(compile nil '(lambda () (sb-kernel:%array-displaced-p :x)))
==>
Unhandled memory fault at #x0.
[Condition of type SB-SYS:MEMORY-FAULT-ERROR]
Restarts:
0: [RETRY] Retry SLIME REPL evaluation request.
1: [*ABORT] Return to SLIME's top level.
2: [ABORT] abort thread (#<THREAD "new-repl-thread" RUNNING {10315272C3}>)
Backtrace:
0: (SB-KERNEL:CTYPE-OF #<unknown immediate object, lowtag=#b1101, widetag=#x3D {50213E030500053D}>)
1: (SB-C::MAKE-CONSTANT #<unknown immediate object, lowtag=#b1101, widetag=#x3D {50213E030500053D}>) [optional]
2: (SB-C::FIND-CONSTANT #<unknown immediate object, lowtag=#b1101, widetag=#x3D {50213E030500053D}> NIL)
3: (SB-C::REFERENCE-CONSTANT #<SB-C::CTRAN 1 {1031B51213}> #<SB-C::CTRAN 2 {1031B53073}> #<SB-C::LVAR 3 {1031B50C13}> #<unknown immediate object, lowtag=#b1101, widetag=#x3D {50213E030500053D}>)
4: ((FLET "LAMBDA0" :IN "SYS:SRC;COMPILER;IR1UTIL.LISP"))
5: (SB-C::%WITH-IR1-ENVIRONMENT-FROM-NODE #<SB-C::COMBINATION :FUN #<SB-C::REF :LEAF #<SB-C::GLOBAL-VAR :%SOURCE-NAME SB-KERNEL:%ARRAY-DISPLACED-P :TYPE #1=#<SB-KERNEL:FUN-TYPE #> :DEFINED-TYPE #1# :WHE..
6: (SB-C::REPLACE-COMBINATION-WITH-CONSTANT #<unknown immediate object, lowtag=#b1101, widetag=#x3D {50213E030500053D}> #<SB-C::COMBINATION :FUN #<SB-C::REF :LEAF #<SB-C::GLOBAL-VAR :%SOURCE-NAME SB-KER..
7: (SB-C::CONSTANT-FOLD-CALL #<SB-C::COMBINATION :FUN #<SB-C::REF :LEAF #<SB-C::GLOBAL-VAR :%SOURCE-NAME SB-KERNEL:%ARRAY-DISPLACED-P :TYPE #1=#<SB-KERNEL:FUN-TYPE #> :DEFINED-TYPE #1# :WHERE-FROM :DECL..
8: (SB-C::IR1-OPTIMIZE-COMBINATION #<SB-C::COMBINATION :FUN #<SB-C::REF :LEAF #<SB-C::GLOBAL-VAR :%SOURCE-NAME SB-KERNEL:%ARRAY-DISPLACED-P :TYPE #1=#<SB-KERNEL:FUN-TYPE #> :DEFINED-TYPE #1# :WHERE-FROM..
9: (SB-C::IR1-OPTIMIZE #<SB-C:COMPONENT :NAME (LAMBDA NIL) {1031B52713}> NIL)
[...]
It's not to be used on random stuff.