Turns on flag values for a data list. This function is used
to keep a small number of boolean flags in an object with
a data list without using any additional space. It is
not generally useful except in circumstances where space
is very tight. (It is used in the base
GObject type, for example.)
Available since: 2.8
Pointer to the location that holds a list.
The data is owned by the caller of the function.
The flags to turn on. The values of the flags are restricted by
G_DATALIST_FLAGS_MASK(currently 3; giving two possible boolean flags). A value for
flagsthat doesn’t fit within the mask is an error.