annotate Python/errors.c @ 66:46cb14aec10a legacy-trunk

Reformulated err_badarg error message.
author Guido van Rossum <guido@python.org>
date Fri, 09 Nov 1990 15:05:53 +0000
parents 433f52d1d958
children a6934380c6e7
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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"
37
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39 #include "intobject.h"
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40 #include "stringobject.h"
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41 #include "tupleobject.h"
6
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42 #include "errors.h"
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43
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44 extern char *strerror PROTO((int));
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45
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46 /* Last exception stored by err_setval() */
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47
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48 static object *last_exception;
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49 static object *last_exc_val;
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50
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51 void
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52 err_setval(exception, value)
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53 object *exception;
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54 object *value;
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55 {
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56 if (last_exception != NULL)
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57 DECREF(last_exception);
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58 if (exception != NULL)
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59 INCREF(exception);
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60 last_exception = exception;
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61
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62 if (last_exc_val != NULL)
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63 DECREF(last_exc_val);
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64 if (value != NULL)
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65 INCREF(value);
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66 last_exc_val = value;
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67 }
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68
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69 void
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70 err_set(exception)
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71 object *exception;
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72 {
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73 err_setval(exception, (object *)NULL);
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74 }
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75
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76 void
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77 err_setstr(exception, string)
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78 object *exception;
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79 char *string;
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80 {
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81 object *value = newstringobject(string);
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82 err_setval(exception, value);
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83 if (value != NULL)
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84 DECREF(value);
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85 }
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86
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87 int
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88 err_occurred()
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89 {
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90 return last_exception != NULL;
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91 }
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92
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93 void
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94 err_get(p_exc, p_val)
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95 object **p_exc;
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96 object **p_val;
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97 {
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98 *p_exc = last_exception;
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99 last_exception = NULL;
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100 *p_val = last_exc_val;
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101 last_exc_val = NULL;
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102 }
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103
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104 void
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105 err_clear()
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106 {
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107 if (last_exception != NULL) {
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108 DECREF(last_exception);
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109 last_exception = NULL;
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110 }
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111 if (last_exc_val != NULL) {
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112 DECREF(last_exc_val);
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113 last_exc_val = NULL;
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114 }
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115 }
9
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116
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117 /* Convenience functions to set a type error exception and return 0 */
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118
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119 int
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120 err_badarg()
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121 {
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122 err_setstr(TypeError, "illegal argument type for built-in operation");
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123 return 0;
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124 }
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125
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126 object *
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127 err_nomem()
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128 {
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129 err_setstr(MemoryError, "in built-in function");
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130 return NULL;
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131 }
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132
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133 object *
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134 err_errno(exc)
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135 object *exc;
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136 {
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137 object *v = newtupleobject(2);
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138 if (v != NULL) {
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139 settupleitem(v, 0, newintobject((long)errno));
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140 settupleitem(v, 1, newstringobject(strerror(errno)));
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141 }
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142 err_setval(exc, v);
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143 if (v != NULL)
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144 DECREF(v);
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145 return NULL;
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146 }
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147
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148 void
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149 err_badcall()
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150 {
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151 err_setstr(SystemError, "bad argument to internal function");
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152 }