Fix debug mode assertion for std::shared_ptr<void>

	* include/bits/shared_ptr_base.h
	(__shared_ptr_access<T, L, false, true>::operator->()): Fix assertion.

From-SVN: r243303

libstdc++-v3/ChangeLog

+2016-12-06  Jonathan Wakely  <jwakely@redhat.com>
+
+	* include/bits/shared_ptr_base.h
+	(__shared_ptr_access<T, L, false, true>::operator->()): Fix assertion.
+
 2016-12-06  Ville Voutilainen  <ville.voutilainen@gmail.com>
 
 	Constrain optional's __constexpr_addressof in its return type

libstdc++-v3/include/bits/shared_ptr_base.h

@@ -983,8 +983,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       element_type*
       operator->() const noexcept
       {
-	_GLIBCXX_DEBUG_PEDASSERT(_M_get() != nullptr);
-	return static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get();
+	auto __ptr = static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get();
+	_GLIBCXX_DEBUG_PEDASSERT(__ptr != nullptr);
+	return __ptr;
       }
     };