gdbsupport/eintr.h

   1 /* Utility for handling interrupted syscalls by signals.
   2
   3    Copyright (C) 2020 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef GDBSUPPORT_EINTR_H
  21 #define GDBSUPPORT_EINTR_H
  22
  23 #include <cerrno>
  24
  25 namespace gdb
  26 {
  27 /* Repeat a system call interrupted with a signal.
  28
  29    A utility for handling interrupted syscalls, which return with error
  30    and set the errno to EINTR.  The interrupted syscalls can be repeated,
  31    until successful completion.  This utility avoids wrapping code with
  32    manual checks for such errors which are highly repetitive.
  33
  34    For example, with:
  35
  36    ssize_t ret;
  37    do
  38      {
  39        errno = 0;
  40        ret = ::write (pipe[1], "+", 1);
  41      }
  42    while (ret == -1 && errno == EINTR);
  43
  44    You could wrap it by writing the wrapped form:
  45
  46    ssize_t ret = gdb::handle_eintr<ssize_t> (-1, ::write, pipe[1], "+", 1);
  47
  48    The RET typename specifies the return type of the wrapped system call, which
  49    is typically int or ssize_t.  The R argument specifies the failure value
  50    indicating the interrupted syscall when calling the F function with
  51    the A... arguments.  */
  52
  53 template <typename Ret, typename Fun, typename... Args>
  54 inline Ret handle_eintr (const Ret &R, const Fun &F, const Args &... A)
  55 {
  56   Ret ret;
  57   do
  58     {
  59       errno = 0;
  60       ret = F (A...);
  61     }
  62   while (ret == R && errno == EINTR);
  63   return ret;
  64 }
  65 }
  66
  67 #endif /* GDBSUPPORT_EINTR_H */