Implement rule chaining for cxx::link

1 files changed, 44 insertions, 2 deletions

diff --git a/build/target.cxx b/build/target.cxx
index 61423db..b20f53b 100644
--- a/build/target.cxx
+++ b/build/target.cxx
@@ -4,9 +4,8 @@
 
 #include <build/target>
 
-#include <ostream>
-
 #include <build/context>
+#include <build/diagnostics>
 
 using namespace std;
 
@@ -37,7 +36,50 @@ namespace build
     return os;
   }
 
+  // target_set
+  //
+  auto target_set::
+  insert (const target_type& tt,
+          path dir,
+          std::string name,
+          const std::string* ext,
+          tracer& tr) -> pair<target&, bool>
+  {
+    //@@ OPT: would be nice to somehow first check if this target is
+    //   already in the set before allocating a new instance.
+
+    // Find or insert.
+    //
+    auto r (
+      emplace (
+        unique_ptr<target> (tt.factory (move (dir), move (name), ext))));
+
+    target& t (**r.first);
+
+    // Update the extension if the existing target has it unspecified.
+    //
+    if (t.ext != ext)
+    {
+      trace (4, [&]{
+          tracer::record r (tr);
+          r << "assuming target " << t << " is the same as the one with ";
+          if (ext == nullptr)
+            r << "unspecified extension";
+          else if (ext->empty ())
+            r << "no extension";
+          else
+            r << "extension " << *ext;
+        });
+
+      if (ext != nullptr)
+        t.ext = ext;
+    }
+
+    return pair<target&, bool> (t, r.second);
+  }
+
   target_set targets;
+
   target* default_target = nullptr;
   target_type_map target_types;