https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80473
Bug ID: 80473
Summary: [7/8 Regression] notes about over-aligned new not
suppressed in system-headers
Product: gcc
Version: 7.0.1
Status: UNCONFIRMED
Keywords: diagnostic
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Target Milestone: ---
#include <type_traits>
struct alignas(64) A { int i; };
constexpr bool b = std::is_constructible<A, A>::value;
With -Wall this produces unhelpful output referring to an unevaluated
new-expression inside libstdc++ internals:
In file included from a2.cc:1:0:
/home/jwakely/gcc/7/include/c++/7.0.1/type_traits: In substitution of
‘template<class _Tp, class _Arg> struct
std::__is_direct_constructible_impl<_Tp, _Arg, decltype (::new _Tp)> [with _Tp
= A; _Arg = A]’:
/home/jwakely/gcc/7/include/c++/7.0.1/type_traits:143:12: required from
‘struct std::__and_<std::is_destructible<A>,
std::__is_direct_constructible_impl<A, A, void> >’
/home/jwakely/gcc/7/include/c++/7.0.1/type_traits:995:12: required from
‘struct std::__is_direct_constructible_new_safe<A, A>’
/home/jwakely/gcc/7/include/c++/7.0.1/type_traits:1077:12: required from
‘struct std::__is_direct_constructible_new<A, A>’
/home/jwakely/gcc/7/include/c++/7.0.1/type_traits:1085:12: required from
‘struct std::__is_direct_constructible<A, A>’
/home/jwakely/gcc/7/include/c++/7.0.1/type_traits:1125:12: required from
‘struct std::__is_constructible_impl<A, A>’
/home/jwakely/gcc/7/include/c++/7.0.1/type_traits:1136:12: required from
‘struct std::is_constructible<A, A>’
a2.cc:3:47: required from here
/home/jwakely/gcc/7/include/c++/7.0.1/type_traits:990:16: note: uses ‘void*
operator new(long unsigned int)’, which does not have an alignment parameter
decltype(::new _Tp(std::declval<_Arg>()))>
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/jwakely/gcc/7/include/c++/7.0.1/type_traits:990:16: note: use
‘-faligned-new’ to enable C++17 over-aligned new support
The actual -Waligned-new warning is suppressed due to being in a system header,
but the note is not.
It's debatable whether warning about the new-expression as an unevaluated
operand is useful anyway, but the note should not be printed if the warning is
suppressed.
