A simple example of how to reproduce the bug:

jose@linux:~> gnuplot

        G N U P L O T
        Version 4.0 patchlevel 0
        last modified Thu Apr 15 14:44:22 CEST 2004
        System: Linux 2.6.16-rc1-git3-4-default

        Copyright (C) 1986 - 1993, 1998, 2004
        Thomas Williams, Colin Kelley and many others

        This is gnuplot version 4.0.  Please refer to the documentation
        for command syntax changes.  The old syntax will be accepted
        throughout the 4.0 series, but all save files use the new syntax.

        Type `help` to access the on-line reference manual.
        The gnuplot FAQ is available from
                http://www.gnuplot.info/faq/

        Send comments and requests for help to
                <gnuplot-info@lists.sourceforge.net>
        Send bugs, suggestions and mods to
                <gnuplot-bugs@lists.sourceforge.net>


Terminal type set to 'x11'
gnuplot> x=1
gnuplot> plot(x)
*** buffer overflow detected ***: gnuplot_x11 terminated
======= Backtrace: =========
/lib/libc.so.6(__chk_fail+0x41)[0xb7da6241]
/lib/libc.so.6(__read_chk+0x50)[0xb7da6700]
gnuplot_x11[0x804b75f]
gnuplot_x11[0x8053485]
gnuplot_x11[0x805502f]
/lib/libc.so.6(__libc_start_main+0xd8)[0xb7ceb808]
gnuplot_x11[0x804a4c1]
======= Memory map: ========
08048000-08059000 r-xp 00000000 03:02 326480     /usr/lib/gnuplot/4.0/gnuplot_x11
08059000-0805b000 rw-p 00010000 03:02 326480     /usr/lib/gnuplot/4.0/gnuplot_x11
0805b000-080a0000 rw-p 0805b000 00:00 0          [heap]
b7c9d000-b7ca7000 r-xp 00000000 03:02 1084970    /lib/libgcc_s.so.1
b7ca7000-b7ca8000 rw-p 00009000 03:02 1084970    /lib/libgcc_s.so.1
b7ca8000-b7cac000 r-xp 00000000 03:02 995153     /usr/X11R6/lib/libXfixes.so.3.0
b7cac000-b7cad000 rw-p 00003000 03:02 995153     /usr/X11R6/lib/libXfixes.so.3.0
b7cad000-b7cba000 r-xp 00000000 03:02 995151     /usr/X11R6/lib/libXext.so.6.4
b7cba000-b7cbb000 rw-p 0000c000 03:02 995151     /usr/X11R6/lib/libXext.so.6.4
b7cd0000-b7cd2000 rw-p b7cd0000 00:00 0
b7cd2000-b7cd4000 r-xp 00000000 03:02 1084940    /lib/libdl-2.3.90.so
b7cd4000-b7cd6000 rw-p 00001000 03:02 1084940    /lib/libdl-2.3.90.so
b7cd6000-b7df0000 r-xp 00000000 03:02 1084934    /lib/libc-2.3.90.so
b7df0000-b7df2000 r--p 00119000 03:02 1084934    /lib/libc-2.3.90.so
b7df2000-b7df4000 rw-p 0011b000 03:02 1084934    /lib/libc-2.3.90.so
b7df4000-b7df7000 rw-p b7df4000 00:00 0
b7df7000-b7e1a000 r-xp 00000000 03:02 1084942    /lib/libm-2.3.90.so
b7e1a000-b7e1c000 rw-p 00022000 03:02 1084942    /lib/libm-2.3.90.so
b7e1c000-b7f10000 r-xp 00000000 03:02 995127     /usr/X11R6/lib/libX11.so.6.2
b7f10000-b7f13000 rw-p 000f4000 03:02 995127     /usr/X11R6/lib/libX11.so.6.2
b7f14000-b7f1b000 r-xp 00000000 03:02 995175     /usr/X11R6/lib/libXrender.so.1.2.2
b7f1b000-b7f1c000 rw-p 00006000 03:02 995175     /usr/X11R6/lib/libXrender.so.1.2.2
b7f1c000-b7f24000 r-xp 00000000 03:02 995143     /usr/X11R6/lib/libXcursor.so.1.0.2
b7f24000-b7f25000 rw-p 00007000 03:02 995143     /usr/X11R6/lib/libXcursor.so.1.0.2
b7f25000-b7f27000 r-xp 00000000 03:02 1052617    /usr/X11R6/lib/X11/locale/lib/common/xlcDef.so.2
b7f27000-b7f28000 rw-p 00001000 03:02 1052617    /usr/X11R6/lib/X11/locale/lib/common/xlcDef.so.2
b7f28000-b7f29000 rw-p b7f28000 00:00 0
b7f29000-b7f43000 r-xp 00000000 03:02 1084927    /lib/ld-2.3.90.so
b7f43000-b7f45000 rw-p 00019000 03:02 1084927    /lib/ld-2.3.90.so
bf9d4000-bf9ea000 rw-p bf9d4000 00:00 0          [stack]
ffffe000-fffff000 ---p 00000000 00:00 0          [vdso]