src/py-common/py-common.c

   1 /*
   2  * Copyright (c) 2019 EfficiOS Inc. and Linux Foundation
   3  * Copyright (c) 2019 Philippe Proulx <pproulx@efficios.com>
   4  * Copyright (c) 2019 Simon Marchi <simon.marchi@efficios.com>
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  19  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  22  * SOFTWARE.
  23  */
  24
  25 #define BT_LOG_OUTPUT_LEVEL log_level
  26 #define BT_LOG_TAG "PY-COMMON"
  27 #include "logging/log.h"
  28
  29 #include <Python.h>
  30
  31 #include "common/assert.h"
  32 #include "py-common.h"
  33
  34 BT_HIDDEN
  35 GString *bt_py_common_format_exception(int log_level)
  36 {
  37         PyObject *type = NULL;
  38         PyObject *value = NULL;
  39         PyObject *traceback = NULL;
  40         PyObject *traceback_module = NULL;
  41         PyObject *format_exception_func = NULL;
  42         PyObject *exc_str_list = NULL;
  43         GString *msg_buf = NULL;
  44         const char *format_exc_func_name;
  45         Py_ssize_t i;
  46
  47         BT_ASSERT(PyErr_Occurred());
  48         PyErr_Fetch(&type, &value, &traceback);
  49         BT_ASSERT(type);
  50
  51         /* Make sure `value` is what we expected: an instance of `type` */
  52         PyErr_NormalizeException(&type, &value, &traceback);
  53
  54         /*
  55          * Import the standard `traceback` module which contains the
  56          * functions to format an exception.
  57          */
  58         traceback_module = PyImport_ImportModule("traceback");
  59         if (!traceback_module) {
  60                 BT_LOGE_STR("Failed to import `traceback` module.");
  61                 goto error;
  62         }
  63
  64         /*
  65          * `traceback` can be `NULL`, when we fail to call a Python
  66          * function from native code (there is no Python stack at that
  67          * point). For example, a function which takes 5 positional
  68          * arguments, but 8 were given.
  69          */
  70         format_exc_func_name = traceback ? "format_exception" :
  71                 "format_exception_only";
  72         format_exception_func = PyObject_GetAttrString(traceback_module,
  73                 format_exc_func_name);
  74         if (!format_exception_func) {
  75                 BT_LOGE("Cannot find `%s` attribute in `traceback` module.",
  76                         format_exc_func_name);
  77                 goto error;
  78         }
  79
  80         if (!PyCallable_Check(format_exception_func)) {
  81                 BT_LOGE("`traceback.%s` attribute is not callable.",
  82                         format_exc_func_name);
  83                 goto error;
  84         }
  85
  86         exc_str_list = PyObject_CallFunctionObjArgs(format_exception_func,
  87                 type, value, traceback, NULL);
  88         if (!exc_str_list) {
  89                 if (BT_LOG_ON_ERROR) {
  90                         BT_LOGE("Failed to call `traceback.%s` function:",
  91                                 format_exc_func_name);
  92                         PyErr_Print();
  93                 }
  94
  95                 goto error;
  96         }
  97
  98         msg_buf = g_string_new(NULL);
  99
 100         for (i = 0; i < PyList_Size(exc_str_list); i++) {
 101                 PyObject *exc_str;
 102                 const char *str;
 103
 104                 exc_str = PyList_GetItem(exc_str_list, i);
 105                 BT_ASSERT(exc_str);
 106
 107                 /* `str` is owned by `exc_str`, not by us */
 108                 str = PyUnicode_AsUTF8(exc_str);
 109                 if (!str) {
 110                         if (BT_LOG_ON_ERROR) {
 111                                 BT_LOGE_STR("PyUnicode_AsUTF8() failed:");
 112                                 PyErr_Print();
 113                         }
 114
 115                         goto error;
 116                 }
 117
 118                 /* `str` has a trailing newline */
 119                 g_string_append(msg_buf, str);
 120         }
 121
 122         if (msg_buf->len > 0) {
 123                 /* Remove trailing newline if any */
 124                 if (msg_buf->str[msg_buf->len - 1] == '\n') {
 125                         g_string_truncate(msg_buf, msg_buf->len - 1);
 126                 }
 127         }
 128
 129         goto end;
 130
 131 error:
 132         if (msg_buf) {
 133                 g_string_free(msg_buf, TRUE);
 134                 msg_buf = NULL;
 135         }
 136
 137 end:
 138         Py_XDECREF(exc_str_list);
 139         Py_XDECREF(format_exception_func);
 140         Py_XDECREF(traceback_module);
 141
 142         /*
 143          * We can safely call PyErr_Restore() because we always call
 144          * PyErr_Fetch(), and having an error indicator is a function's
 145          * precondition.
 146          *
 147          * PyErr_Restore() steals our references.
 148          */
 149         PyErr_Restore(type, value, traceback);
 150
 151         return msg_buf;
 152 }