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(PyObject *py_exc_type,
  36                 PyObject *py_exc_value, PyObject *py_exc_tb,
  37                 int log_level, bool chain)
  38 {
  39         PyObject *traceback_module = NULL;
  40         PyObject *format_exception_func = NULL;
  41         PyObject *exc_str_list = NULL;
  42         GString *msg_buf = NULL;
  43         const char *format_exc_func_name;
  44         Py_ssize_t i;
  45
  46         /*
  47          * Import the standard `traceback` module which contains the
  48          * functions to format an exception.
  49          */
  50         traceback_module = PyImport_ImportModule("traceback");
  51         if (!traceback_module) {
  52                 BT_LOGE_STR("Failed to import `traceback` module.");
  53                 goto error;
  54         }
  55
  56         /*
  57          * `py_exc_tb` can be `NULL`, when we fail to call a Python
  58          * function from native code (there is no Python stack at that
  59          * point). For example, a function which takes 5 positional
  60          * arguments, but 8 were given.
  61          */
  62         format_exc_func_name = py_exc_tb ? "format_exception" :
  63                 "format_exception_only";
  64         format_exception_func = PyObject_GetAttrString(traceback_module,
  65                 format_exc_func_name);
  66         if (!format_exception_func) {
  67                 BT_LOGE("Cannot find `%s` attribute in `traceback` module.",
  68                         format_exc_func_name);
  69                 goto error;
  70         }
  71
  72         if (!PyCallable_Check(format_exception_func)) {
  73                 BT_LOGE("`traceback.%s` attribute is not callable.",
  74                         format_exc_func_name);
  75                 goto error;
  76         }
  77
  78         /*
  79          * If we are calling format_exception_only, `py_exc_tb` is NULL, so the
  80          * effective argument list is of length 2.
  81          */
  82         exc_str_list = PyObject_CallFunctionObjArgs(format_exception_func,
  83                 py_exc_type, py_exc_value, py_exc_tb, Py_None /* limit */,
  84                 chain ? Py_True : Py_False /* chain */, NULL);
  85         if (!exc_str_list) {
  86                 if (BT_LOG_ON_ERROR) {
  87                         BT_LOGE("Failed to call `traceback.%s` function:",
  88                                 format_exc_func_name);
  89                         PyErr_Print();
  90                 }
  91
  92                 goto error;
  93         }
  94
  95         msg_buf = g_string_new(NULL);
  96
  97         for (i = 0; i < PyList_Size(exc_str_list); i++) {
  98                 PyObject *exc_str;
  99                 const char *str;
 100
 101                 exc_str = PyList_GetItem(exc_str_list, i);
 102                 BT_ASSERT(exc_str);
 103
 104                 /* `str` is owned by `exc_str`, not by us */
 105                 str = PyUnicode_AsUTF8(exc_str);
 106                 if (!str) {
 107                         if (BT_LOG_ON_ERROR) {
 108                                 BT_LOGE_STR("PyUnicode_AsUTF8() failed:");
 109                                 PyErr_Print();
 110                         }
 111
 112                         goto error;
 113                 }
 114
 115                 /* `str` has a trailing newline */
 116                 g_string_append(msg_buf, str);
 117         }
 118
 119         if (msg_buf->len > 0) {
 120                 /* Remove trailing newline if any */
 121                 if (msg_buf->str[msg_buf->len - 1] == '\n') {
 122                         g_string_truncate(msg_buf, msg_buf->len - 1);
 123                 }
 124         }
 125
 126         goto end;
 127
 128 error:
 129         if (msg_buf) {
 130                 g_string_free(msg_buf, TRUE);
 131                 msg_buf = NULL;
 132         }
 133
 134 end:
 135         Py_XDECREF(exc_str_list);
 136         Py_XDECREF(format_exception_func);
 137         Py_XDECREF(traceback_module);
 138
 139         return msg_buf;
 140 }
 141
 142 BT_HIDDEN
 143 GString *bt_py_common_format_current_exception(int log_level)
 144 {
 145         GString *result;
 146         PyObject *py_exc_type = NULL;
 147         PyObject *py_exc_value = NULL;
 148         PyObject *py_exc_tb = NULL;
 149
 150         BT_ASSERT(PyErr_Occurred());
 151         PyErr_Fetch(&py_exc_type, &py_exc_value, &py_exc_tb);
 152         BT_ASSERT(py_exc_type);
 153
 154         /*
 155          * Make sure `py_exc_value` is what we expected: an instance of
 156          * `py_exc_type`.
 157          */
 158         PyErr_NormalizeException(&py_exc_type, &py_exc_value, &py_exc_tb);
 159
 160         result = bt_py_common_format_exception(py_exc_type, py_exc_value,
 161                 py_exc_tb, log_level, true);
 162
 163         /*
 164          * We can safely call PyErr_Restore() because we always call
 165          * PyErr_Fetch(), and having an error indicator is a function's
 166          * precondition.
 167          *
 168          * PyErr_Restore() steals our references.
 169          */
 170         PyErr_Restore(py_exc_type, py_exc_value, py_exc_tb);
 171
 172         return result;
 173 }