libpthread.so.0: error adding symbols: DSO missing from command line

Question

When I\'m compiling openvswitch-1.5.0, I\'ve encountered the following compile error:

 gcc -Wstrict-prototypes -Wall -Wno-sign-compare -Wpointer-arith
     -         


        

Answer 1

If using g++, make sure that you are not running gcc instead

Answer 2

You should mention the library on the command line after the object files being compiled:

 gcc -Wstrict-prototypes -Wall -Wno-sign-compare -Wpointer-arith -Wdeclaration-after-statement -Wformat-security -Wswitch-enum -Wunused-parameter -Wstrict-aliasing -Wbad-function-cast -Wcast-align -Wstrict-prototypes -Wold-style-definition -Wmissing-prototypes -Wmissing-field-initializers -Wno-override-init \
     -g -O2 -export-dynamic -o utilities/ovs-dpctl utilities/ovs-dpctl.o \
     lib/libopenvswitch.a \
     /home/jyyoo/src/dpdk/build/lib/librte_eal.a /home/jyyoo/src/dpdk/build/lib/libethdev.a /home/jyyoo/src/dpdk/build/lib/librte_cmdline.a /home/jyyoo/src/dpdk/build/lib/librte_hash.a /home/jyyoo/src/dpdk/build/lib/librte_lpm.a /home/jyyoo/src/dpdk/build/lib/librte_mbuf.a /home/jyyoo/src/dpdk/build/lib/librte_ring.a /home/jyyoo/src/dpdk/build/lib/librte_mempool.a /home/jyyoo/src/dpdk/build/lib/librte_malloc.a \
     -lrt -lm -lpthread 

Explanation: the linking is dependent on the order of modules. Symbols are first requested, and then linked in from a library that has them. So you have to specify modules that use libraries first, and libraries after them. Like this:

gcc x.o y.o z.o -la -lb -lc

Moreover, in case there's a circular dependency, you should specify the same library on the command line several times. So in case libb needs symbol from libc and libc needs symbol from libb, the command line should be:

gcc x.o y.o z.o -la -lb -lc -lb