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143 lines
3.4 KiB
C
143 lines
3.4 KiB
C
/* Error handling -- see also run.c */
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/* New error handling interface.
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The following problem exists (existed): methods of built-in modules
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are called with 'self' and 'args' arguments, but without a context
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argument, so they have no way to raise a specific exception.
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The same is true for the object implementations: no context argument.
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The old convention was to set 'errno' and to return NULL.
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The caller (usually call_function() in eval.c) detects the NULL
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return value and then calls puterrno(ctx) to turn the errno value
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into a true exception. Problems with this approach are:
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- it used standard errno values to indicate Python-specific errors,
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but this means that when such an error code is reported by UNIX the
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user gets a confusing message
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- errno is a global variable, which makes extensions to a multi-
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threading environment difficult; e.g., in IRIX, multi-threaded
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programs must use the function getoserror() (sp.?) instead of
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looking in errno
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- there is no portable way to add new error numbers for specic
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situations -- the value space for errno is reserved to the OS, yet
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the way to turn module-specific errors into a module-specific
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exception requires module-specific values for errno
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- there is no way to add a more situation-specific message to an
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error.
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The new interface solves all these problems. To return an error, a
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built-in function calls err_set(exception), err_set(valexception,
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value) or err_setstr(exception, string), and returns NULL. These
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functions save the value for later use by puterrno(). To adapt this
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scheme to a multi-threaded environment, only the implementation of
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err_setval() has to be changed.
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*/
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#include <stdio.h>
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#include "PROTO.h"
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#include "object.h"
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#include "stringobject.h"
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#include "errors.h"
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/* Last exception stored by err_setval() */
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static object *last_exception;
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static object *last_exc_val;
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void
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err_setval(exception, value)
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object *exception;
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object *value;
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{
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if (last_exception != NULL)
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DECREF(last_exception);
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if (exception != NULL)
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INCREF(exception);
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last_exception = exception;
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if (last_exc_val != NULL)
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DECREF(last_exc_val);
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if (value != NULL)
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INCREF(value);
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last_exc_val = value;
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}
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void
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err_set(exception)
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object *exception;
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{
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err_setval(exception, (object *)NULL);
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}
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void
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err_setstr(exception, string)
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object *exception;
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char *string;
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{
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object *value = newstringobject(string);
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err_setval(exception, value);
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if (value != NULL)
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DECREF(value);
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}
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int
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err_occurred()
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{
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return last_exception != NULL;
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}
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void
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err_get(p_exc, p_val)
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object **p_exc;
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object **p_val;
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{
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*p_exc = last_exception;
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last_exception = NULL;
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*p_val = last_exc_val;
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last_exc_val = NULL;
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}
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void
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err_clear()
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{
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if (last_exception != NULL) {
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DECREF(last_exception);
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last_exception = NULL;
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}
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if (last_exc_val != NULL) {
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DECREF(last_exc_val);
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last_exc_val = NULL;
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}
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}
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/* Convenience functions to set a type error exception and return 0 */
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int
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err_badarg()
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{
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err_setstr(TypeError, "illegal argument type for built-in function");
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return 0;
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}
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object *
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err_nomem()
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{
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err_setstr(MemoryError, "in built-in function");
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return NULL;
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}
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object *
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err_errno(exc)
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object *exc;
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{
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object *v = newtupleobject(2);
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if (v != NULL) {
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settupleitem(v, 0, newintobject((long)errno));
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settupleitem(v, 1, newstringobject(strerror(errno)));
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}
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err_setval(exc, v);
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if (v != NULL)
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DECREF(v);
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return NULL;
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}
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