Cross-compiling

when cross-compiling demos of sdl for uclinux,
if using the option --enable-pth --enable-pthread
there is a error as follows:

…/lib/libpthread.a(signals.o):In function ‘raise’:
signals.o(.text+0xa24):multiple definition of ‘raise’
…/lib/libc.a(raise.o)(.text+0x0): first defined here

why does the error come into being then?

Regards,
Andy