Re: core dump for lack data of xticlabels()

[Ethan A M. <merritt@u.washington.edu>]

On Thursday 31 July 2008, Ethan A Merritt wrote:
> On Thursday 31 July 2008, Shigeharu TAKENO wrote:
> > shige 08/01 2008
> > ----------------
> > 
> > The gnuplot of current CVS version may make core dump by the 
> > following script which includes the lack data of xticlabels(), 
> > but gnuplot-4.2.3 may not:
> > 
> >  plot '-' using 1:2:xtic(3) w l
> >  1 2 tic1
> >  2 3 tic2
> >  3 6 
> >  4 4 tic4
> >  5 5 tic5
> >  e
> 
> Thank you for the bug report.
> 
> Rather than storing a NULL label and having to test for NULL every time
> the list of labels is scanned, I think it would be better not to store a
> NULL label at all.

Now I see there is a difference in the two fixes.  
One way writes a tic mark even if there is no label;
the other way writes neither a tic mark nor a label.

Normally I'd say that the user could catch the missing label and replace
it with "" if they wanted a tic mark. But unfortunately you can't trap the 
missing tic label from the command line.

gnuplot> plot 'xtic.dat' using 1:2:xtic(strcol(3)?strcol(3):"")
         non-integer passed to boolean operator

various other attempts at this cause various other error messages.

So it seems we have to choose either no tic, or a tic but no label.
I don't know which is likely to please more users.

[or I suppose we could teach the boolean operators that a NULL string
 is to be treated as FALSE].

	Ethan

> Something like this (not tested thorougly, but seems foolproof):
> 
> --- ../../gnuplot/src/axis.c	2008-06-05 21:15:58.000000000 -0700
> +++ ./axis.c	2008-07-31 21:39:09.000000000 -0700
> @@ -1618,6 +1618,9 @@ add_tic_user(AXIS_INDEX axis, char *label
>      struct ticmark *tic, *newtic;
>      struct ticmark listhead;
>  
> +    if (!label)
> +	return;
> +
>      /* Mark this axis as user-generated ticmarks only, unless the */
>      /* mix flag indicates that both user- and auto- tics are OK.  */
>      if (!axis_array[axis].ticdef.def.mix)
> 
> 
> 
> 
> >  OS: Solaris 9 (sparc)
> >  compiler: gcc-3.4.3 
> > 
> > The following patch seems to fix it.
> > 
> > ----- From here -----
> > --- axis.c.ORG	Fri Aug  1 12:20:48 2008
> > +++ axis.c	Fri Aug  1 13:03:09 2008
> > @@ -872,8 +872,12 @@
> >  	    if (!inrange(internal, internal_min, internal_max))
> >  		continue;
> >  
> > -	    if (mark->level < 0) /* label read from data file */
> > -		strncpy(label, mark->label, sizeof(label));
> > +	    if (mark->level < 0) {/* label read from data file */
> > +		if (mark->label != NULL) 
> > +		  strncpy(label, mark->label, sizeof(label));
> > +		else 
> > +		  label[0]='\0';
> > +	    }
> >  	    else if (axis_array[axis].is_timedata)
> >  		gstrftime(label, 24, mark->label ? mark->label : ticfmt[axis], mark->position);
> >  	    else
> > ----- To here -----
> > 
> > +========================================================+
> >  Shigeharu TAKENO     NIigata Institute of Technology
> >                        kashiwazaki,Niigata 945-1195 JAPAN
> >  sh...@ie...   TEL(&FAX): +81-257-22-8161
> > +========================================================+
> > 

-- 
Ethan A Merritt