text: /*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
  │vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
  ╞══════════════════════════════════════════════════════════════════════════════╡
  │ Copyright 2020 Justine Alexandra Roberts Tunney                              │
  │                                                                              │
  │ Permission to use, copy, modify, and/or distribute this software for         │
  │ any purpose with or without fee is hereby granted, provided that the         │
  │ above copyright notice and this permission notice appear in all copies.      │
  │                                                                              │
  │ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
  │ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
  │ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
  │ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
  │ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
  │ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
  │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
  │ PERFORMANCE OF THIS SOFTWARE.                                                │
  ╚─────────────────────────────────────────────────────────────────────────────*/
  #include "libc/assert.h"
  #include "libc/calls/calls.h"
  #include "libc/calls/internal.h"
  #include "libc/dce.h"
  #include "libc/macros.h"
  #include "libc/sysv/consts/msync.h"
  
  /**
   * Synchronize memory mapping changes to disk.
   *
   * Without this, there's no guarantee memory is written back to disk. In
   * practice, what that means is just Windows NT.
   *
   * @param flags needs MS_ASYNC or MS_SYNC and can have MS_INVALIDATE
   * @return 0 on success or -1 w/ errno
   */
  int msync(void *addr, size_t size, int flags) {
    assert(((flags & MS_SYNC) ^ (flags & MS_ASYNC)) || !(MS_SYNC && MS_ASYNC));
    if (!IsWindows()) {
      return sys_msync(addr, size, flags);
    } else {
      return sys_msync_nt(addr, size, flags);
    }
  }
  