Question

When i compile example of interoperation between C and erlang with next command:

gcc -o fac -I/usr/local/lib/erlang/lib/erl_interface-3.5.9/include \
-L/usr/local/lib/erlang/lib/erl_interface-3.5.9/lib fac.c -lerl_interface -lei

My system is Ubuntu. I got next errors:

/usr/lib/libei.a(ei_pthreads.o): In function __erl_errno_place':
(.text+0x4c): undefined reference topthread_once’
/usr/lib/libei.a(ei_pthreads.o): In function __erl_errno_place':
(.text+0x7a): undefined reference topthread_getspecific’
/usr/lib/libei.a(ei_pthreads.o): In function __erl_errno_place':
(.text+0xa2): undefined reference topthread_setspecific’
/usr/lib/libei.a(ei_pthreads.o): In function __erl_errno_place':
(.text+0xb4): undefined reference topthread_getspecific’
/usr/lib/libei.a(ei_pthreads.o): In function erl_errno_key_alloc':
(.text+0x136): undefined reference topthread_key_create’
/usr/lib/libei.a(ei_pthreads.o): In function ei_m_trylock':
(.text+0x189): undefined reference topthread_mutex_trylock’
collect2: ld returned 1 exit status

Any suggestions?

Answer 1

You need to link pthread library. Try:
gcc -o fac -I/usr/local/lib/erlang/lib/erl_interface-3.5.9/include -L/usr/local/lib/erlang/lib/erl_interface-3.5.9/lib fac.c -lerl_interface -lei -lpthread
Hope this helps!