plugins/python/errors.c

   1 /* nbdkit
   2  * Copyright Red Hat
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *
  11  * * Redistributions in binary form must reproduce the above copyright
  12  * notice, this list of conditions and the following disclaimer in the
  13  * documentation and/or other materials provided with the distribution.
  14  *
  15  * * Neither the name of Red Hat nor the names of its contributors may be
  16  * used to endorse or promote products derived from this software without
  17  * specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  22  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  26  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  27  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  29  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <config.h>
  34
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37
  38 #include "cleanup.h"
  39
  40 #include "plugin.h"
  41
  42 /* This is the fallback in case we cannot get the full traceback. */
  43 static void
  44 print_python_error (const char *callback, PyObject *error)
  45 {
  46   PyObject *error_str;
  47   CLEANUP_FREE char *error_cstr = NULL;
  48
  49   error_str = PyObject_Str (error);
  50   error_cstr = python_to_string (error_str);
  51   nbdkit_error ("%s: %s: error: %s",
  52                 script, callback,
  53                 error_cstr ? error_cstr : "<unknown>");
  54   Py_DECREF (error_str);
  55 }
  56
  57 /* Convert the Python traceback to a string and call nbdkit_error.
  58  * https://stackoverflow.com/a/15907460/7126113
  59  */
  60 static int
  61 print_python_traceback (const char *callback,
  62                         PyObject *type, PyObject *error, PyObject *traceback)
  63 {
  64   PyObject *module_name, *traceback_module, *format_exception_fn, *rv,
  65     *traceback_str;
  66   CLEANUP_FREE char *traceback_cstr = NULL;
  67
  68   module_name = PyUnicode_FromString ("traceback");
  69   traceback_module = PyImport_Import (module_name);
  70   Py_DECREF (module_name);
  71
  72   /* couldn't 'import traceback' */
  73   if (traceback_module == NULL)
  74     return -1;
  75
  76   format_exception_fn = PyObject_GetAttrString (traceback_module,
  77                                                 "format_exception");
  78   if (format_exception_fn == NULL)
  79     return -1;
  80   if (!PyCallable_Check (format_exception_fn))
  81     return -1;
  82
  83   rv = PyObject_CallFunctionObjArgs (format_exception_fn,
  84                                      type, error, traceback, NULL);
  85   if (rv == NULL)
  86     return -1;
  87   traceback_str = PyUnicode_Join (NULL, rv);
  88   Py_DECREF (rv);
  89   traceback_cstr = python_to_string (traceback_str);
  90   if (traceback_cstr == NULL) {
  91     Py_DECREF (traceback_str);
  92     return -1;
  93   }
  94
  95   nbdkit_error ("%s: %s: error: %s",
  96                 script, callback,
  97                 traceback_cstr);
  98   Py_DECREF (traceback_str);
  99
 100   /* This means we succeeded in calling nbdkit_error. */
 101   return 0;
 102 }
 103
 104 int
 105 check_python_failure (const char *callback)
 106 {
 107   if (PyErr_Occurred ()) {
 108     PyObject *type, *error, *traceback;
 109
 110     PyErr_Fetch (&type, &error, &traceback);
 111     PyErr_NormalizeException (&type, &error, &traceback);
 112
 113     /* Try to print the full traceback. */
 114     if (print_python_traceback (callback, type, error, traceback) == -1) {
 115       /* Couldn't do that, so fall back to converting the Python error
 116        * to a string.
 117        */
 118       print_python_error (callback, error);
 119     }
 120
 121     /* In all cases this returns -1 to indicate that a Python error
 122      * occurred.
 123      */
 124     return -1;
 125   }
 126   return 0;
 127 }