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GError

GError — error reporting.

Synopsis

enum                GConfError;
GError *            gconf_error_new                     (GConfError en,
                                                         const gchar *format,
                                                         ...);
GQuark              gconf_error_quark                   (void);
void                gconf_set_error                     (GError **err,
                                                         GConfError en,
                                                         const gchar *format,
                                                         ...);
GError *            gconf_compose_errors                (GError *err1,
                                                         GError *err2);

Description

The GError object is used to report errors that occur in GConf library routines. All functions that report errors work the same way:

  • The last argument to the function is a GError**, a pointer to a location where a GError* can be placed.

  • This last argument may be NULL, in which case no error will be returned.

  • If non-NULL, the argument should be the address of a GError* variable, which should be initialized to NULL.

  • If an error occurs, a GError will be allocated and placed in the return location; the caller must free the GError with g_error_free(). If no error occurs, the return location will be left untouched. That is, the test error != NULL should always be a reliable indicator of whether the operation failed.

It's also common that the return value of a function indicates whether or not an error occurred. Typically, TRUE is returned on success. In some cases, a NULL return value indicates failure. Either way, if the return value indicates failure and you passed a non-NULL value for the last argument to the function, a GError will be returned. If the return value indicates success, then a GError will never be returned. These relationships are guaranteed; that is, you can reliably use the return value to decide whether a GError was placed in the return location. If a function does not indicate success/failure by return value, you must check whether the GError is NULL to detect errors.

Here's a short error handling example:

  GError* err = NULL;
  if (!gconf_init(&err))
    {
      fprintf(stderr, _("Failed to init GConf: %s\n"), err->message);
      g_error_free(err);
      err = NULL;
    }

Details

enum GConfError

typedef enum {
  GCONF_ERROR_SUCCESS = 0,
  GCONF_ERROR_FAILED = 1,        /* Something didn't work, don't know why, probably unrecoverable
                                    so there's no point having a more specific errno */

  GCONF_ERROR_NO_SERVER = 2,     /* Server can't be launched/contacted */
  GCONF_ERROR_NO_PERMISSION = 3, /* don't have permission for that */
  GCONF_ERROR_BAD_ADDRESS = 4,   /* Address couldn't be resolved */
  GCONF_ERROR_BAD_KEY = 5,       /* directory or key isn't valid (contains bad
                                    characters, or malformed slash arrangement) */
  GCONF_ERROR_PARSE_ERROR = 6,   /* Syntax error when parsing */
  GCONF_ERROR_CORRUPT = 7,       /* Fatal error parsing/loading information inside the backend */
  GCONF_ERROR_TYPE_MISMATCH = 8, /* Type requested doesn't match type found */
  GCONF_ERROR_IS_DIR = 9,        /* Requested key operation on a dir */
  GCONF_ERROR_IS_KEY = 10,       /* Requested dir operation on a key */
  GCONF_ERROR_OVERRIDDEN = 11,   /* Read-only source at front of path has set the value */
  GCONF_ERROR_OAF_ERROR = 12,    /* liboaf error */
  GCONF_ERROR_LOCAL_ENGINE = 13, /* Tried to use remote operations on a local engine */
  GCONF_ERROR_LOCK_FAILED = 14,  /* Failed to get a lockfile */
  GCONF_ERROR_NO_WRITABLE_DATABASE = 15, /* nowhere to write a value */
  GCONF_ERROR_IN_SHUTDOWN = 16   /* server is shutting down */
} GConfError;

The GConfError enumeration allows client applications to differentiate between different kinds of error. You may wish to take specific actions depending on the error type.

GCONF_ERROR_SUCCESS

indicates that no error occurred, won't be returned in a GError.

GCONF_ERROR_FAILED

indicates failure, but no more specific GConfError applied.

GCONF_ERROR_NO_SERVER

indicates that the GConf server couldn't be contacted, probably a CORBA problem.

GCONF_ERROR_NO_PERMISSION

indicates that permission to access some resource was denied.

GCONF_ERROR_BAD_ADDRESS

indicates that a configuration source address was syntactically invalid or impossible to resolve.

GCONF_ERROR_BAD_KEY

indicates that a key was malformed.

GCONF_ERROR_PARSE_ERROR

indicates that some parsing was done (perhaps in a backend) and it failed.

GCONF_ERROR_CORRUPT

indicates that some part of the database is corrupt.

GCONF_ERROR_TYPE_MISMATCH

indicates that a specific type was required, and another type was found.

GCONF_ERROR_IS_DIR

indicates that an operation only applicable to keys was performed on a directory.

GCONF_ERROR_IS_KEY

indicates that an operation only applicable to directories was performed on a key.

GCONF_ERROR_OVERRIDDEN

indicates that the administrator has imposed a mandatory value, and it could not be changed.

GCONF_ERROR_OAF_ERROR

GCONF_ERROR_LOCAL_ENGINE

GCONF_ERROR_LOCK_FAILED

GCONF_ERROR_NO_WRITABLE_DATABASE

GCONF_ERROR_IN_SHUTDOWN


gconf_error_new ()

GError *            gconf_error_new                     (GConfError en,
                                                         const gchar *format,
                                                         ...);

Creates a new error. Normally the GConf library does this, but you might find a reason to do it as well. en is the error number, format is a printf()-style format for the error message, and the variable argument list is the same as in printf().

en :

the error number.

format :

printf()-style format for error description.

... :

arguments required by the format.

Returns :

newly-allocated GError.

gconf_error_quark ()

GQuark              gconf_error_quark                   (void);

Converts the string 'gconf-error-quark' to a GQuark and returns the value.

Returns :

the GQuark representing the string.

gconf_set_error ()

void                gconf_set_error                     (GError **err,
                                                         GConfError en,
                                                         const gchar *format,
                                                         ...);

Internal function.


gconf_compose_errors ()

GError *            gconf_compose_errors                (GError *err1,
                                                         GError *err2);

Internal function.

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