Developing a Python JIT and have trouble

Yuheng Zou zouyuheng1998 at gmail.com
Fri Mar 31 09:52:09 EDT 2017


I am building a Python JIT, so I want to change the interp->eval_frame to my own function.

I built a C++ library which contains EvalFrame function, and then use dlopen and dlsym to use it. It looks like this:

extern "C" PyObject *EvalFrame(PyFrameObject *f, int throwflag) {
    return _PyEval_EvalFrameDefault(f, throwflag);
}
I added following code to Python/pylifecycle.c at function _Py_InitializeEx_Private(Python version is 3.6.1):

void *pyjit = NULL;
pyjit = dlopen("../cmake-build-debug/libPubbon.dylib", 0);
if (pyjit != NULL) {
    interp->eval_frame = (_PyFrameEvalFunction)dlsym(pyjit, "EvalFrame");
    //interp->eval_frame = _PyEval_EvalFrameDefault;
} 
Then something strange happened. I used LLDB to trace the variables. When it ran at EvalFrame, the address of f pointer didn't change, but f->f_lineno changed.

Then when I ran python.exe, I got Segmentation Fault.

Why the address of the pointer didn't change, but the context change?

I am working on Mac OS X and Python 3.6.1. I want to know how to replace _PyEval_EvalFrameDefault in interp->eval_frame with my own function.


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