Python C API - 停止执行(稍后继续) [英] Python C API - Stopping Execution (and continuing it later)

问题描述

1) 当 Python 解释器从特定函数返回时，我想使用 Python C API 中的分析函数来捕获它.

1) I would like to use the profiling functions in the Python C API to catch the python interpreter when it returns from specific functions.

2) 我想暂停 python 解释器，将执行发送回在我的 C++ 程序中调用解释器的函数，最后将执行返回给 python 解释器，在它停止后的代码行上启动它.我想在执行属于 python 的时间之间维护全局变量和本地变量.

2) I would like to pause the python interpreter, send execution back to the function that called the interpreter in my C++ program, and finally return execution to the python interpreter, starting it on the line of code after where it stopped. I would like to maintain both globals and locals between the times where execution belongs to python.

第 1 部分我已经完成了.第 2 部分是我的问题.我不知道要保存什么以便我可以返回执行，或者根据保存的数据如何返回执行.

Part 1 I've finished. Part 2 is my question. I don't know what to save so I can return to execution, or how to return to execution given that saved data.

从我可以从 python API 文档中获得的信息来看，我将不得不保存执行帧的某些部分，但我什么也没找到.一些额外的问题...PyFrameObject 到底包含什么?令人惊讶的是，python API 文档从未解释过这一点.

From what I could get off the python API docs, I will have to save some part of the executing frame, but I haven't found anything. Some additional questions... What, exactly does a PyFrameObject contain? The python API docs, surprisingly, never explain that.

推荐答案

如果我理解你的问题，你就有一个调用 python 的 C++ 程序.当 python 完成一个函数的执行时，你想暂停解释器并从 C++ 代码停止的地方开始.一段时间后，您的 C++ 程序需要重新调用 python，并让 python 解释器从停止的地方开始.

If I understand your problem, you have a C++ program that calls into python. When python finishes executing a function, you want to pause the interpreter and pick up where the C++ code left off. Some time later your C++ program needs to cal back into python, and have the python interpreter pick up where it left off.

我不认为您可以通过一个线程轻松完成此操作.在暂停解释器之前，堆栈看起来像这样:

I don't think you can do this very easily with one thread. Before you pause the interpreter the stack looks like this:

[ top of stack ]
[ some interpreter frames ]
[ some c++ frames ] 

要暂停解释器，您需要保存解释器框架，并跳回到最顶层的 C++ 框架.然后要取消暂停，您需要恢复解释器帧，并将堆栈跳到您停止的位置.跳跃是可行的(参见 http://en.wikipedia.org/wiki/Setjmp.h)，但保存和恢复堆栈更难.我不知道有什么 API 可以做到这一点.

To pause the interpreter, you need to save off the interpreter frames, and jump back to the top-most C++ frame. Then to unpause, you need to restore the interpreter frames, and jump up the stack to where you left off. Jumping is doable (see http://en.wikipedia.org/wiki/Setjmp.h), but saving and restoring the stack is harder. I don't know of an API to do this.

但是你可以用两个线程来做到这一点.在 c++ 程序开始时创建的线程(称为线程 1)运行 c++ 代码，并创建线程 2 来运行 python 解释器.

However you could do this with two threads. The thread created at the start of your c++ program (call it thread 1) runs the c++ code, and it creates thread 2 to run the python interpreter.

最初(当运行 C++ 代码时)，线程 1 正在执行，线程 2 被阻塞(例如在条件变量上，请参阅 https://computing.llnl.gov/tutorials/pthreads/).当您运行或取消暂停解释器线程 1 信号条件变量，并等待它.这会唤醒线程 2(运行解释器)并导致线程 1 阻塞.当解释器需要暂停时，线程 2 向条件变量发出信号并等待它(因此线程 2 阻塞，线程 1 唤醒).您可以在线程之间来回弹跳以达到心满意足的程度.希望这会有所帮助.

Initially (when were running c++ code), thread 1 is executing and thread 2 is blocked (say on a condition variable, see https://computing.llnl.gov/tutorials/pthreads/). When you run or unpause the interpreter thread 1 signals the condition variable, and waits on it. This wakes up thread 2 (which runs the interpreter) and causes thread 1 to block. When the interpreter needs to pause, thread 2 signals the condition variable and waits on it (so thread 2 blocks, thread 1 wakes up). You can bounce back and forth between the threads to your heart's content. Hope this helps.

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