Implement rule chaining for cxx::link

1 files changed, 42 insertions, 0 deletions

diff --git a/build/prerequisite.cxx b/build/prerequisite.cxx
index 370f5d0..f5461ef 100644
--- a/build/prerequisite.cxx
+++ b/build/prerequisite.cxx
@@ -9,6 +9,7 @@
 #include <build/scope>
 #include <build/target> // target_type
 #include <build/context>
+#include <build/diagnostics>
 
 using namespace std;
 
@@ -72,4 +73,45 @@ namespace build
        x.directory == y.directory &&
        x.ext != nullptr && y.ext != nullptr && x.ext < y.ext);
   }
+
+  // prerequisite_set
+  //
+  auto prerequisite_set::
+  insert (const target_type& tt,
+          path dir,
+          std::string name,
+          const std::string* ext,
+          scope& s,
+          tracer& tr) -> pair<prerequisite&, bool>
+  {
+    //@@ OPT: would be nice to somehow first check if this prerequisite is
+    //   already in the set before allocating a new instance.
+
+    // Find or insert.
+    //
+    auto r (emplace (tt, move (dir), move (name), ext, s));
+    prerequisite& p (const_cast<prerequisite&> (*r.first));
+
+    // Update extension if the existing prerequisite has it unspecified.
+    //
+    if (p.ext != ext)
+    {
+      trace (4, [&]{
+          tracer::record r (tr);
+          r << "assuming prerequisite " << p << " 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)
+        p.ext = ext;
+    }
+
+    return pair<prerequisite&, bool> (p, r.second);
+  }
 }