From 7d79d5298f56c4768a90df629b689d1bc3ebbb31 Mon Sep 17 00:00:00 2001
From: Karen Arutyunov <karen@codesynthesis.com>
Date: Thu, 17 Jan 2019 15:48:05 +0300
Subject: Add function_wrapper::cast() that cleanly cast to an incompatible
 function type

---
 odb/database.cxx                 |  2 +-
 odb/details/function-wrapper.hxx |  5 +++++
 odb/details/function-wrapper.ixx | 10 ++++++++++
 odb/schema-catalog.cxx           |  2 +-
 4 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/odb/database.cxx b/odb/database.cxx
index 7dd540f..f9e1043 100644
--- a/odb/database.cxx
+++ b/odb/database.cxx
@@ -67,7 +67,7 @@ namespace odb
     else
     {
       typedef void (*caller) (const void*, const char*, connection_type&);
-      reinterpret_cast<caller> (fw.function) (fw.std_function, name, c);
+      fw.cast<caller> () (fw.std_function, name, c);
     }
 
     return true;
diff --git a/odb/details/function-wrapper.hxx b/odb/details/function-wrapper.hxx
index 3a8ebfc..165df18 100644
--- a/odb/details/function-wrapper.hxx
+++ b/odb/details/function-wrapper.hxx
@@ -59,6 +59,11 @@ namespace odb
 
       void swap (function_wrapper<F>&);
 
+      // Cleanly cast to an incompatible function type.
+      //
+      template <typename R> R
+      cast () const;
+
       // Conversion to bool.
       //
     public:
diff --git a/odb/details/function-wrapper.ixx b/odb/details/function-wrapper.ixx
index d73d578..9ec19ec 100644
--- a/odb/details/function-wrapper.ixx
+++ b/odb/details/function-wrapper.ixx
@@ -36,5 +36,15 @@ namespace odb
       swap (const_cast<function_wrapper<F>&> (x));
       return *this;
     }
+
+    template <typename F>
+    template <typename R>
+    inline R function_wrapper<F>::
+    cast () const
+    {
+      union { F* f; R r; } r;
+      r.f = function;
+      return r.r;
+    }
   }
 }
diff --git a/odb/schema-catalog.cxx b/odb/schema-catalog.cxx
index b767bca..946884f 100644
--- a/odb/schema-catalog.cxx
+++ b/odb/schema-catalog.cxx
@@ -227,7 +227,7 @@ namespace odb
         else
         {
           typedef void (*caller) (const void*, database&);
-          reinterpret_cast<caller> (m.function) (m.std_function, db);
+          m.cast<caller> () (m.std_function, db);
         }
         r++;
       }
-- 
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