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[2026-03 LWG Motion 22] P3450R1 Extend std::is_within_lifetime #8881

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[2026-03 LWG Motion 22] P3450R1 Extend std::is_within_lifetime #8881

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14 changes: 11 additions & 3 deletions source/meta.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -647,7 +647,8 @@

// \ref{meta.const.eval}, constant evaluation context
constexpr bool is_constant_evaluated() noexcept;
consteval bool is_within_lifetime(const auto*) noexcept;
template<class U=void, class T>
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@frederick-vs-ja frederick-vs-ja Mar 30, 2026

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Suggested change
template<class U=void, class T>
template<class U = void, class T>

I think we generally insert spaces around = for default template arguments. Although I haven't found such a formal rule in https://github.com/cplusplus/draft/wiki/Specification-Style-Guidelines.

consteval bool is_within_lifetime(const T*) noexcept;
}
\end{codeblock}

Expand Down Expand Up @@ -2844,14 +2845,21 @@

\indexlibraryglobal{is_within_lifetime}%
\begin{itemdecl}
consteval bool is_within_lifetime(const auto* p) noexcept;
template<class U=void, class T>
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@frederick-vs-ja frederick-vs-ja Mar 30, 2026

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Suggested change
template<class U=void, class T>
template<class U = void, class T>

consteval bool is_within_lifetime(const T* p) noexcept;
\end{itemdecl}

\begin{itemdescr}
\pnum
\mandates
\tcode{static_cast<const volatile U*>(p)} is well-formed.

\pnum
\returns
\tcode{true} if \tcode{p} is a pointer to an object that is
within its lifetime\iref{basic.life}; otherwise, \tcode{false}.
within its lifetime\iref{basic.life} and
\tcode{static_cast<const volatile U*>(p)} is a constant subexpression;
otherwise, \tcode{false}.

\pnum
\remarks
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2 changes: 1 addition & 1 deletion source/support.tex
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Expand Up @@ -749,7 +749,7 @@
#define @\defnlibxname{cpp_lib_is_sufficiently_aligned}@ 202411L // freestanding, also in \libheader{memory}
#define @\defnlibxname{cpp_lib_is_swappable}@ 201603L // freestanding, also in \libheader{type_traits}
#define @\defnlibxname{cpp_lib_is_virtual_base_of}@ 202406L // freestanding, also in \libheader{type_traits}
#define @\defnlibxname{cpp_lib_is_within_lifetime}@ 202306L // freestanding, also in \libheader{type_traits}
#define @\defnlibxname{cpp_lib_is_within_lifetime}@ 202603L // freestanding, also in \libheader{type_traits}
#define @\defnlibxname{cpp_lib_jthread}@ 201911L // also in \libheader{stop_token}, \libheader{thread}
#define @\defnlibxname{cpp_lib_latch}@ 201907L // also in \libheader{latch}
#define @\defnlibxname{cpp_lib_launder}@ 201606L // freestanding, also in \libheader{new}
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