lib/sys-limits.h

   1 /* System call limits
   2
   3    Copyright 2018-2019 Free Software Foundation, Inc.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2, or (at your option)
   8    any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #ifndef _GL_SYS_LIMITS_H
  19 #define _GL_SYS_LIMITS_H
  20
  21 #include <limits.h>
  22
  23 /* Maximum number of bytes to read or write in a single system call.
  24    This can be useful for system calls like sendfile on GNU/Linux,
  25    which do not handle more than MAX_RW_COUNT bytes correctly.
  26    The Linux kernel MAX_RW_COUNT is at least INT_MAX >> 20 << 20,
  27    where the 20 comes from the Hexagon port with 1 MiB pages; use that
  28    as an approximation, as the exact value may not be available to us.
  29
  30    Using this also works around a serious Linux bug before 2.6.16; see
  31    <https://bugzilla.redhat.com/show_bug.cgi?id=612839>.
  32
  33    Using this also works around a Tru64 5.1 bug, where attempting
  34    to read INT_MAX bytes fails with errno == EINVAL.  See
  35    <https://lists.gnu.org/r/bug-gnu-utils/2002-04/msg00010.html>.
  36
  37    Using this is likely to work around similar bugs in other operating
  38    systems.  */
  39
  40 enum { SYS_BUFSIZE_MAX = INT_MAX >> 20 << 20 };
  41
  42 #endif