }
 
diff --git a/build2/dist/module.cxx b/build2/dist/module.cxx
index 5ae05a4..58bfc6f 100644
--- a/build2/dist/module.cxx
+++ b/build2/dist/module.cxx
@@ -60,7 +60,8 @@ namespace build2
                const location& l,
                unique_ptr<module_base>&,
                bool first,
-               bool)
+               bool,
+               const variable_map& config_hints)
     {
       tracer trace ("dist::init");
 
@@ -73,6 +74,8 @@ namespace build2
       const dir_path& out_root (r.out_path ());
       l5 ([&]{trace << "for " << out_root;});
 
+      assert (config_hints.empty ()); // We don't known any hints.
+
       // Register our wildcard rule. Do it explicitly for the alias
       // to prevent something like insert<target>(dist_id, test_id)
       // taking precedence.
diff --git a/build2/install/module b/build2/install/module
index f81b6ac..b2a3301 100644
--- a/build2/install/module
+++ b/build2/install/module
@@ -18,8 +18,13 @@ namespace build2
     install_boot (scope&, const location&, unique_ptr<module_base>&);
 
     extern "C" bool
-    install_init (
-      scope&, scope&, const location&, unique_ptr<module_base>&, bool, bool);
+    install_init (scope&,
+                  scope&,
+                  const location&,
+                  unique_ptr<module_base>&,
+                  bool,
+                  bool,
+                  const variable_map&);
   }
 }
 
diff --git a/build2/install/module.cxx b/build2/install/module.cxx
index 15c6ea8..6a7e500 100644
--- a/build2/install/module.cxx
+++ b/build2/install/module.cxx
@@ -118,7 +118,8 @@ namespace build2
                   const location& l,
                   unique_ptr<module_base>&,
                   bool first,
-                  bool)
+                  bool,
+                  const variable_map& config_hints)
     {
       tracer trace ("install::init");
 
@@ -131,6 +132,8 @@ namespace build2
       const dir_path& out_root (r.out_path ());
       l5 ([&]{trace << "for " << out_root;});
 
+      assert (config_hints.empty ()); // We don't known any hints.
+
       // Enter module variables.
       //
       // Note that the set_dir() calls below enter some more.
diff --git a/build2/module b/build2/module
index dcfe5d0..314f5a6 100644
--- a/build2/module
+++ b/build2/module
@@ -10,6 +10,7 @@
 #include <build2/types>
 #include <build2/utility>
 
+#include <build2/variable>
 #include <build2/diagnostics>
 
 namespace build2
@@ -40,8 +41,9 @@ namespace build2
           scope& base,
           const location&,
           unique_ptr<module_base>&,
-          bool first,     // First time for this project.
-          bool optional); // Loaded with 'using?' (optional module).
+          bool first,                 // First time for this project.
+          bool optional,              // Loaded with using? (optional module).
+          const variable_map& hints); // Configuration hints (see below).
 
 
   struct module_state
@@ -75,12 +77,19 @@ namespace build2
   // Return true if the module was both successfully loaded and configured
   // (false can only be returned if optional).
   //
+  // The config_hints variable map can be used to pass configuration hints
+  // from one module to another. For example, the cxx modude may pass the
+  // target platform (which was extracted from the C++ compiler) to the bin
+  // module (which may not always be able to extract the same information from
+  // its tools).
+  //
   bool
   load_module (const string& name,
                scope& root,
                scope& base,
                const location&,
-               bool optional = false);
+               bool optional = false,
+               const variable_map& config_hints = variable_map ());
 
   // Builtin modules.
   //
diff --git a/build2/module.cxx b/build2/module.cxx
index 1334689..e1e8afd 100644
--- a/build2/module.cxx
+++ b/build2/module.cxx
@@ -54,7 +54,8 @@ namespace build2
                scope& rs,
                scope& bs,
                const location& loc,
-               bool opt)
+               bool opt,
+               const variable_map& hints)
   {
     // First see if this modules has already been loaded for this project.
     //
@@ -96,7 +97,8 @@ namespace build2
     }
 
     bool l (i != lm.end ());
-    bool c (l && i->second.init (rs, bs, loc, i->second.module, f, opt));
+    bool c (l &&
+            i->second.init (rs, bs, loc, i->second.module, f, opt, hints));
 
     const variable& lv (var_pool.insert<bool> (name + ".loaded",
                                                false,
diff --git a/build2/test/module b/build2/test/module
index 756b4f6..b9c3ea5 100644
--- a/build2/test/module
+++ b/build2/test/module
@@ -18,8 +18,13 @@ namespace build2
     test_boot (scope&, const location&, unique_ptr<module_base>&);
 
     extern "C" bool
-    test_init (
-      scope&, scope&, const location&, unique_ptr<module_base>&, bool, bool);
+    test_init (scope&,
+               scope&,
+               const location&,
+               unique_ptr<module_base>&,
+               bool,
+               bool,
+               const variable_map&);
   }
 }
 
diff --git a/build2/test/module.cxx b/build2/test/module.cxx
index e5b044a..c20e274 100644
--- a/build2/test/module.cxx
+++ b/build2/test/module.cxx
@@ -55,7 +55,8 @@ namespace build2
                const location& l,
                unique_ptr<module_base>&,
                bool first,
-               bool)
+               bool,
+               const variable_map& config_hints)
     {
       tracer trace ("test::init");
 
@@ -68,7 +69,10 @@ namespace build2
       const dir_path& out_root (root.out_path ());
       l5 ([&]{trace << "for " << out_root;});
 
-      //@@ Need ability to specify extra diff options (--strip-trailing-cr).
+      assert (config_hints.empty ()); // We don't known any hints.
+
+      //@@ TODO: Need ability to specify extra diff options (e.g.,
+      //   --strip-trailing-cr, now hardcoded).
 
       // Register rules.
       //
diff --git a/build2/variable b/build2/variable
index c506a3e..5c567da 100644
--- a/build2/variable
+++ b/build2/variable
@@ -663,8 +663,9 @@ namespace build2
 
   // variable_map
   //
-  struct variable_map
+  class variable_map
   {
+  public:
     using map_type = butl::prefix_map<variable_cref, value, '.'>;
     using size_type = map_type::size_type;