在Python中加載共享庫時未定義符號

Question

我嘗試在某些python代碼中使用C ++編寫的共享庫。 我在Linux OS下。

首先，我使用以下命令創建共享庫：

g++ -Wall -fPIC -O2 -c HeliosDacAPI.cpp
g++ -shared -o libHeliosDacAPI.so HeliosDacAPI.o

然后，我嘗試在python控制台中加載此庫：

>>> import ctypes
>>> HeliosLib = ctypes.cdll.LoadLibrary("./libHeliosDacAPI.so")

我收到一個錯誤：

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.5/ctypes/__init__.py", line 425, in LoadLibrary
    return self._dlltype(name)
  File "/usr/lib/python3.5/ctypes/__init__.py", line 347, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: ./libHeliosDacAPI.so: undefined symbol: _ZN9HeliosDac18GetControlResponseEiPhi

---

這是HeliosDacAPI.h

nm libHeliosDacAPI.so顯示：

0000000000202088 B __bss_start
0000000000202088 b completed.7585
                 w __cxa_finalize@@GLIBC_2.2.5
0000000000202090 B dacController
0000000000000cb0 t deregister_tm_clones
0000000000000d40 t __do_global_dtors_aux
0000000000201dd8 t __do_global_dtors_aux_fini_array_entry
0000000000202078 d __dso_handle
0000000000202080 d DW.ref.__gxx_personality_v0
0000000000201de8 d _DYNAMIC
0000000000202088 D _edata
00000000002020a0 B _end
00000000000014b8 T _fini
0000000000000d80 t frame_dummy
0000000000201dd0 t __frame_dummy_init_array_entry
0000000000001758 r __FRAME_END__
0000000000202000 d _GLOBAL_OFFSET_TABLE_
                 w __gmon_start__
00000000000014dc r __GNU_EH_FRAME_HDR
                 U __gxx_personality_v0@@CXXABI_1.3
0000000000000bb0 T _init
0000000000202098 B inited
                 w _ITM_deregisterTMCloneTable
                 w _ITM_registerTMCloneTable
0000000000201de0 d __JCR_END__
0000000000201de0 d __JCR_LIST__
                 w _Jv_RegisterClasses
                 U __printf_chk@@GLIBC_2.3.4
0000000000000cf0 t register_tm_clones
                 U __stack_chk_fail@@GLIBC_2.4
0000000000202088 d __TMC_END__
                 U _Unwind_Resume@@GCC_3.0
0000000000001230 T _Z10SetShutterib
0000000000000db0 T _Z10WriteFrameiihP11HeliosPointi
0000000000001420 T _Z11OpenDevicesv
00000000000013d0 T _Z12CloseDevicesv
0000000000001360 T _Z13EraseFirmwarei
0000000000001290 T _Z18GetFirmwareVersioni
0000000000000f20 T _Z4Stopi
0000000000000f90 T _Z7GetNameiPc
00000000000010c0 T _Z7SetNameiPc
0000000000001150 T _Z9GetStatusi
                 U _ZdlPv@@GLIBCXX_3.4
                 U _ZN9HeliosDac11OpenDevicesEv
                 U _ZN9HeliosDac11SendControlEiPhi
                 U _ZN9HeliosDac18GetControlResponseEiPhi
                 U _ZN9HeliosDac9SendFrameEiPhi
                 U _ZN9HeliosDacC1Ev
                 U _ZN9HeliosDacD1Ev
                 U _Znwm@@GLIBCXX_3.4

我正在尋找有關如何調試此類問題的提示。

Answer 1

我不確定，但是似乎HeliosDac::GetControlResponse(int, ?*, int)中定義了HeliosDac.cpp HeliosDac::GetControlResponse(int, ?*, int) ，您沒有編譯並鏈接到libHeliosDacAPI.so 。

的確，從nm libHeliosDacAPI.so我們清楚地看到，這個符號使用，但U ndefined（這意味着你的問題不是來自你的方式來加載在Python庫）：

                 U _ZN9HeliosDac18GetControlResponseEiPhi

您可以嘗試使用：

g++ -Wall -fPIC -O2 -c HeliosDacAPI.cpp
g++ -Wall -fPIC -O2 -c HeliosDac.cpp
g++ -shared -lusb -o libHeliosDacAPI.so HeliosDacAPI.o HeliosDac.o