From bc6e269d1221f27d239044b376cc2c6e36dd1428 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Tue, 16 Jun 2015 09:20:40 +0200
Subject: Diagnose forward use of composite object ids

---
 odb/context.cxx   | 17 +++++++++++++++++
 odb/context.hxx   |  8 ++++++++
 odb/include.cxx   |  2 ++
 odb/validator.cxx | 32 +++++++++++++++++++++++++++++++-
 4 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/odb/context.cxx b/odb/context.cxx
index e6e50b8..726495f 100644
--- a/odb/context.cxx
+++ b/odb/context.cxx
@@ -1091,6 +1091,23 @@ class_file (semantics::class_& c)
     return c.file ();
 }
 
+location_t context::
+class_location (semantics::class_& c)
+{
+  if (c.count ("definition"))
+  {
+    return c.get<location_t> ("definition");
+  }
+  else if (c.is_a<semantics::class_instantiation> ())
+  {
+    return c.get<location_t> ("location");
+  }
+  else
+  {
+    return real_source_location (TYPE_NAME (c.tree_node ()));
+  }
+}
+
 string context::
 upcase (string const& s)
 {
diff --git a/odb/context.hxx b/odb/context.hxx
index a3a58bf..57e50a7 100644
--- a/odb/context.hxx
+++ b/odb/context.hxx
@@ -1150,6 +1150,14 @@ public:
   static semantics::path
   class_file (semantics::class_&);
 
+  // Return the location (as location_t; useful for comparison) of
+  // an "ODB class" (i.e., an object, view, or composite value),
+  // taking into account things like definition point overrides,
+  // etc.
+  //
+  location_t
+  class_location (semantics::class_&);
+
   // Database names and types.
   //
 public:
diff --git a/odb/include.cxx b/odb/include.cxx
index c397993..9c03f99 100644
--- a/odb/include.cxx
+++ b/odb/include.cxx
@@ -106,6 +106,8 @@ namespace
       path f;
       location_t l;
 
+      // Pretty much the same code as in context::class_location().
+      //
       if (c.count ("definition"))
       {
         l = c.get<location_t> ("definition");
diff --git a/odb/validator.cxx b/odb/validator.cxx
index 561d348..a843b59 100644
--- a/odb/validator.cxx
+++ b/odb/validator.cxx
@@ -1080,7 +1080,37 @@ namespace
         // Make sure the pointed-to class has object id unless it is in a
         // view where we can load no-id objects.
         //
-        if (id_member (*c) == 0 && !view_member (m))
+        if (semantics::data_member* id = id_member (*c))
+        {
+          semantics::type& idt (utype (*id));
+
+          // Make sure composite id is defined before this pointer. Failed
+          // that we get non-obvious C++ compiler errors in generated code.
+          //
+          using semantics::class_;
+
+          if (class_* comp = composite_wrapper (idt))
+          {
+            class_& s (dynamic_cast<class_&> (m.scope ()));
+
+            location_t idl (class_location (*comp));
+            location_t ml (class_location (s));
+
+            if (ml < idl)
+            {
+              error (m.location ())
+                << "composite object id " << class_fq_name (*comp) << " of "
+                << "pointed-to class " << class_fq_name (*c) << " must be "
+                << "defined before the pointer" << endl;
+
+              info (idl)
+                << "class " << class_name (*comp) << " is define here" << endl;
+
+              valid_ = false;
+            }
+          }
+        }
+        else if (!view_member (m))
         {
           os << m.file () << ":" << m.line () << ":" << m.column () << ": "
              << "error: pointed-to class '" << class_fq_name (*c) << "' "
-- 
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