On Tue, Jun 10, 2025 at 5:22 AM Patrick Palka <[email protected]> wrote:
> Tested on x86_64-pc-linux-gnu, does this look OK for trunk?
>
LGTM. I think this change makes sense, and we should consider requiring
that in standard.
For example, with reflections, this allows reflect_constant to store
distance for all range types.
>
> -- >8 --
>
> This patch makes these integer-class types structural types by
> public-izing their data memberss so that they could be used as NTTP
> types. I don't think the standard requires this, but it seems
> like a useful extension.
> libstdc++-v3/ChangeLog:
>
> * include/bits/max_size_type.h (__max_size_type::_M_val): Make
> public instead of private.
> (__max_size_type::_M_msb): Likewise.
> (__max_diff_type::_M_rep): Likewise.
> * testsuite/std/ranges/iota/max_size_type.cc: Verify
> __max_diff_type and __max_size_type are structural.
> ---
> libstdc++-v3/include/bits/max_size_type.h | 4 ++--
> libstdc++-v3/testsuite/std/ranges/iota/max_size_type.cc | 7 +++++++
> 2 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/max_size_type.h
> b/libstdc++-v3/include/bits/max_size_type.h
> index 5bec0b5a519a..e602b1b4bee5 100644
> --- a/libstdc++-v3/include/bits/max_size_type.h
> +++ b/libstdc++-v3/include/bits/max_size_type.h
> @@ -425,10 +425,11 @@ namespace ranges
> using __rep = unsigned long long;
> #endif
> static constexpr size_t _S_rep_bits = sizeof(__rep) * __CHAR_BIT__;
> - private:
> +
> __rep _M_val = 0;
> unsigned _M_msb:1 = 0;
>
> + private:
> constexpr explicit
> __max_size_type(__rep __val, int __msb) noexcept
> : _M_val(__val), _M_msb(__msb)
> @@ -752,7 +753,6 @@ namespace ranges
> { return !(__l < __r); }
> #endif
>
> - private:
> __max_size_type _M_rep = 0;
>
> friend class __max_size_type;
> diff --git a/libstdc++-v3/testsuite/std/ranges/iota/max_size_type.cc
> b/libstdc++-v3/testsuite/std/ranges/iota/max_size_type.cc
> index 3e6f954ceb0c..4739d9e2f790 100644
> --- a/libstdc++-v3/testsuite/std/ranges/iota/max_size_type.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/iota/max_size_type.cc
> @@ -400,6 +400,13 @@ static_assert(max_diff_t(max_size_t(1)
> << (numeric_limits<max_size_t>::digits-1))
> == numeric_limits<max_diff_t>::min());
>
> +// Verify that the types are structural types and can therefore be used
> +// as NTTP types.
> +template<max_size_t V> struct Su { static_assert(V*V == V+132); };
> +template<max_diff_t V> struct Ss { static_assert(V*V == V+132); };
> +template struct Su<12>;
> +template struct Ss<12>;
> +
> int
> main()
> {
> --
> 2.50.0.rc1.89.g8db3019401
>
>
