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6
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1 /* Error handling -- see also run.c */
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2
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3 /* New error handling interface.
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4
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5 The following problem exists (existed): methods of built-in modules
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6 are called with 'self' and 'args' arguments, but without a context
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7 argument, so they have no way to raise a specific exception.
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8 The same is true for the object implementations: no context argument.
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9 The old convention was to set 'errno' and to return NULL.
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10 The caller (usually call_function() in eval.c) detects the NULL
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11 return value and then calls puterrno(ctx) to turn the errno value
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12 into a true exception. Problems with this approach are:
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13 - it used standard errno values to indicate Python-specific errors,
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14 but this means that when such an error code is reported by UNIX the
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15 user gets a confusing message
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16 - errno is a global variable, which makes extensions to a multi-
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17 threading environment difficult; e.g., in IRIX, multi-threaded
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18 programs must use the function getoserror() (sp.?) instead of
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19 looking in errno
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20 - there is no portable way to add new error numbers for specic
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21 situations -- the value space for errno is reserved to the OS, yet
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22 the way to turn module-specific errors into a module-specific
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23 exception requires module-specific values for errno
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24 - there is no way to add a more situation-specific message to an
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25 error.
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26
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27 The new interface solves all these problems. To return an error, a
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28 built-in function calls err_set(exception), err_set(valexception,
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29 value) or err_setstr(exception, string), and returns NULL. These
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30 functions save the value for later use by puterrno(). To adapt this
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31 scheme to a multi-threaded environment, only the implementation of
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32 err_setval() has to be changed.
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33 */
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34
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35 #include <stdio.h>
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36
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37 #include "PROTO.h"
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38 #include "object.h"
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39 #include "stringobject.h"
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40 #include "errors.h"
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41
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42 /* Last exception stored by err_setval() */
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43
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44 static object *last_exception;
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45 static object *last_exc_val;
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46
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47 void
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48 err_setval(exception, value)
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49 object *exception;
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50 object *value;
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51 {
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52 if (last_exception != NULL)
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53 DECREF(last_exception);
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54 if (exception != NULL)
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55 INCREF(exception);
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56 last_exception = exception;
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57
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58 if (last_exc_val != NULL)
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59 DECREF(last_exc_val);
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60 if (value != NULL)
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61 INCREF(value);
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62 last_exc_val = value;
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63 }
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64
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65 void
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66 err_set(exception)
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67 object *exception;
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68 {
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69 err_setval(exception, (object *)NULL);
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70 }
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71
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72 void
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73 err_setstr(exception, string)
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74 object *exception;
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75 char *string;
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76 {
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77 object *value = newstringobject(string);
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78 err_setval(exception, value);
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79 if (value != NULL)
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80 DECREF(value);
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81 }
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82
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83 int
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84 err_occurred()
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85 {
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86 return last_exception != NULL;
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87 }
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88
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89 void
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90 err_get(p_exc, p_val)
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91 object **p_exc;
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92 object **p_val;
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93 {
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94 *p_exc = last_exception;
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95 last_exception = NULL;
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96 *p_val = last_exc_val;
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97 last_exc_val = NULL;
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98 }
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99
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100 void
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101 err_clear()
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102 {
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103 if (last_exception != NULL) {
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104 DECREF(last_exception);
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105 last_exception = NULL;
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106 }
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107 if (last_exc_val != NULL) {
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108 DECREF(last_exc_val);
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109 last_exc_val = NULL;
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110 }
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111 }
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