Re: [BUG] readline history

[Sascha Hauer <s.hauer@pengutronix.de>]

On Mon, Sep 01, 2014 at 10:44:57AM +0200, Alexander Aring wrote:
> 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?

I added a getcmd_cbeep() to add the beep.

Sascha

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