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.