bin/47556: awk segfault: NULL dereference

[cheusov%tut.by@localhost]

>Number:         47556
>Category:       bin
>Synopsis:       awk segfault: NULL dereference
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Feb 10 23:40:01 +0000 2013
>Originator:     Aleksey Cheusov
>Release:        NetBSD 6.0_STABLE
>Organization:
>Environment:
        
        
System: NetBSD asrock.chizhovka.net 6.0_STABLE NetBSD 6.0_STABLE (GENERIC) #2: 
Sat Feb 9 16:41:02 FET 2013 
cheusov%asrock.chizhovka.net@localhost:/srv/obj/sys/arch/amd64/compile/GENERIC 
amd64
Architecture: x86_64
Machine: amd64
>Description:
strdup is given a NULL pointer.
Seen on awk from HEAD and netbsd-6.

core file and awk executable for NetBSD/x86-64 is here
http://mova.org/~cheusov/priv/awk_sigsegv.tar.bz2

#0  0x00007f7ff74db104 in strdup () from /usr/lib/libc.so.12
#1  0x000000000041602c in tostring (s=0x0) at 
/home/cheusov/prjs/nbawk/bin/../dist/tran.c:441
#2  0x0000000000415b09 in setsval (vp=0x7f7ff73dc280, s=0x0) at 
/home/cheusov/prjs/nbawk/bin/../dist/tran.c:361
#3  0x0000000000411d99 in instat (a=0x7f7ff6f5a5c8, n=288) at 
/home/cheusov/prjs/nbawk/bin/../dist/run.c:1478
#4  0x000000000040d5ab in execute (u=0x7f7ff6f5a3d0) at 
/home/cheusov/prjs/nbawk/bin/../dist/run.c:166
#5  0x0000000000411995 in ifstat (a=0x7f7ff6f5ab98, n=301) at 
/home/cheusov/prjs/nbawk/bin/../dist/run.c:1394
#6  0x000000000040d5ab in execute (u=0x7f7ff6f0a3a0) at 
/home/cheusov/prjs/nbawk/bin/../dist/run.c:166
#7  0x000000000040dcf7 in call (a=0x7f7ff6fb9b78, n=333) at 
/home/cheusov/prjs/nbawk/bin/../dist/run.c:289
#8  0x000000000040d5ab in execute (u=0x7f7ff6fb9b60) at 
/home/cheusov/prjs/nbawk/bin/../dist/run.c:166
#9  0x0000000000411a45 in whilestat (a=0x7f7ff6fb9ba8, n=342) at 
/home/cheusov/prjs/nbawk/bin/../dist/run.c:1411
#10 0x000000000040d5ab in execute (u=0x7f7ff6fb9b90) at 
/home/cheusov/prjs/nbawk/bin/../dist/run.c:166
#11 0x0000000000411995 in ifstat (a=0x7f7ff6fb9d28, n=301) at 
/home/cheusov/prjs/nbawk/bin/../dist/run.c:1394
#12 0x000000000040d5ab in execute (u=0x7f7ff7b44800) at 
/home/cheusov/prjs/nbawk/bin/../dist/run.c:166
#13 0x000000000040d689 in program (a=0x7f7ff6fdfb18, n=258) at 
/home/cheusov/prjs/nbawk/bin/../dist/run.c:189
#14 0x000000000040d5ab in execute (u=0x7f7ff6fdfb00) at 
/home/cheusov/prjs/nbawk/bin/../dist/run.c:166
#15 0x000000000040d497 in run (a=0x7f7ff6fdfb00) at 
/home/cheusov/prjs/nbawk/bin/../dist/run.c:141
#16 0x000000000040c915 in main (argc=5, argv=0x7f7fffffca90) at 
/home/cheusov/prjs/nbawk/bin/../dist/main.c:235
>How-To-Repeat:
original script and input data is rather big.
I hope core file is enough.
>Fix:
        

>Unformatted: