1.Python/dynload_shlib.c:94: undefined reference to `dlsym’

to solve the problems such as under Ubuntu:

—————————————————————————————

Python/dynload_shlib.c:94: undefined reference to `dlsym’
dynload_shlib.c:130: undefined reference to `dlopen’
Python/dynload_shlib.c:141: undefined reference to `dlsym’
Python/dynload_shlib.c:133: undefined reference to `dlerror’

—————————————————————————————-

To solve this linking problem, run ‘python-config –libs’, then you got the dynamic library list. Find where these libs are, and add their paths to LD_LIBRARY_PATH before ‘scons ./build/ARM/gem5.opt’

Finally, it works!

2.PyImport_Import() fail:

如果python在编译安装的时候，没有使用:
./configure –enable-shared
那么就会造成在/usr/local/lib/目录下只有libpython2.7.a而没有libpython2.7.so，这个时候需要给makefile加一个参数:
C_FLAGS += -export-dynamic

或者重新使用./configure –enable-shared编译Python.

3.C/C++多线程调用Python

Python中有一个GIL，导致Python线程效率很低，此外若在C/C++中创建线程来调用Python解释器，会造成段错误。

解决方式：

//主线程中

Py_Initialize();

PyEval_InitThreads();
PyEval_ReleaseLock();   //启动子线程前执行，为了释放PyEval_InitThreads获得的全局锁，否则子线程可能无法获取到全局锁。

//子线程中

PyGILState_STATE state = PyGILState_Ensure();

…..    //调用Python代码

PyGILState_Release(state);

//主线程中

//保证子线程调用都结束后
PyGILState_Ensure();
Py_Finalize();
//之后不能再调用任何Python的API

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