GLibprefix_error

void
g_prefix_error (
  GError** err,
  const gchar* format,
  ...
)

Formats a string according to format and prefix it to an existing error message. If err is NULL (ie: no error variable) then do nothing.

If *err is NULL (ie: an error variable is present but there is no error condition) then also do nothing.

Available since:	2.16
This function is not directly available to language bindings

`err`	`GError`
	A return location for a `GError`.
	The argument will be modified by the function.
	The argument can be set to `NULL`.
	The argument can be `NULL`.
	The called function takes ownership of the data, and is responsible for freeing it.
`format`	`const gchar*`
	Printf()-style format string.
	The data is owned by the caller of the function.
	The value is a NUL terminated UTF-8 string.
`...`
	Arguments to `format`.