Re: Coreutils 5.0.91: Fix crash in head/tail

[Jim Meyering]

Paul Eggert <address@hidden> wrote:
> Andreas Schwab <address@hidden> writes:
>
>> tail crashes on read failures, like trying to read from a directory.
>> head has the same bug, but it is harder to trigger.
>
> Thanks for catching that.  Here's a proposed improvement on your
> patch, which avoids an unnecessary assignment to tmp->nbytes.

Thanks for the clean-up, but isn't that assignment to tmp->nbytes
necessary.  There are uses after the main while loop, and I seem to
recall wanting to make the same change but not being able to.

...
> @@ -496,9 +494,10 @@ elide_tail_lines_pipe (const char *filen
>       n_elide newlines, or until EOF, whichever comes first.  */
>    while (1)
>      {
> -      n_read = tmp->nbytes = safe_read (fd, tmp->buffer, BUFSIZ);
> +      n_read = safe_read (fd, tmp->buffer, BUFSIZ);
>        if (n_read == 0 || n_read == SAFE_READ_ERROR)
>       break;
> +      tmp->nbytes = n_read;
>        tmp->nlines = 0;
>        tmp->next = NULL;
>