Make any_cast compare typeinfo as well as function pointers

It's possible for the function pointer comparison to fail even though
the type is correct, because the function could be defined multiple
times with different addresses when shared libraries are in use.

Retain the function pointer check for the common case where the check
succeeds, but compare typeinfo (if RTTI is enabled) if the first check
fails.

	* include/experimental/any (__any_caster): Use RTTI if comparing
	addresses fails, to support non-unique addresses in shared libraries.
	* include/std/any (__any_caster): Likewise.

From-SVN: r271557

libstdc++-v3/ChangeLog

 2019-05-23  Jonathan Wakely  <jwakely@redhat.com>
 
+	* include/experimental/any (__any_caster): Use RTTI if comparing
+	addresses fails, to support non-unique addresses in shared libraries.
+	* include/std/any (__any_caster): Likewise.
+
 	PR libstdc++/90220
 	* include/experimental/any (__any_caster): Constrain to only be
 	callable for object types. Use remove_cv_t instead of decay_t.

libstdc++-v3/include/experimental/any

@@ -432,11 +432,18 @@ inline namespace fundamentals_v1
       // is explicitly specialized and has a no-op _S_manage function.
       using _Vp = conditional_t<__and_<__does_not_decay, __is_copyable>::value,
 				_Up, any::_Op>;
-      if (__any->_M_manager != &any::_Manager<_Vp>::_S_manage)
-	return nullptr;
-      any::_Arg __arg;
-      __any->_M_manager(any::_Op_access, __any, &__arg);
-      return __arg._M_obj;
+      // First try comparing function addresses, which works without RTTI
+      if (__any->_M_manager == &any::_Manager<_Vp>::_S_manage
+#if __cpp_rtti
+	  || __any->type() == typeid(_Tp)
+#endif
+	  )
+	{
+	  any::_Arg __arg;
+	  __any->_M_manager(any::_Op_access, __any, &__arg);
+	  return __arg._M_obj;
+	}
+      return nullptr;
     }
 
   // This overload exists so that std::any_cast<void(*)()>(a) is well-formed.

libstdc++-v3/include/std/any

@@ -503,6 +503,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     }
   // @}
 
+  /// @cond undocumented
   template<typename _Tp>
     void* __any_caster(const any* __any)
     {
@@ -516,8 +517,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       // Only copy constructible types can be used for contained values:
       else if constexpr (!is_copy_constructible_v<_Up>)
 	return nullptr;
-      // This check is equivalent to __any->type() == typeid(_Tp)
-      else if (__any->_M_manager == &any::_Manager<_Up>::_S_manage)
+      // First try comparing function addresses, which works without RTTI
+      else if (__any->_M_manager == &any::_Manager<_Up>::_S_manage
+#if __cpp_rtti
+	  || __any->type() == typeid(_Tp)
+#endif
+	  )
 	{
 	  any::_Arg __arg;
 	  __any->_M_manager(any::_Op_access, __any, &__arg);
@@ -525,6 +530,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	}
       return nullptr;
     }
+  /// @endcond
 
   /**
    * @brief Access the contained object.