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Fix just_from submit exception specification #2212

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Merged
ericniebler merged 2 commits into from
Aug 18, 2026
Merged

Fix just_from submit exception specification #2212

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9ec59c6
Make just_from submit conditionally noexcept
fallintoplace Aug 16, 2026
5742a1f
Address just_from submit review
fallintoplace Aug 16, 2026
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5 changes: 3 additions & 2 deletions include/exec/just_from.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -172,15 +172,16 @@ namespace experimental::execution

template <class Rcvr>
STDEXEC_ATTRIBUTE(host, device)
auto submit(Rcvr rcvr) && noexcept -> void
auto submit(Rcvr rcvr) && noexcept(STDEXEC::__nothrow_decay_copyable<Rcvr, Fn>) -> void

@ericniebler ericniebler Aug 16, 2026

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receivers are now required to be nothrow move constructible, so this check is unnecessary.

Suggested change
auto submit(Rcvr rcvr) && noexcept(STDEXEC::__nothrow_decay_copyable<Rcvr, Fn>) -> void
auto submit(Rcvr rcvr) && noexcept(STDEXEC::__nothrow_decay_copyable<Fn>) -> void

{
auto op = static_cast<_sndr_base&&>(*this).connect(static_cast<Rcvr&&>(rcvr));
STDEXEC::start(op);
}

template <class Rcvr>
STDEXEC_ATTRIBUTE(host, device)
auto submit(Rcvr rcvr) const & noexcept -> void
auto submit(Rcvr rcvr) const & noexcept(STDEXEC::__nothrow_decay_copyable<Rcvr, Fn const &>)

@ericniebler ericniebler Aug 16, 2026

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Suggested change
auto submit(Rcvr rcvr) const & noexcept(STDEXEC::__nothrow_decay_copyable<Rcvr, Fn const &>)
auto submit(Rcvr rcvr) const & noexcept(STDEXEC::__nothrow_decay_copyable<Fn const &>)

-> void
{
auto op = this->connect(static_cast<Rcvr&&>(rcvr));
STDEXEC::start(op);
Expand Down
36 changes: 29 additions & 7 deletions test/exec/test_just_from.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
*/

#include "exec/just_from.hpp"
#include "test_common/receivers.hpp"
#include "test_common/tuple.hpp"
#include "test_common/type_helpers.hpp"

Expand All @@ -26,13 +27,19 @@ namespace

struct throwing_move_callable
{
throwing_move_callable() = default;
throwing_move_callable(throwing_move_callable const &) noexcept = default;
throwing_move_callable(throwing_move_callable &&other) noexcept(false)
explicit throwing_move_callable(bool& should_throw) noexcept
: should_throw_(&should_throw)
{}

throwing_move_callable(throwing_move_callable const &other) noexcept
: should_throw_(other.should_throw_)
{}

throwing_move_callable(throwing_move_callable&& other) noexcept(false)
: should_throw_(other.should_throw_)
{
#if !STDEXEC_NO_STDCPP_EXCEPTIONS()
if (should_throw_)
if (*should_throw_)
{
throw 42;
}
Expand All @@ -45,7 +52,7 @@ namespace
return sink();
}

bool should_throw_{false};
bool* should_throw_;
};

TEST_CASE("just_from is a sender", "[just_from]")
Expand Down Expand Up @@ -94,15 +101,30 @@ namespace
};
STATIC_REQUIRE(noexcept(exec::just_from(nothrow_fn)));

throwing_move_callable fn;
bool should_throw = false;
throwing_move_callable fn{should_throw};
STATIC_REQUIRE_FALSE(noexcept(exec::just_from(fn)));

#if !STDEXEC_NO_STDCPP_EXCEPTIONS()
fn.should_throw_ = true;
should_throw = true;
CHECK_THROWS_AS(exec::just_from(fn), int);
#endif
}

TEST_CASE("just_from submit is conditionally noexcept", "[just_from]")
{
bool should_throw = false;
auto s = exec::just_from(throwing_move_callable{should_throw});

STATIC_REQUIRE_FALSE(noexcept(static_cast<decltype(s)&&>(s).submit(empty_recv::recv0{})));
STATIC_REQUIRE(noexcept(s.submit(empty_recv::recv0{})));

#if !STDEXEC_NO_STDCPP_EXCEPTIONS()
should_throw = true;
CHECK_THROWS_AS(static_cast<decltype(s)&&>(s).submit(empty_recv::recv0{}), int);
#endif
}

TEST_CASE("just_from with multiple completions", "[just_from]")
{
auto fn = [](auto sink) noexcept
Expand Down
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