# Profiling and tracing

Python インタプリタは、プロファイル: 分析 (profile) や実行のトレース: 追跡 (trace) といった機能を組み込むために低水準のサポートを提供しています。このサポートは、プロファイルやデバッグ、適用範囲分析 (coverage analysis) ツールなどに使われます。

この C インターフェースは、プロファイルやトレース作業時に、Python レベルの呼び出し可能オブジェクトが呼び出されることによるオーバヘッドを避け、直接 C 関数呼び出しが行えるようにしています。プロファイルやトレース機能の本質的な特性は変わっていません; インターフェースではトレース関数をスレッドごとにインストールでき、トレース関数に報告される基本イベント (basic event) は以前のバージョンにおいて Python レベルのトレース関数で報告されていたものと同じです。

typedef int (*Py_tracefunc)(PyObject *obj, PyFrameObject *frame, int what, PyObject *arg)

  The type of the trace function registered using `PyEval_SetProfile()` and `PyEval_SetTrace()`. The first parameter is the object passed to the registration function as obj, frame is the frame object to which the event pertains, what is one of the constants `PyTrace_CALL`, `PyTrace_EXCEPTION`, `PyTrace_LINE`, `PyTrace_RETURN`, `PyTrace_C_CALL`, `PyTrace_C_EXCEPTION`, `PyTrace_C_RETURN`, or `PyTrace_OPCODE`, and arg depends on the value of what:

  what の値 | arg の意味
  --- | ---
  `PyTrace_CALL` | 常に `Py_None` 。
  `PyTrace_EXCEPTION` | `sys.exc_info()` の返す例外情報です。
  `PyTrace_LINE` | 常に `Py_None` 。
  `PyTrace_RETURN` | 呼び出し側に返される予定の値か、例外によって関数を抜ける場合は `NULL` です。
  `PyTrace_C_CALL` | 呼び出される関数オブジェクト。
  `PyTrace_C_EXCEPTION` | 呼び出される関数オブジェクト。
  `PyTrace_C_RETURN` | 呼び出される関数オブジェクト。
  `PyTrace_OPCODE` | 常に `Py_None` 。

int PyTrace_CALL

  関数やメソッドが新たに呼び出されたり、ジェネレータが新たなエントリの処理に入ったことを報告する際の、 `Py_tracefunc` の what の値です。イテレータやジェネレータ関数の生成は、対応するフレーム内の Python バイトコードに制御の委譲 (control transfer) が起こらないため報告されないので注意してください。

int PyTrace_EXCEPTION

  The value of the what parameter to a `Py_tracefunc` function when an exception has been raised. The callback function is called with this value for what when after any bytecode is processed after which the exception becomes set within the frame being executed. The effect of this is that as exception propagation causes the Python stack to unwind, the callback is called upon return to each frame as the exception propagates. Only trace functions receive these events; they are not needed by the profiler.

int PyTrace_LINE

  The value passed as the what parameter to a `Py_tracefunc` function (but not a profiling function) when a line-number event is being reported. It may be disabled for a frame by setting `f_trace_lines` to 0 on that frame.

int PyTrace_RETURN

  呼び出しが返るときに `Py_tracefunc` 関数に what 引数として渡す値です。

int PyTrace_C_CALL

  C関数を呼び出す直前に `Py_tracefunc` 関数の what 引数として渡す値です。

int PyTrace_C_EXCEPTION

  C関数が例外を送出したときに `Py_tracefunc` 関数の what 引数として渡す値です。

int PyTrace_C_RETURN

  C関数から戻るときに `Py_tracefunc` 関数の what 引数として渡す値です。

int PyTrace_OPCODE

  The value for the what parameter to `Py_tracefunc` functions (but not profiling functions) when a new opcode is about to be executed. This event is not emitted by default: it must be explicitly requested by setting `f_trace_opcodes` to 1 on the frame.

void PyEval_SetProfile(Py_tracefunc func, PyObject *obj)

  Set the profiler function to func. The obj parameter is passed to the function as its first parameter, and may be any Python object, or `NULL`. If the profile function needs to maintain state, using a different value for obj for each thread provides a convenient and thread-safe place to store it. The profile function is called for all monitored events except `PyTrace_LINE` `PyTrace_OPCODE` and `PyTrace_EXCEPTION`.

  `sys.setprofile()` 関数も参照してください。

  The caller must have an attached thread state.

void PyEval_SetProfileAllThreads(Py_tracefunc func, PyObject *obj)

  Like `PyEval_SetProfile()` but sets the profile function in all running threads belonging to the current interpreter instead of the setting it only on the current thread.

  The caller must have an attached thread state.

  As `PyEval_SetProfile()`, this function ignores any exceptions raised while setting the profile functions in all threads.

Added in version 3.12.

void PyEval_SetTrace(Py_tracefunc func, PyObject *obj)

  Set the tracing function to func. This is similar to `PyEval_SetProfile()`, except the tracing function does receive line-number events and per-opcode events, but does not receive any event related to C function objects being called. Any trace function registered using `PyEval_SetTrace()` will not receive `PyTrace_C_CALL`, `PyTrace_C_EXCEPTION` or `PyTrace_C_RETURN` as a value for the what parameter.

  `sys.settrace()` 関数も参照してください。

  The caller must have an attached thread state.

void PyEval_SetTraceAllThreads(Py_tracefunc func, PyObject *obj)

  Like `PyEval_SetTrace()` but sets the tracing function in all running threads belonging to the current interpreter instead of the setting it only on the current thread.

  The caller must have an attached thread state.

  As `PyEval_SetTrace()`, this function ignores any exceptions raised while setting the trace functions in all threads.

Added in version 3.12.

# Reference tracing

Added in version 3.13.

typedef int (*PyRefTracer)(PyObject*, int event, void *data)

  The type of the trace function registered using `PyRefTracer_SetTracer()`. The first parameter is a Python object that has been just created (when event is set to `PyRefTracer_CREATE`) or about to be destroyed (when event is set to `PyRefTracer_DESTROY`). The data argument is the opaque pointer that was provided when `PyRefTracer_SetTracer()` was called.

  If a new tracing function is registered replacing the current one, a call to the trace function will be made with the object set to NULL and event set to `PyRefTracer_TRACKER_REMOVED`. This will happen just before the new function is registered.

Added in version 3.13.

int PyRefTracer_CREATE

  The value for the event parameter to `PyRefTracer` functions when a Python object has been created.

int PyRefTracer_DESTROY

  The value for the event parameter to `PyRefTracer` functions when a Python object has been destroyed.

int PyRefTracer_TRACKER_REMOVED

  The value for the event parameter to `PyRefTracer` functions when the current tracer is about to be replaced by a new one.

  Added in version 3.14.

int PyRefTracer_SetTracer(PyRefTracer tracer, void *data)

  Register a reference tracer function. The function will be called when a new Python object has been created or when an object is going to be destroyed. If data is provided it must be an opaque pointer that will be provided when the tracer function is called. Return `0` on success. Set an exception and return `-1` on error.

  Note that tracer functions must not create Python objects inside or otherwise the call will be re-entrant. The tracer also must not clear any existing exception or set an exception. A thread state will be active every time the tracer function is called.

  There must be an attached thread state when calling this function.

  If another tracer function was already registered, the old function will be called with event set to `PyRefTracer_TRACKER_REMOVED` just before the new function is registered.

Added in version 3.13.

PyRefTracer PyRefTracer_GetTracer(void **data)

  Get the registered reference tracer function and the value of the opaque data pointer that was registered when `PyRefTracer_SetTracer()` was called. If no tracer was registered this function will return NULL and will set the data pointer to NULL.

  There must be an attached thread state when calling this function.

Added in version 3.13.