linking c++ libraries on Linux

Question

I'm running the following command:

g++ -m32 testLogin.cpp  -L/root/c++/libs  -ldvrnetsdk -o testLoginO -lpthread  -lasound

the result:

/root/c++/libs/libdvrnetsdk.so: undefined reference to `snd_pcm_hw_params_set_channels'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `pthread_mutex_trylock'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `snd_pcm_readi'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `snd_pcm_hw_params_set_access'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `snd_strerror'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `pthread_mutexattr_settype'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `snd_pcm_hw_params_set_rate'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `snd_pcm_close'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `snd_pcm_hw_params_malloc'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `snd_pcm_hw_params_set_period_size'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `pthread_mutex_timedlock'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `pthread_mutexattr_destroy'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `snd_pcm_drain'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `snd_pcm_hw_params_free'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `pthread_create'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `snd_pcm_open'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `snd_pcm_hw_params_set_format'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `snd_pcm_writei'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `pthread_mutexattr_init'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `snd_pcm_hw_params'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `snd_pcm_hw_params_any'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `snd_pcm_prepare'
/root/c++/libs/libdvrnetsdk.so: undefined reference to `pthread_join'
collect2: error: ld returned 1 exit status

The first thing I did after this error was to include the libraries -lpthread -lasound, I also worked on the parameters order but did not work. I appriciate any help.

Libraries after code & objects. `-pthread` not `-lpthread`. – Mat Jan 10 '15 at 13:20 — Mat, Jan 10 '15 at 13:20

score 1 · Answer 1 · answered Jan 10 '15 at 13:22

1

did you try with just -pthread as the linker flag...sometimes it does notw ork with -lpthread...

This should work

g++ -m32 testLogin.cpp -L/root/c++/libs -ldvrnetsdk -pthread -lasound

answered Jan 10 '15 at 13:22

basav

1,475
12
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score 0 · Accepted Answer · edited May 23 '17 at 12:05

0

With gcc, ordering of linking does matter.

So, try with different order.

 g++ -m32 testLogin.cpp  -L/root/c++/libs -lpthread -lasound -ldvrnetsdk -o testLoginO

See this question for order: Why does the order in which libraries are linked sometimes cause errors in GCC?

Alternatively, you can use start-group option.

gcc -m32 testLogin.cpp  -L/root/c++/libs -Wl,--start-group -lpthread -lasound -ldvrnetsdk -Wl,--end-group -o testLoginO

Edit: As you still get the error, use nm on strings on your library and check if the symbols for which linker error is given are in the library or not. Check for library version. You might be on 64-bit kernel.

edited May 23 '17 at 12:05

Community

1
1

answered Jan 10 '15 at 13:32

doptimusprime

9,115
6
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90

tks! I used your second suggestion, with some modification: gcc -m32 -fuse-ld=bfd testLogin.cpp -L/root/c++/libs -Wl,--start-group -pthread -lasound -ldvrnetsdk -lstdc++ -Wl,--end-group -o testLoginO. It solved the pthread issue but I still have a undefined reference to `snd..." what I think is related to lasound library. Any clue? – Elmo Jan 10 '15 at 15:05

linking c++ libraries on Linux

2 Answers2