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P2927R3 Inspecting exception_ptr #7976

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Jul 15, 2025
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P2927R3 Inspecting exception_ptr #7976

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32 changes: 31 additions & 1 deletion source/support.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -665,6 +665,7 @@
#define @\defnlibxname{cpp_lib_erase_if}@ 202002L
// also in \libheader{string}, \libheader{deque}, \libheader{forward_list}, \libheader{list}, \libheader{vector}, \libheader{map}, \libheader{set}, \libheader{unordered_map},
// \libheader{unordered_set}
#define @\defnlibxname{cpp_lib_exception_ptr_cast}@ 202506L // also in \libheader{exception}
#define @\defnlibxname{cpp_lib_exchange_function}@ 201304L // freestanding, also in \libheader{utility}
#define @\defnlibxname{cpp_lib_execution}@ 201902L // also in \libheader{execution}
#define @\defnlibxname{cpp_lib_expected}@ 202211L // also in \libheader{expected}
Expand Down Expand Up @@ -3864,6 +3865,8 @@
constexpr exception_ptr current_exception() noexcept;
[[noreturn]] constexpr void rethrow_exception(exception_ptr p);
template<class E> constexpr exception_ptr make_exception_ptr(E e) noexcept;
template<class E> const E* exception_ptr_cast(const exception_ptr& p) noexcept;
template<class E> void exception_ptr_cast(const exception_ptr&&) = delete;

template<class T> [[noreturn]] constexpr void throw_with_nested(T&& t);
template<class E> constexpr void rethrow_if_nested(const E& e);
Expand Down Expand Up @@ -4143,7 +4146,8 @@
For purposes of determining the presence of a data race, operations on
\tcode{exception_ptr} objects shall access and modify only the
\tcode{exception_ptr} objects themselves and not the exceptions they refer to.
Use of \tcode{rethrow_exception} on \tcode{exception_ptr} objects that refer to
Use of \tcode{rethrow_exception} or \tcode{exception_ptr_cast}
on \tcode{exception_ptr} objects that refer to
the same exception object shall not introduce a data race.
\begin{note}
If
Expand Down Expand Up @@ -4240,6 +4244,32 @@
\end{note}
\end{itemdescr}

\indexlibraryglobal{exception_ptr_cast}%
\begin{itemdecl}
template<class E> const E* exception_ptr_cast(const exception_ptr& p) noexcept;
\end{itemdecl}

\begin{itemdescr}
\pnum
\mandates
\tcode{E} is a cv-unqualified complete object type.
\tcode{E} is not an array type.
\tcode{E} is not a pointer or pointer-to-member type.
\begin{note}
When \tcode{E} is a pointer or pointer-to-member type,
a handler of type \tcode{const E\&} can match
without binding to the exception object itself.
\end{note}

\pnum
\returns
A pointer to the exception object referred to by \tcode{p},
if \tcode{p} is not null and
a handler of type \tcode{const E\&}
would be a match\iref{except.handle} for that exception object.
Otherwise, \tcode{nullptr}.
\end{itemdescr}

\rSec2[except.nested]{\tcode{nested_exception}}

\indexlibraryglobal{nested_exception}%
Expand Down