Re: [PATCH v2 01/10] Add handle_eintr to wrap EINTR handling in syscalls

Simon Marchi
2020-09-07T14:06:17Z

On 2020-09-03 8:28 p.m., Kamil Rytarowski wrote:
> gdbsupport/ChangeLog:
>
> * eintr.h: New file.
> ---
> gdbsupport/ChangeLog | 4 ++++
> gdbsupport/eintr.h | 41 +++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 45 insertions(+)
> create mode 100644 gdbsupport/eintr.h
>
> diff --git a/gdbsupport/ChangeLog b/gdbsupport/ChangeLog
> index a1960537384..d26000e36ac 100644
> --- a/gdbsupport/ChangeLog
> +++ b/gdbsupport/ChangeLog
> @@ -1,3 +1,7 @@
> +2020-09-04 Kamil Rytarowski <n54@gmx.com>
> +
> + * eintr.h: New file.
> +
> 2020-08-13 Simon Marchi <simon.marchi@polymtl.ca>
>
> * selftest.h (run_tests): Change parameter to array_view.
> diff --git a/gdbsupport/eintr.h b/gdbsupport/eintr.h
> new file mode 100644
> index 00000000000..74b7038da60
> --- /dev/null
> +++ b/gdbsupport/eintr.h
> @@ -0,0 +1,41 @@
> +/* Utility for handling interrupted syscalls by signals.
> +
> + Copyright (C) 2020 Free Software Foundation, Inc.
> +
> + This file is part of GDB.
> +
> + This program is free software; you can redistribute it and/or modify
> + it under the terms of the GNU General Public License as published by
> + the Free Software Foundation; either version 3 of the License, or
> + (at your option) any later version.
> +
> + This program is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + GNU General Public License for more details.
> +
> + You should have received a copy of the GNU General Public License
> + along with this program. If not, see <http://www.gnu.org/licenses/>. */
> +
> +#ifndef GDBSUPPORT_EINTR_H
> +#define GDBSUPPORT_EINTR_H
> +
> +#include <cerrno>
> +
> +namespace gdb
> +{
> +template <typename Ret, typename Fun, typename... Args>
> +inline Ret handle_eintr (const Ret &R, const Fun &F, const Args &... A)
> +{
> + Ret ret;
> + do
> + {
> + errno = 0;
> + ret = F (A...);
> + }
> + while (ret == R && errno == EINTR);
> + return ret;
> +}
> +}

Can you document this function a little bit, including a usage example? I tried
to apply it in gdb/linux-nat.c, function async_file_mark, but I'm not sure I'm
doing it correctly. In particular, what should I pass as the `R` parameter? Does
that make sense?

gdb::handle_eintr (-1, ::write, linux_nat_event_pipe[1], "+", 1);

Simon