Bug 17765

There have been some recent changes to /bin/sh. I have observed
the above error message with a shell script that ran fine before.

Fix: 

Unknown. If you want me to test something or have some fix, tell me.
How-To-Repeat: 
Until now, I observed the errorneous behaviour only with this special
shell script. I won't post it here since it is quite long and will
only run in my environment. However, if someone ist still interested
in it, please let me now and I will send it in private mail.

I have compiled sh with -g and ran the script within it and gdb:

root@bali:/people/andre/x>gdb ./sh
GNU gdb 4.18
Copyright 1998 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i386-unknown-freebsd"...
(gdb) set args ./csf cu pr se ba
(gdb) run
Starting program: ./sh ./csf cu pr se ba

checking hosts:....
unreachable: none
targets: 4


Files in /server/FreeBSD/conf/3/curry:
-----------------------------------------------------------------------
sh in free(): warning: junk pointer, too low to make sense.

Program received signal SIGSEGV, Segmentation fault.
popstackmark (mark=0xbfbfd6e0) at /src/src-3/bin/sh/memalloc.c:191
191                     stackp = sp->prev;
(gdb) where
#0  popstackmark (mark=0xbfbfd6e0) at /src/src-3/bin/sh/memalloc.c:191
#1  0x804b069 in evalfor (n=0x80ac948) at /src/src-3/bin/sh/eval.c:364
#2  0x804ad76 in evaltree (n=0x80ac948, flags=0)
    at /src/src-3/bin/sh/eval.c:251
#3  0x804ad54 in evaltree (n=0x80acd64, flags=0)
    at /src/src-3/bin/sh/eval.c:241
#4  0x804ac2b in evaltree (n=0x80acdc4, flags=0)
    at /src/src-3/bin/sh/eval.c:203
#5  0x804ad54 in evaltree (n=0x80ac558, flags=0)
    at /src/src-3/bin/sh/eval.c:241
#6  0x804ad54 in evaltree (n=0x80acdd4, flags=0)
    at /src/src-3/bin/sh/eval.c:241
#7  0x804ac2b in evaltree (n=0x80ace50, flags=0)
    at /src/src-3/bin/sh/eval.c:203
#8  0x804ac2b in evaltree (n=0x80acf28, flags=0)
    at /src/src-3/bin/sh/eval.c:203
#9  0x804ac2b in evaltree (n=0x80ae760, flags=0)
    at /src/src-3/bin/sh/eval.c:203
#10 0x804ac2b in evaltree (n=0x80ae7c0, flags=0)
    at /src/src-3/bin/sh/eval.c:203
#11 0x804ac2b in evaltree (n=0x80ae824, flags=0)
    at /src/src-3/bin/sh/eval.c:203
#12 0x804ac2b in evaltree (n=0x80ae8fc, flags=0)
    at /src/src-3/bin/sh/eval.c:203
#13 0x804ac2b in evaltree (n=0x80af128, flags=0)
    at /src/src-3/bin/sh/eval.c:203
#14 0x804ac2b in evaltree (n=0x80af188, flags=0)
    at /src/src-3/bin/sh/eval.c:203
#15 0x804afe2 in evalfor (n=0x80a55ec) at /src/src-3/bin/sh/eval.c:351
#16 0x804ad76 in evaltree (n=0x80a55ec, flags=0)
    at /src/src-3/bin/sh/eval.c:251
#17 0x805266b in cmdloop (top=1) at /src/src-3/bin/sh/main.c:254
#18 0x8052583 in main (argc=6, argv=0xbfbfd904) at /src/src-3/bin/sh/main.c:203
#19 0x80480ed in _start ()