The attribute Unchecked_Access is used to create
access values in an unsafe manner — the programmer is responsible
for preventing “dangling references”.
All rules and semantics that
apply to X'Access (see
3.10.2) apply also
to X'Unchecked_Access, except that, for the purposes of accessibility
rules and checks, it is as if X were declared immediately within a library
package.
NOTE 1 This attribute is provided
to support the situation where a local object is to be inserted into
a global linked data structure, when the programmer knows that it will
always be removed from the data structure prior to exiting the object's
scope. The Access attribute would be illegal in this case (see
3.10.2).