text: /*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
  │vi: set net ft=c ts=8 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/errno.h"
  #include "libc/mem/mem.h"
  #include "libc/runtime/runtime.h"
  #include "libc/stdio/internal.h"
  #include "libc/stdio/stdio.h"
  
  /**
   * Closes standard i/o stream and its underlying thing.
   *
   * @param f is the file object, which is always free if it's heap,
   *     otherwise its resources are released and fields updated
   * @return 0 on success or -1 on error, which can be a trick for
   *     differentiating between EOF and real errors during previous
   *     i/o calls, without needing to call ferror()
   * @see fclose_s()
   */
  int fclose(FILE *f) {
    int rc;
    if (!f) return 0;
    __fflush_unregister(f);
    fflush(f);
    if (!f->nofree) {
      free_s(&f->buf);
    }
    f->state = EOF;
    if (f->noclose) {
      f->fd = -1;
    } else if (close_s(&f->fd) == -1) {
      f->state = errno;
    }
    if (f->state == EOF) {
      rc = 0;
    } else {
      errno = f->state;
      rc = EOF;
    }
    free_s(&f);
    return rc;
  }
  