Does anybody know the meaning of compiler option -pthread for slapd?

[ynishimura@home.nimc.go.jp]

Dear sirs

I like to know the meaning of compile option -pthread in belows

gcc -g -O2 -I../../include -I../../include -DHAVE_CONFIG_H -L/root/openldap-1.2.
11/libraries -o slapd main.o daemon.o connection.o search.o filter.o add.o charr
ay.o attr.o entry.o config.o backend.o result.o operation.o dn.o compare.o modif
y.o delete.o modrdn.o ch_malloc.o value.o ava.o bind.o unbind.o abandon.o filter
entry.o phonetic.o acl.o str2filter.o aclparse.o init.o repl.o lock.o suffixalia
s.o schema.o schemaparse.o monitor.o configinfo.o version.o libbackends.a -lavl
-lldbm -lldif -lldap -llber -llthread -llutil -lcrypt -lutil -pthread

I am making an openldap box with PC running freebsd.
It doesn't have the support of shared library or something like that because it
has floppy version of freebsd and its freebsd is very small.

I succeeded in compiling, test and install openldap for ordinary freebsd PC.
Then I made slapd command compiled with -static option with gcc and it worked
with ordinary freebsd PC.
But, It could not work with floppy freebsd.

What does -pthread option of gcc means for kernel?

Sincerely
Y.NISHIMURA