Re: [BUG] readline history

From: Alexander Aring <alex.aring@gmail.com>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: barebox@lists.infradead.org
Subject: Re: [BUG] readline history
Date: Mon, 1 Sep 2014 10:44:57 +0200	[thread overview]
Message-ID: <20140901084455.GA8561@omega> (raw)
In-Reply-To: <20140901083033.GF5352@pengutronix.de>

Hi Sascha,

On Mon, Sep 01, 2014 at 10:30:33AM +0200, Sascha Hauer wrote:
> Hi Teresa,
> 
> On Thu, Aug 28, 2014 at 09:50:05AM +0200, Teresa Gamez wrote:
> > Hello Sascha,
> > 
> > I noticed a bug on the latest master.
> > When no history is present and I hit the arrow up key, I get:
> > 
> > unable to handle NULL pointer dereference at address 0x00000001
> > pc : [<9fe243ba>]    lr : [<9fe268cf>]
> > sp : 9ffff9d0  ip : 00000016  fp : 00000002
> > r10: 00000001  r9 : 9fe549dc  r8 : 9fe65d08
> > r7 : 00000400  r6 : 00000001  r5 : 00000000  r4 : 9fe66258
> > r3 : 00000000  r2 : 00000000  r1 : 00000001  r0 : 9fe66258
> > Flags: nZCv  IRQs off  FIQs on  Mode SVC_32
> > [<9fe243ba>] (strcpy+0xa/0xe) from [<9fe268cf>] (readline+0x363/0x4e0)
> > [<9fe268cf>] (readline+0x363/0x4e0) from [<9fe05469>] (file_get
> > +0x49/0x110)
> > 
> > I could bisect it to this commit:
> > 
> > 
> > ada160a34a1ec8421d5bb7b9dd746294668a5130 is the first bad commit
> > commit ada160a34a1ec8421d5bb7b9dd746294668a5130
> > Author: Sascha Hauer <s.hauer@pengutronix.de>
> > Date:   Tue Jul 29 11:54:26 2014 +0200
> 
> Damned. While working on that patch I had exactly this problem and
> thought I tested this case. Apparantly I didn't :(
> 
> The following should fix this:
> 
> Sascha
> 
> From 7fd0d972f71610c25276ca387164b1fd71fb74be Mon Sep 17 00:00:00 2001
> From: Sascha Hauer <s.hauer@pengutronix.de>
> Date: Mon, 1 Sep 2014 10:21:44 +0200
> Subject: [PATCH] readline: Fix history prev when history is empty
> 
> We cannot use list_entry() on an empty list. Without history
> we have to return an empty line. This fixes a crash when the
> cursor up button is pressed and no command has been entered
> previously. Broken since:
> 
> commit ada160a34a1ec8421d5bb7b9dd746294668a5130
> Author: Sascha Hauer <s.hauer@pengutronix.de>
> Date:   Tue Jul 29 11:54:26 2014 +0200
> 
>     readline: reimplement history functions
> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> Reported-by: Teresa Gamez <t.gamez@phytec.de>
> ---
>  lib/readline.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/lib/readline.c b/lib/readline.c
> index b70bca8..e855abd 100644
> --- a/lib/readline.c
> +++ b/lib/readline.c
> @@ -68,6 +68,9 @@ static const char *hist_prev(void)
>  	struct history *history;
>  
>  	if (history_current->prev == &history_list) {
> +		if (list_empty(&history_list))
> +			return "";
> +

what's about to ring the terminal bell when this happen?

- Alex

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