GError
is the standard error reporting mechanism for GLib-using code, and can be
thought of as a C implementation of an
exception.
Any kind of runtime failure (anything which is not a
programmer error) must be handled by
including a GError**
parameter in the function, and setting a
useful and relevant GError describing the failure, before returning from
the function. Programmer errors must not be handled using GError: use
assertions, pre-conditions or post-conditions instead.
GError should be used in preference to a simple return code, as it can convey more information, and is also supported by all GLib tools. For example, introspecting an API will automatically detect all GError parameters so that they can be converted to exceptions in other languages.
Printing warnings to the console must not be done in library code: use a GError, and the calling code can propagate it further upwards, decide to handle it, or decide to print it to the console. Ideally, the only code which prints to the console will be top-level application code, and not library code.
Any function call which can take a GError**
, should
take such a parameter, and the returned GError should be handled
appropriately. There are very few situations where ignoring a potential
error by passing NULL
to a GError**
parameter is
acceptable.
The GLib API documentation contains a full tutorial for using GError.