Provided by: libx11-doc_1.6.2-1ubuntu2_all
XFree - free client data
int XFree(void *data);
data Specifies the data that are to be freed.
The XFree function is a general-purpose Xlib routine that frees the specified data. You must use it to free any objects that were allocated by Xlib, unless an alternate function is explicitly specified for the object. A NULL pointer cannot be passed to this function.
Xlib - C Language X Interface