#252 (['"[regression] no viable constructor for offset_ptr with clang from 1.87.0"])].

Author: igaztanaga

doc/interprocess.qbk

@@ -6866,6 +6866,7 @@ thank them:
 * Fixed bugs:
    * [@https://github.com/boostorg/interprocess/issues/242 GitHub #242 (['"Cygwin compatibility issues"])].
    * [@https://github.com/boostorg/interprocess/issues/247 GitHub #247 (['"destruction of move-constructed map using private_adaptive_pool triggers Assertion"])].
+   * [@https://github.com/boostorg/interprocess/issues/252 GitHub #252 (['"[regression] no viable constructor for offset_ptr with clang from 1.87.0"])].
 
 [endsect]
 

include/boost/interprocess/offset_ptr.hpp

@@ -251,6 +251,25 @@ namespace ipcdetail {
                    , Ret>
    {};
 
+   template <class T, class P>
+   struct is_ptr_constructible;
+
+   template <class T, class P>
+   struct is_ptr_constructible<T*, P*>
+   {
+      private:
+      template<class U> static U get();
+
+      template <typename U>
+      static yes_type test( typename enable_if_c< sizeof( new U*(get<P*>()) ) != 0, int >::type );
+         
+      template <typename U>
+      static no_type test(...);
+         
+      public:
+      static const bool value = sizeof(test<T>(0)) == sizeof(yes_type);
+   };
+
 }  //namespace ipcdetail {
 #endif   //#ifndef BOOST_INTERPROCESS_DOXYGEN_INVOKED
 
@@ -356,6 +375,20 @@ class offset_ptr
       : internal(ipcdetail::offset_ptr_to_offset<OffsetType>(static_cast<PointedType*>(ptr.get()), this))
    {}
 
+   //!Constructor from other offset_ptr. Only takes part in overload resolution
+   //!if PointedType* is constructible from T2* other than via a conversion (e.g. cast to a derived class). Never throws.
+   template<class T2>
+   BOOST_INTERPROCESS_FORCEINLINE explicit offset_ptr(const offset_ptr<T2, DifferenceType, OffsetType, OffsetAlignment> &ptr
+             #ifndef BOOST_INTERPROCESS_DOXYGEN_INVOKED
+             , typename ipcdetail::enable_if_c<
+                                                !::boost::move_detail::is_convertible<T2*, PointedType*>::value &&
+                                                ipcdetail::is_ptr_constructible<T2*, PointedType*>::value
+                                              >::type * = 0
+             #endif
+             ) BOOST_NOEXCEPT
+      : internal(ipcdetail::offset_ptr_to_offset<OffsetType>(static_cast<PointedType*>(ptr.get()), this))
+   {}
+
    #endif
 
    //!Emulates static_cast operator.

test/offset_ptr_test.cpp

@@ -411,24 +411,27 @@ void test_cast()
       pcvvoid_t pcvvoid = pvoid;
       pcvvoid = pvvoid;
 
-      //Test valid static_cast conversions
-      pint  = static_pointer_cast<int>(pvoid);
-      pcint = static_pointer_cast<const int>(pcvoid);
-      pvint = static_pointer_cast<volatile int>(pvoid);
-      pcvint = static_pointer_cast<const volatile int>(pvoid);
+      //Test valid static_cast conversions required by Allocator::pointer 
+      //requirements (void_pointer -> pointer, const_void_pointer -> const_pointer)
+      pint  = static_cast<pint_t>(pvoid);
+      pcint = static_cast<pcint_t>(pcvoid);
 
       BOOST_TEST(pint == pvoid);
       BOOST_TEST(pcint == pint);
-      BOOST_TEST(pvint == pint);
-      BOOST_TEST(pcvint == pint);
 
-      //Test valid static_cast conversions
+      //Test valid static_pointer_cast conversions
       {
          pint   = static_pointer_cast<int>(pvoid);
          pcint  = static_pointer_cast<const int>(pcvoid);
          pvint  = static_pointer_cast<volatile int>(pvoid);
          pcvint = static_pointer_cast<const volatile int>(pvoid);
 
+         BOOST_TEST(pint == pvoid);
+         BOOST_TEST(pcint == pcvoid);
+         BOOST_TEST(pcint == pint);
+         BOOST_TEST(pvint == pint);
+         BOOST_TEST(pcvint == pint);
+
          Derived d;
          offset_ptr<Derived> pd(&d);
          offset_ptr<Base> pb;
@@ -450,7 +453,7 @@ void test_cast()
          BOOST_TEST(pb3.get() == static_cast<Base3*>(pd3.get()));
       }
 
-      //Test valid const_cast conversions
+      //Test valid const_pointer_cast conversions
       {
          pint = const_pointer_cast<int>(pcint);
          pint = const_pointer_cast<int>(pvint);
@@ -462,14 +465,14 @@ void test_cast()
          pcint = const_pointer_cast<const int>(pvint);
          pcint = const_pointer_cast<const int>(pcvint);
 
-         //Test valid reinterpret_cast conversions
+         //Test valid reinterpret_pointer_cast conversions
          pint   = reinterpret_pointer_cast<int>(pvoid);
          pcint  = reinterpret_pointer_cast<const int>(pcvoid);
          pvint  = reinterpret_pointer_cast<volatile int>(pvoid);
          pcvint = reinterpret_pointer_cast<const volatile int>(pvoid);
       }
 
-      //Test valid dynamic_cast conversions
+      //Test valid dynamic_pointer_cast conversions
       {
          {
             Derived3 d3;