Move to kernel style SPDX license identifiers

[babeltrace.git] / src / py-common / py-common.c

/*
 * SPDX-License-Identifier: MIT
 *
 * Copyright (c) 2019 EfficiOS Inc. and Linux Foundation
 * Copyright (c) 2019 Philippe Proulx <pproulx@efficios.com>
 * Copyright (c) 2019 Simon Marchi <simon.marchi@efficios.com>
 */

#define BT_LOG_OUTPUT_LEVEL log_level
#define BT_LOG_TAG "PY-COMMON"
#include "logging/log.h"

#include <stdbool.h>

#include <Python.h>

#include "common/assert.h"
#include "py-common.h"

/*
 * Concatenate strings in list `py_str_list`, returning the result as a
 * GString.  Remove the trailing \n, if the last string ends with a \n.
 */
static
GString *py_str_list_to_gstring(PyObject *py_str_list, int log_level)
{
	Py_ssize_t i;
	GString *gstr;

	gstr = g_string_new(NULL);
	if (!gstr) {
		BT_LOGE("Failed to allocate a GString.");
		goto end;
	}

	for (i = 0; i < PyList_Size(py_str_list); i++) {
		PyObject *py_str;
		const char *str;

		py_str = PyList_GetItem(py_str_list, i);
		BT_ASSERT(py_str);
		BT_ASSERT(PyUnicode_CheckExact(py_str));

		/* `str` is owned by `py_str`, not by us */
		str = PyUnicode_AsUTF8(py_str);
		if (!str) {
			if (BT_LOG_ON_ERROR) {
				BT_LOGE_STR("PyUnicode_AsUTF8() failed:");
				PyErr_Print();
			}

			goto error;
		}

		/* `str` has a trailing newline */
		g_string_append(gstr, str);
	}

	if (gstr->len > 0) {
		/* Remove trailing newline if any */
		if (gstr->str[gstr->len - 1] == '\n') {
			g_string_truncate(gstr, gstr->len - 1);
		}
	}

	goto end;

error:
	g_string_free(gstr, TRUE);
	gstr = NULL;

end:
	return gstr;
}

BT_HIDDEN
GString *bt_py_common_format_tb(PyObject *py_exc_tb, int log_level)
{
	PyObject *traceback_module = NULL;
	PyObject *format_tb_func = NULL;
	PyObject *exc_str_list = NULL;
	GString *msg_buf = NULL;

	BT_ASSERT(py_exc_tb);

	/*
	 * Import the standard `traceback` module which contains the
	 * functions to format a traceback.
	 */
	traceback_module = PyImport_ImportModule("traceback");
	if (!traceback_module) {
		BT_LOGE_STR("Failed to import `traceback` module.");
		goto error;
	}

	format_tb_func = PyObject_GetAttrString(traceback_module,
		"format_tb");
	if (!format_tb_func) {
		BT_LOGE("Cannot find `format_tb` attribute in `traceback` module.");
		goto error;
	}

	if (!PyCallable_Check(format_tb_func)) {
		BT_LOGE("`traceback.format_tb` attribute is not callable.");
		goto error;
	}

	/*
	 * If we are calling format_exception_only, `py_exc_tb` is NULL, so the
	 * effective argument list is of length 2.
	 */
	exc_str_list = PyObject_CallFunctionObjArgs(
		format_tb_func, py_exc_tb, NULL);
	if (!exc_str_list) {
		if (BT_LOG_ON_ERROR) {
			BT_LOGE("Failed to call `traceback.format_tb` function:");
			PyErr_Print();
		}

		goto error;
	}

	msg_buf = py_str_list_to_gstring(exc_str_list, log_level);
	if (!msg_buf) {
		goto error;
	}

error:
	Py_XDECREF(traceback_module);
	Py_XDECREF(format_tb_func);
	Py_XDECREF(exc_str_list);

	return msg_buf;
}

BT_HIDDEN
GString *bt_py_common_format_exception(PyObject *py_exc_type,
		PyObject *py_exc_value, PyObject *py_exc_tb,
		int log_level, bool chain)
{
	PyObject *traceback_module = NULL;
	PyObject *format_exception_func = NULL;
	PyObject *exc_str_list = NULL;
	GString *msg_buf = NULL;
	const char *format_exc_func_name;

	/*
	 * Import the standard `traceback` module which contains the
	 * functions to format an exception.
	 */
	traceback_module = PyImport_ImportModule("traceback");
	if (!traceback_module) {
		BT_LOGE_STR("Failed to import `traceback` module.");
		goto error;
	}

	/*
	 * `py_exc_tb` can be `NULL`, when we fail to call a Python
	 * function from native code (there is no Python stack at that
	 * point). For example, a function which takes 5 positional
	 * arguments, but 8 were given.
	 */
	format_exc_func_name = py_exc_tb ? "format_exception" :
		"format_exception_only";
	format_exception_func = PyObject_GetAttrString(traceback_module,
		format_exc_func_name);
	if (!format_exception_func) {
		BT_LOGE("Cannot find `%s` attribute in `traceback` module.",
			format_exc_func_name);
		goto error;
	}

	if (!PyCallable_Check(format_exception_func)) {
		BT_LOGE("`traceback.%s` attribute is not callable.",
			format_exc_func_name);
		goto error;
	}

	/*
	 * If we are calling format_exception_only, `py_exc_tb` is NULL, so the
	 * effective argument list is of length 2.
	 */
	exc_str_list = PyObject_CallFunctionObjArgs(format_exception_func,
		py_exc_type, py_exc_value, py_exc_tb, Py_None /* limit */,
		chain ? Py_True : Py_False /* chain */, NULL);
	if (!exc_str_list) {
		if (BT_LOG_ON_ERROR) {
			BT_LOGE("Failed to call `traceback.%s` function:",
				format_exc_func_name);
			PyErr_Print();
		}

		goto error;
	}

	msg_buf = py_str_list_to_gstring(exc_str_list, log_level);
	if (!msg_buf) {
		goto error;
	}

error:
	Py_XDECREF(exc_str_list);
	Py_XDECREF(format_exception_func);
	Py_XDECREF(traceback_module);

	return msg_buf;
}

BT_HIDDEN
GString *bt_py_common_format_current_exception(int log_level)
{
	GString *result;
	PyObject *py_exc_type = NULL;
	PyObject *py_exc_value = NULL;
	PyObject *py_exc_tb = NULL;

	BT_ASSERT(PyErr_Occurred());
	PyErr_Fetch(&py_exc_type, &py_exc_value, &py_exc_tb);
	BT_ASSERT(py_exc_type);

	/*
	 * Make sure `py_exc_value` is what we expected: an instance of
	 * `py_exc_type`.
	 */
	PyErr_NormalizeException(&py_exc_type, &py_exc_value, &py_exc_tb);

	result = bt_py_common_format_exception(py_exc_type, py_exc_value,
		py_exc_tb, log_level, true);

	/*
	 * We can safely call PyErr_Restore() because we always call
	 * PyErr_Fetch(), and having an error indicator is a function's
	 * precondition.
	 *
	 * PyErr_Restore() steals our references.
	 */
	PyErr_Restore(py_exc_type, py_exc_value, py_exc_tb);

	return result;
}