Re: [committed] libstdc++: Fix noexcept on dtors in <experimental/scope> [PR114152]

[Jonathan Wakely <jwakely@redhat.com>]

Oops, sorry, I CC'd the wrong Victor on this patch (you've both
reported libstdc++ bugs today and I grabbed the email address from the
wrong browser tab).

On Wed, 28 Feb 2024 at 14:53, Jonathan Wakely wrote:
>
> Tested x86_64-linux, pushed to trunk. Backport to gcc-13 to follow.
>
> -- >8 --
>
> The PR points out that the destructors all have incorrect
> noexcept-specifiers.
>
> libstdc++-v3/ChangeLog:
>
>         PR libstdc++/114152
>         * include/experimental/scope (scope_exit scope_fail): Make
>         destructor unconditionally noexcept.
>         (scope_sucess): Fix noexcept-specifier.
>         * testsuite/experimental/scopeguard/114152.cc: New test.
> ---
>  libstdc++-v3/include/experimental/scope       |  6 ++---
>  .../experimental/scopeguard/114152.cc         | 24 +++++++++++++++++++
>  2 files changed, 27 insertions(+), 3 deletions(-)
>  create mode 100644 libstdc++-v3/testsuite/experimental/scopeguard/114152.cc
>
> diff --git a/libstdc++-v3/include/experimental/scope b/libstdc++-v3/include/experimental/scope
> index 5dbeac14795..ea273e8c095 100644
> --- a/libstdc++-v3/include/experimental/scope
> +++ b/libstdc++-v3/include/experimental/scope
> @@ -97,7 +97,7 @@ namespace experimental::inline fundamentals_v3
>        scope_exit& operator=(const scope_exit&) = delete;
>        scope_exit& operator=(scope_exit&&) = delete;
>
> -      ~scope_exit() noexcept(noexcept(this->_M_exit_function))
> +      ~scope_exit() noexcept
>        {
>         if (_M_execute_on_destruction)
>           _M_exit_function();
> @@ -157,7 +157,7 @@ namespace experimental::inline fundamentals_v3
>        scope_fail& operator=(const scope_fail&) = delete;
>        scope_fail& operator=(scope_fail&&) = delete;
>
> -      ~scope_fail() noexcept(noexcept(this->_M_exit_function))
> +      ~scope_fail() noexcept
>        {
>         if (std::uncaught_exceptions() > _M_uncaught_init)
>           _M_exit_function();
> @@ -211,7 +211,7 @@ namespace experimental::inline fundamentals_v3
>        scope_success& operator=(const scope_success&) = delete;
>        scope_success& operator=(scope_success&&) = delete;
>
> -      ~scope_success() noexcept(noexcept(this->_M_exit_function))
> +      ~scope_success() noexcept(noexcept(this->_M_exit_function()))
>        {
>         if (std::uncaught_exceptions() <= _M_uncaught_init)
>           _M_exit_function();
> diff --git a/libstdc++-v3/testsuite/experimental/scopeguard/114152.cc b/libstdc++-v3/testsuite/experimental/scopeguard/114152.cc
> new file mode 100644
> index 00000000000..63c1f710e9f
> --- /dev/null
> +++ b/libstdc++-v3/testsuite/experimental/scopeguard/114152.cc
> @@ -0,0 +1,24 @@
> +// { dg-do compile { target c++20 } }
> +
> +// PR libstdc++/114152
> +// Wrong exception specifiers for LFTSv3 scope guard destructors
> +
> +#include <experimental/scope>
> +
> +using namespace std::experimental;
> +
> +struct F {
> +  void operator()() noexcept(false);
> +};
> +
> +static_assert( noexcept(std::declval<scope_exit<F>&>().~scope_exit()) );
> +static_assert( noexcept(std::declval<scope_fail<F>&>().~scope_fail()) );
> +static_assert( ! noexcept(std::declval<scope_success<F>&>().~scope_success()) );
> +
> +struct G {
> +  void operator()() noexcept(true);
> +};
> +
> +static_assert( noexcept(std::declval<scope_exit<G>&>().~scope_exit()) );
> +static_assert( noexcept(std::declval<scope_fail<G>&>().~scope_fail()) );
> +static_assert( noexcept(std::declval<scope_success<G>&>().~scope_success()) );
> --
> 2.43.0
>