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