c - 为什么我得到对 pthread_mutexattr_settype 的 undefined reference ？

Question

我正在尝试从 Novell LDAP C SDK 编译和链接示例文件，但由于 pthread 库中有 3 个未解析的符号，链接失败。我在 Ubuntu 13.10 (Saucy) 上使用 gcc 4.8.1。我已将 pthread 库作为命令行中的最后一个库正确包含在内，但这些特定符号仍未解析。

$ gcc -Wl,-trace-symbol=pthread_mutexattr_settype -Wl,-trace-symbol=pthread_mutexattr_init   -Wl,-trace-symbol=pthread_mutex_trylock  -o search search.o -L../lib -lldapsdk -lpthread

../lib/libldapsdk.so: reference to pthread_mutexattr_settype<br>
../lib/libldapsdk.so: reference to pthread_mutexattr_init<br>
../lib/libldapsdk.so: reference to pthread_mutex_trylock<br>
/lib/i386-linux-gnu/libpthread.so.0: definition of pthread_mutexattr_settype<br>
/lib/i386-linux-gnu/libpthread.so.0: definition of pthread_mutexattr_init<br>
/lib/i386-linux-gnu/libpthread.so.0: definition of pthread_mutex_trylock<br>
../lib/libldapsdk.so: undefined reference to pthread_mutexattr_settype<br>
../lib/libldapsdk.so: undefined reference to pthread_mutex_trylock<br>
../lib/libldapsdk.so: undefined reference to pthread_mutexattr_init<br>
collect2: error: ld returned 1 exit status

$ readelf --all  /lib/i386-linux-gnu/libpthread.so.0|grep pthread_mutexattr_settype<br>
   114: 00009d90    36 FUNC    GLOBAL DEFAULT   13 pthread_mutexattr_settype@@GLIBC_2.1<br>
   493: 00009d90    36 FUNC    GLOBAL DEFAULT   13 pthread_mutexattr_settype

Answer 1

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请将-pthread 传递给编译器(不带-l)。另见 gcc - significance of -pthread flag when compiling .