gcc -pg is broken with threaded applications

[Sad Clouds <cryintothebluesky%googlemail.com@localhost>]

This is 5.1_STABLE amd64. Any ideas why threaded application crash like
this?

atom$ cat tmp.c
#include <pthread.h>

void *run(void *arg)
{
        pthread_detach(pthread_self());
}

int main(void)
{
        int i;
        pthread_t tid;

        for (i = 0; i < 8; i++)
        {
                pthread_create(&tid, NULL, &run, NULL);
        }

        pthread_exit(NULL);
}

atom$ gcc -pg -g3 -O1 tmp.c -lpthread
/usr/lib/libc.so.12: warning: warning: this program uses xdr_domainname
(), which is deprecated and buggy. /usr/lib/libc.so.12: warning:
warning: this program uses xdr_mapname(), which is deprecated and
buggy. /usr/lib/libc.so.12: warning: warning: this program uses
xdr_peername(), which is deprecated and buggy. 

atom$ ./a.out
a.out: _lwp_ctl: [1]   Segmentation fault (core dumped) ./a.out 

atom$ gdb ./a.out ./a.out.core GNU gdb 6.5
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details. This GDB was configured as "x86_64--netbsd"...
Reading symbols from /usr/lib/libpthread.so.0...done.
Loaded symbols for /usr/lib/libpthread.so.0
Reading symbols from /usr/lib/libc.so.12...done.
Loaded symbols for /usr/lib/libc.so.12
Reading symbols from /usr/libexec/ld.elf_so...done.
Loaded symbols for /usr/libexec/ld.elf_so
Core was generated by `a.out'.
Program terminated with signal 11, Segmentation fault.
#0  0x000000000041476c in choose_arena_hard ()
(gdb) where
#0  0x000000000041476c in choose_arena_hard ()
#1  0x00000000004158bc in imalloc ()
#2  0x0000000000415f13 in malloc ()
#3  0x000000000045c9f3 in _citrus_lookup_seq_open ()
#4  0x000000000045cbb4 in _citrus_lookup_simple ()
#5  0x0000000000443622 in catopen ()
#6  0x00000000004433b0 in strerror_r ()
#7  0x0000000000411b0d in strerror ()
#8  0x00000000004114fd in verr ()
#9  0x000000000041102e in err ()
#10 0x00007f7ffdc0b70f in pthread__init () from /usr/lib/libpthread.so.0
#11 0x0000000000433b38 in __libc_init ()
#12 0x000000000046502b in __do_global_ctors_aux ()
#13 0x000000000040fe3e in _init ()
#14 0x00007f7fffffd4f8 in ?? ()
#15 0x00000000004100e9 in ___start ()
#16 0x00007f7ffdffa000 in ?? ()
#17 0x0000000000000001 in ?? ()
#18 0x00007f7ffffff778 in ?? ()
#19 0x0000000000000000 in ?? ()
(gdb) q