Re: segfault in plot3d

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

On Tuesday 17 February 2009, James R. Van Zandt wrote:
> 
> I ran across a reliable segfault with the splot command, with the
> current CVS code:

There is now a fix for this problem in CVS.

	Ethan



> 
>         G N U P L O T
>         Version 4.3 patchlevel 0
>         last modified February 2009
> 
> In particular, this is *without* my proposed changes to fit.c
> 
> Here's a run under the debugger:
> 
> gnuplot> splot 'lin2.dat',x+y
> [New Thread 0xb7843a40 (LWP 27810)]
> 
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 0xb7843a40 (LWP 27810)]
> calculate_set_of_isolines (value_axis=FIRST_Z_AXIS, cross=false, this_iso=0xbffb32e0, iso_axis=FIRST_Y_AXIS, iso_min=2, iso_step=0.33333333333333331, num_iso_to_use=10, sam_axis=FIRST_X_AXIS, sam_min=1, sam_step=0.030303030303030304, num_sam_to_use=100, need_palette=false) at plot3d.c:1174
> (gdb) backtrace
> #0  calculate_set_of_isolines (value_axis=FIRST_Z_AXIS, cross=false, this_iso=0xbffb32e0, iso_axis=FIRST_Y_AXIS, iso_min=2, iso_step=0.33333333333333331, num_iso_to_use=10, sam_axis=FIRST_X_AXIS, sam_min=1, sam_step=0.030303030303030304, num_sam_to_use=100, need_palette=false) at plot3d.c:1174
> #1  0x080a808c in plot3drequest () at plot3d.c:1909
> #2  0x080571d7 in do_line () at command.c:595
> #3  0x0805796d in com_line () at command.c:338
> #4  0x0809a6dd in main (argc=1, argv=0xbffb35a4) at plot.c:659
> (gdb) 
> 
> Here's lin2.dat:
> ---------------------------------------------
> #octave:9> for x=[1:4];for y=[2:5]; fprintf('%f %f %f 1\n',x,y,10*x+2*y+randn);end;end
> 1.000000 2.000000 13.753875 1
> 1.000000 3.000000 15.843192 1
> 1.000000 4.000000 17.752269 1
> 1.000000 5.000000 18.819627 1
> 
> 
> 2.000000 2.000000 25.480149 1
> 2.000000 3.000000 26.217588 1
> 2.000000 4.000000 28.555638 1
> 2.000000 5.000000 30.757950 1
> 
> 
> 3.000000 2.000000 33.879955 1
> 3.000000 3.000000 36.190724 1
> 3.000000 4.000000 39.199289 1
> 3.000000 5.000000 40.153219 1
> 
> 
> 4.000000 2.000000 43.413695 1
> 4.000000 3.000000 45.938903 1
> 4.000000 4.000000 49.196757 1
> 4.000000 5.000000 50.136290 1
> #octave:10> diary off
> -----------------------------------------
> 
> 
> All these commands work fine:
> 
>    gnuplot> splot 'fit2.dat'
>    gnuplot> splot x+y
>    gnuplot> splot x+y,'fit2.dat'
> 
> It only fails when plotting the data file first, then the function.
> I've had other data files fail, but demo/glasses.dat succeeds.
> 
> I set a breakpoint at plot3d.c:1174 in calculate_set_of_isolines() and
> followed execution.  When j=0 and i=99, the function reaches end of
> the linked list, sets this_iso to zero, then sets points to zero.  The
> next time through when j=1 and i=0, the function dies trying to access
> points[i].x.  I haven't been able to identify the cause.
> 
> I have a couple of other binaries installed.
> This version also crashes:
>         G N U P L O T
>         Version 4.3 patchlevel 0
>         last modified January 2007
> 
> This version is okay:
>         G N U P L O T
>         Version 4.2 patchlevel 4 
>         last modified Sep 2008
> 
> 
> Does anyone else see this?
> 
>      - Jim Van Zandt
> 


-- 
Ethan A Merritt