Hi!
On Tue, Dec 13, 2022 at 10:37:12PM +0000, Harald van Dijk wrote:
> On 13/12/2022 22:17, наб wrote:
> > Reading the standard input byte-by-byte is the obvious solution to this
> > issue, Just Works, and is how all other shells do it (we could,
> > theoretically, read regular files block-wise, then seek within them after
> > parsing, but the complexity out-weighs the rarity of running
> > sh < program; we could also do whole-line reads on teletypes in
> > icanon mode, but, again, the gain here is miniscule for an interactive
> > session, and the teletype mode can change at any time, so...).
> > Naturally, we keep reading block-wise for non-standard-input.
> There are a few things to consider here:
> - Not all shells do it this way. bash does do the block-wise read,
> followed by a seek, when stdin is seekable. While I agree that it is
> not necessary and not worth it, you specifically say that other shells
> do not do this. That's simply not true.
Yeah, I wrote the parenthetical way after the rest and didn't think to
reassess them in consort (it appears that ksh93 seeks, zsh doesn't).
> - This patch breaks internal assumptions in dash that the buffer will
> contain a full line, affecting error recovery. See below.
> > --- a/src/input.c
> > +++ b/src/input.c
> > @@ -195,7 +195,7 @@ retry:
> > } else
> > #endif
> > - nr = read(parsefile->fd, buf, IBUFSIZ - 1);
> > + nr = read(parsefile->fd, buf, parsefile->fd == 0 ? 1 : IBUFSIZ - 1);
> > if (nr < 0) {
>
> With dash 0.5.12:
>
> $ | echo bug
> src/dash: 1: Syntax error: "|" unexpected
> $
>
> With dash 0.5.12 + your patch:
>
> $ | echo bug
> src/dash: 1: Syntax error: "|" unexpected
> $ bug
> $
>
> I had implemented the same change in my fork, see <https://github.com/hvdijk/gwsh/commit/d279523041c1c380d64b6dec7760feba20bbf6b5>
> for the additional changes I needed to get everything working.
It's interesting to see that the line error bug appears to blame back to
start-of-git(?), and the partial line consumption is triggerable ‒
with vastly more pathological input, admittedly ‒ on unpatched dash as
well. I've imported the other fixes piece-meal, and the updated
series (in follow-up), passes all cases in your commit message as well.
Best,
наб
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