[PATCH] libstdc++: unused local declarations

[Jonathan Wakely]

On Wed, 28 Aug 2024 at 10:38, Jason Merrill <jason@redhat.com> wrote:
>
> Tested x86_64-pc-linux-gnu.  OK for trunk, or were these supposed to be used?

I think the _RefT typedef was used in an earlier version of the code
(possibly a much earlier version that was never even pushed). It can
be removed.

I think the __ok variable exists to force constant evaluation of
__check_dynamic_spec_types, although I think that could be done this
way instead:

if (is_constant_evaluated())
  __check_dynamic_spec_types();

I'll take care of both changes today, so please don't bother pushing this.


>
> -- 8< --
>
> The __ok variable and _RefT typedef aren't used in the rest of their blocks.
> Should they be?
>
> libstdc++-v3/ChangeLog:
>
>         * include/std/format (check_dynamic_spec): Add [[maybe_unused]].
>         * include/std/ranges (to): Likewise.
> ---
>  libstdc++-v3/include/std/format | 1 +
>  libstdc++-v3/include/std/ranges | 2 +-
>  2 files changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format
> index 3280dadfb90..376169018ba 100644
> --- a/libstdc++-v3/include/std/format
> +++ b/libstdc++-v3/include/std/format
> @@ -4323,6 +4323,7 @@ namespace __format
>      constexpr void
>      basic_format_parse_context<_CharT>::check_dynamic_spec(size_t __id) noexcept
>      {
> +      [[maybe_unused]]
>        constexpr bool __ok = __check_dynamic_spec_types<_Ts...>();
>
>        if consteval {
> diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
> index b7c7aa36ddc..008461e556b 100644
> --- a/libstdc++-v3/include/std/ranges
> +++ b/libstdc++-v3/include/std/ranges
> @@ -9327,7 +9327,7 @@ namespace __detail
>                          std::forward<_Args>(__args)...);
>           else
>             {
> -             using _RefT = range_reference_t<_Rg>;
> +             using _RefT [[maybe_unused]] = range_reference_t<_Rg>;
>               static_assert(constructible_from<_Cont, _Args...>);
>               _Cont __c(std::forward<_Args>(__args)...);
>               if constexpr (sized_range<_Rg>
>
> base-commit: 48032f28ad4bc5e810c303229bcaa223a0c4d09f
> --
> 2.46.0
>