On my Rawhide 20000811 system, fetchmail-5.4.3-4 segfaults under
runsocks-1.0r10-5.
Downgrading to fetchmail-5.3.0-1 solves the problem.  I notice that going
from fetchmail-5.3 to
fetchmail-5.4,  additional crypto libraries are used, including kerberos;
not sure if that's relevant.

This could very well be a runsocks problem, though I haven't had problems
using runsocks-1.0r10-5
with other apps, including telnet and cvs.

More details:

dunwoody2:/1> rpm -q runsocks
runsocks-1.0r10-5
dunwoody2:/1> rpm -q fetchmail
fetchmail-5.3.0-1
dunwoody2:/1> cat .fetchmailrc
set postmaster "dunwoody"
set daemon 60
poll 24.0.0.70 with proto POP3
user "dunwoody" there with password "*****" is dunwoody here options
fetchall
dunwoody2:/1> ldd /usr/bin/fetchmail
	libcrypt.so.1 => /lib/libcrypt.so.1 (0x4001d000)
	libresolv.so.2 => /lib/libresolv.so.2 (0x4004a000)
	libc.so.6 => /lib/libc.so.6 (0x4005c000)
	/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
dunwoody2:/1> runsocks fetchmail -vN
fetchmail: starting fetchmail 5.3.0 daemon 
fetchmail: 5.3.0 querying 24.0.0.70 (protocol POP3) at Tue, 12 Sep 2000
17:19:08 -0700 (PDT)
fetchmail: POP3< +OK InterMail POP3 server ready.
fetchmail: POP3> USER dunwoody
fetchmail: POP3< +OK please send PASS command
fetchmail: POP3> PASS *
fetchmail: POP3< +OK dunwoody is welcome here
fetchmail: POP3> STAT
fetchmail: POP3< +OK 0 0
fetchmail: No mail for dunwoody at 24.0.0.70
fetchmail: POP3> QUIT
fetchmail: POP3< +OK dunwoody InterMail POP3 server signing off.
fetchmail: fetchmail: sleeping at Tue, 12 Sep 2000 17:19:11 -0700 (PDT)
^C
fetchmail: terminated with signal 2
dunwoody2:/1> ... rpm -Uvh /1/pkg/nrpm/fetchmail-5.4.3-4.i386.rpm 
fetchmail                  
##################################################
dunwoody2:/1> ldd /usr/bin/fetchmail
	libkrb4.so.2 => /usr/kerberos/lib/libkrb4.so.2 (0x4001d000)
	libdes425.so.3 => /usr/kerberos/lib/libdes425.so.3 (0x40034000)
	libcrypt.so.1 => /lib/libcrypt.so.1 (0x40039000)
	libresolv.so.2 => /lib/libresolv.so.2 (0x40066000)
	libkrb5.so.3 => /usr/kerberos/lib/libkrb5.so.3 (0x40078000)
	libk5crypto.so.3 => /usr/kerberos/lib/libk5crypto.so.3 (0x400e0000)
	libcom_err.so.3 => /usr/kerberos/lib/libcom_err.so.3 (0x400f5000)
	libgssapi_krb5.so.2 => /usr/kerberos/lib/libgssapi_krb5.so.2 (0x400f7000)
	libc.so.6 => /lib/libc.so.6 (0x4010c000)
	/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
dunwoody2:/1> runsocks fetchmail -vN
Segmentation fault
dunwoody2:/1> fetchmail -vN
fetchmail: starting fetchmail 5.4.3 daemon 
fetchmail: 5.4.3 querying 24.0.0.70 (protocol POP3) at Tue, 12 Sep 2000
17:22:22 -0700 (PDT)
fetchmail: Query status=2 (SOCKET)
fetchmail: fetchmail: sleeping at Tue, 12 Sep 2000 17:22:25 -0700 (PDT)
^C
fetchmail: terminated with signal 2
dunwoody2:/1> export LD_PRELOAD=libsocks5_sh.so
dunwoody2:/1> gdb /usr/bin/fetchmail
GNU gdb 5.0
Copyright 2000 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-redhat-linux"...
(no debugging symbols found)...
(gdb) r -vN
Starting program: /usr/bin/fetchmail -vN

Program received signal SIGSEGV, Segmentation fault.
0x40023836 in HostentCopy () from /usr/lib/libsocks5_sh.so
(gdb) bt
#0  0x40023836 in HostentCopy () from /usr/lib/libsocks5_sh.so
#1  0x40023be0 in gethostbyname () from /usr/lib/libsocks5_sh.so
#2  0x8052b77 in strcpy () at ../sysdeps/generic/strcpy.c:31
#3  0x8050f39 in strcpy () at ../sysdeps/generic/strcpy.c:31
#4  0x40146665 in __libc_start_main (main=0x8050d80 <strcpy+26060>, argc=2, 
    ubp_av=0xbffffac4, init=0x8049e64, fini=0x806283c <strcpy+98440>, 
    rtld_fini=0x4000dca4 <_dl_fini>, stack_end=0xbffffabc)
    at ../sysdeps/generic/libc-start.c:111
(gdb) q
The program is running.  Exit anyway? (y or n) y
dunwoody2:/1>