Volume 7A: XView Programming Manual

NULL);

break;

/* ... */

}

As you can see, unless you are implementing the internals of an XView package,

xv_error() may be of limited use. However, this example demonstrates how

xv_error() can be called internally by XView.

24.4.1.1 Error severity

In the above example, the reason to call xv_error() is not a serious one, at least not one

that should terminate the program. By default, calling xv_error() is a recoverable error,

so in order to specify a non-recoverable error, the call to xv_error() should pass the attri-

bute, ERROR_SEVERITY, and the value ERROR_NON_RECOVERABLE. Unrecoverable errors

generally terminate using exit() with a non-zero exit status. However, abort() may be

used instead to generate a core image used for debugging.

In any event, if the error handler is called, it should print a warning message and either con-

tinue or exit accordingly. If you install your own error routine, the choice is yours. Example

24-1 in the next section, shows how the error severity can be evaluated and acted upon

accordingly.

24.4.2 Revisiting the Error Handler

Advanced usage of the ERROR package provides us with the ability to scan the attribute list in

search of the causes of the error. With this information, you can print out more useful error

messages or display them in a manner other than printing to stderr.

Recall that there are two parameters passed to the function:

error_proc(object, avlist)

Xv_object object;

Attr_avlist avlist;

object is the object in which the xv_* call failed to operate. You