From d9af320fbdfdadd70815d4f14a9116829dfabdf0 Mon Sep 17 00:00:00 2001
From: Karen Arutyunov <karen@codesynthesis.com>
Date: Fri, 2 Nov 2018 17:16:31 +0300
Subject: Generalize function_cast() to cast between incompatible function
 pointers

---
 libbutl/utility.ixx | 6 +++---
 libbutl/utility.mxx | 7 ++++---
 2 files changed, 7 insertions(+), 6 deletions(-)

(limited to 'libbutl')

diff --git a/libbutl/utility.ixx b/libbutl/utility.ixx
index e17462a..1aa116b 100644
--- a/libbutl/utility.ixx
+++ b/libbutl/utility.ixx
@@ -213,11 +213,11 @@ namespace butl
     return nullopt;
   }
 
-  template <typename F>
+  template <typename F, typename P>
   inline F
-  function_cast (void* p)
+  function_cast (P* p)
   {
-    union { void* p; F f; } r;
+    union { P* p; F f; } r;
     r.p = p;
     return r.f;
   }
diff --git a/libbutl/utility.mxx b/libbutl/utility.mxx
index f944599..5d093ad 100644
--- a/libbutl/utility.mxx
+++ b/libbutl/utility.mxx
@@ -315,11 +315,12 @@ LIBBUTL_MODEXPORT namespace butl
     F f_;
   };
 
-  // Cleanly cast dlsym() result (void*) to a function pointer.
+  // Cleanly cast between incompatible function types or dlsym() result
+  // (void*) to a function pointer.
   //
-  template <typename F>
+  template <typename F, typename P>
   F
-  function_cast (void*);
+  function_cast (P*);
 
   // Call a function if there is an exception.
   //
-- 
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