在Linux上链接c++库

Question

我正在运行以下命令：

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

结果：

/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

在此错误发生后，我做的第一件事是包含库-lpthread -lasound，我也处理参数顺序，但没有工作。我相信任何帮助。

Answer 1

对于gcc来说，联系的顺序很重要。

所以，试着用不同的顺序。

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

有关顺序，请参阅此问题：Why does the order in which libraries are linked sometimes cause errors in GCC?

或者，您可以使用“开始组”选项。

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

编辑:当您仍然得到错误时，请在库中的字符串上使用nm，并检查链接器错误所在的符号是否在库中。检查库版本。你可能在64位内核上。

Answer 2

你试过用-pthread作为链接器flag...sometimes吗？

这应该能行

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