None.
The intent of the abort restart is to allow return to the
innermost “command level.” Implementors are encouraged to make
sure that there is always a restart named abort
around any user code so that user code can call abort
at any time and expect something reasonable to happen;
exactly what the reasonable thing is may vary somewhat. Typically,
in an interactive listener, the invocation of abort
returns to the Lisp reader phase of the Lisp read-eval-print loop,
though in some batch or multi-processing
situations there may be situations in which having it kill the running
process is more appropriate.
Section 9.1.4.2 (Restarts), Section 9.1.4.2.2 (Interfaces to Restarts), invoke-restart, abort (function)