gdbsupport/scoped_ignore_sigttou.h

/* Support for ignoring SIGTTOU.

   Copyright (C) 2003-2023 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 SCOPED_IGNORE_SIGTTOU_H
#define SCOPED_IGNORE_SIGTTOU_H

#include "gdbsupport/scoped_ignore_signal.h"
#include "gdbsupport/job-control.h"

#ifdef SIGTTOU

/* Simple wrapper that allows lazy initialization / destruction of T.
   Slightly more efficient than std::optional, because it doesn't
   carry storage to track whether the object has been initialized.  */
template<typename T>
class lazy_init
{
public:
  void emplace ()
  {
    new (&m_u.obj) T ();
  }

  void reset ()
  {
    m_u.obj.~T ();
  }

private:
  union u
  {
    /* Must define ctor/dtor if T has non-trivial ctor/dtor.  */
    u () {}
    ~u () {}

    T obj;
  } m_u;
};

/* RAII class used to ignore SIGTTOU in a scope.  This isn't simply
   scoped_ignore_signal<SIGTTOU> because we want to check the
   `job_control' global.  */

class scoped_ignore_sigttou
{
public:
  scoped_ignore_sigttou ()
  {
    if (job_control)
      m_ignore_signal.emplace ();
  }

  ~scoped_ignore_sigttou ()
  {
    if (job_control)
      m_ignore_signal.reset ();
  }

  DISABLE_COPY_AND_ASSIGN (scoped_ignore_sigttou);

private:
  lazy_init<scoped_ignore_signal<SIGTTOU, false>> m_ignore_signal;
};

#else

using scoped_ignore_sigttou = scoped_ignore_signal_nop;

#endif

#endif /* SCOPED_IGNORE_SIGTTOU_H */