I've reported the issue upstream:

	https://github.com/Ferada/cl-cffi-gtk/issues/24#issuecomment-428756336

but it could be that the errors comes from the way we run tests.

Here is a copy of the error output during the check phase:

--8<---------------cut here---------------start------------->8---
; compiling (TEST G-SIGNAL-HAS-HANDLER-PENDING ...)

; /gnu/store/3147aza1waksp76pllkifskyym4wmqvg-sbcl-cl-cffi-gtk-0.11.2-1.29443c5/lib/sbcl/test/rtest-gobject-signals-tmpX2JYJDQE.fasl written
; compilation finished in 0:00:00.002
CORRUPTION WARNING in SBCL pid 17(tid 0x7ffff7ff41c0):
Memory fault at (nil) (pc=0x7ffff1339339, sp=0x7ffff6e05b90)
The integrity of this image is possibly compromised.
Continuing with fingers crossed.
Unhandled SB-SYS:MEMORY-FAULT-ERROR in thread #<SB-THREAD:THREAD "main thread" RUNNING
                                                 {10005585B3}>:
  Unhandled memory fault at #x0.

Backtrace for: #<SB-THREAD:THREAD "main thread" RUNNING {10005585B3}>
0: (SB-DEBUG::DEBUGGER-DISABLED-HOOK #<SB-SYS:MEMORY-FAULT-ERROR {1002DA6433}> #<unused argument> :QUIT T)
1: (SB-DEBUG::RUN-HOOK SB-EXT:*INVOKE-DEBUGGER-HOOK* #<SB-SYS:MEMORY-FAULT-ERROR {1002DA6433}>)
2: (INVOKE-DEBUGGER #<SB-SYS:MEMORY-FAULT-ERROR {1002DA6433}>)
3: (ERROR SB-SYS:MEMORY-FAULT-ERROR :ADDRESS 0)
4: (SB-SYS:MEMORY-FAULT-ERROR #<unused argument> #.(SB-SYS:INT-SAP #X00000000))
5: ("foreign function: call_into_lisp")
6: ("foreign function: funcall2")
7: ("foreign function: handle_memory_fault_emulation_trap")
8: ("foreign function: handle_trap")
9: ("foreign function: #x41ABC3")
10: (GOBJECT::CALL-GOBJECT-CONSTRUCTOR "GtkButton" NIL NIL NIL)
11: (GOBJECT::CREATE-GOBJECT-FROM-CLASS #<GOBJECT-CLASS GTK:GTK-BUTTON> NIL)
12: ((:METHOD MAKE-INSTANCE (GOBJECT-CLASS)) #<GOBJECT-CLASS GTK:GTK-BUTTON>) [fast-method]
13: (SB-FASL::LOAD-FASL-GROUP #S(SB-FASL::FASL-INPUT :STREAM #<SB-SYS:FD-STREAM for "file /gnu/store/3147aza1waksp76pllkifskyym4wmqvg-sbcl-cl-cffi-gtk-0.11.2-1.29443c5/lib/sbcl/test/rtest-gobject-signals.fasl" {1002D94E93}> :TABLE #(65 SET *PACKAGE* "GTK-TESTSUITE" #<PACKAGE "IT.BESE.FIVEAM"> MAKE-SUITE #<PACKAGE "GTK-TESTSUITE"> GOBJECT-SIGNALS :IN GOBJECT-SUITE GET-TEST SETF ...) :STACK #(0 MAKE-INSTANCE GTK-BUTTON NIL (SB-INT:SFUNCTION NIL NULL) NIL NULL :IN 21424 CERROR 19128 GET-TEST ...) :NAME-BUFFER #("\0" "GTK-BUTTONNCEG-FUN-TOPLEVEL\0\0\0\0") :DEPRECATED-STUFF NIL :SKIP-UNTIL NIL) NIL)
14: (SB-FASL::LOAD-AS-FASL #<SB-SYS:FD-STREAM for "file /gnu/store/3147aza1waksp76pllkifskyym4wmqvg-sbcl-cl-cffi-gtk-0.11.2-1.29443c5/lib/sbcl/test/rtest-gobject-signals.fasl" {1002D94E93}> NIL NIL)
15: ((FLET SB-FASL::THUNK :IN LOAD))
16: (SB-FASL::CALL-WITH-LOAD-BINDINGS #<CLOSURE (FLET SB-FASL::THUNK :IN LOAD) {7FFFF6E067CB}> #<SB-SYS:FD-STREAM for "file /gnu/store/3147aza1waksp76pllkifskyym4wmqvg-sbcl-cl-cffi-gtk-0.11.2-1.29443c5/lib/sbcl/test/rtest-gobject-signals.fasl" {1002D94E93}>)
17: ((FLET SB-FASL::LOAD-STREAM :IN LOAD) #<SB-SYS:FD-STREAM for "file /gnu/store/3147aza1waksp76pllkifskyym4wmqvg-sbcl-cl-cffi-gtk-0.11.2-1.29443c5/lib/sbcl/test/rtest-gobject-signals.fasl" {1002D94E93}> T)
18: (LOAD #P"/gnu/store/3147aza1waksp76pllkifskyym4wmqvg-sbcl-cl-cffi-gtk-0.11.2-1.29443c5/lib/sbcl/test/rtest-gobject-signals.fasl" :VERBOSE NIL :PRINT NIL :IF-DOES-NOT-EXIST T :EXTERNAL-FORMAT :DEFAULT)
19: (UIOP/UTILITY:CALL-WITH-MUFFLED-CONDITIONS #<CLOSURE (LAMBDA NIL :IN UIOP/LISP-BUILD:LOAD*) {1002D938EB}> ("Overwriting already existing readtable ~S." #(#:FINALIZERS-OFF-WARNING :ASDF-FINALIZERS)))
20: ((SB-PCL::EMF ASDF/ACTION:PERFORM) #<unused argument> #<unused argument> #<ASDF/LISP-ACTION:LOAD-OP > #<ASDF/LISP-ACTION:CL-SOURCE-FILE "cl-cffi-gtk-test" "rtest-gobject-signals">)
21: ((LAMBDA NIL :IN ASDF/ACTION:CALL-WHILE-VISITING-ACTION))
22: ((:METHOD ASDF/ACTION:PERFORM-WITH-RESTARTS (ASDF/LISP-ACTION:LOAD-OP ASDF/LISP-ACTION:CL-SOURCE-FILE)) #<ASDF/LISP-ACTION:LOAD-OP > #<ASDF/LISP-ACTION:CL-SOURCE-FILE "cl-cffi-gtk-test" "rtest-gobject-signals">) [fast-method]
23: ((:METHOD ASDF/ACTION:PERFORM-WITH-RESTARTS :AROUND (T T)) #<ASDF/LISP-ACTION:LOAD-OP > #<ASDF/LISP-ACTION:CL-SOURCE-FILE "cl-cffi-gtk-test" "rtest-gobject-signals">) [fast-method]
24: ((:METHOD ASDF/PLAN:PERFORM-PLAN (T)) #<ASDF/PLAN:SEQUENTIAL-PLAN {1002325373}>) [fast-method]
25: ((FLET SB-C::WITH-IT :IN SB-C::%WITH-COMPILATION-UNIT))
26: ((:METHOD ASDF/PLAN:PERFORM-PLAN :AROUND (T)) #<ASDF/PLAN:SEQUENTIAL-PLAN {1002325373}>) [fast-method]
27: ((:METHOD ASDF/OPERATE:OPERATE (ASDF/OPERATION:OPERATION ASDF/COMPONENT:COMPONENT)) #<ASDF/LISP-ACTION:TEST-OP > #<ASDF/SYSTEM:SYSTEM "cl-cffi-gtk"> :PLAN-CLASS NIL :PLAN-OPTIONS NIL) [fast-method]
28: ((SB-PCL::EMF ASDF/OPERATE:OPERATE) #<unused argument> #<unused argument> #<ASDF/LISP-ACTION:TEST-OP > #<ASDF/SYSTEM:SYSTEM "cl-cffi-gtk">)
29: ((LAMBDA NIL :IN ASDF/OPERATE:OPERATE))
30: ((:METHOD ASDF/OPERATE:OPERATE :AROUND (T T)) #<ASDF/LISP-ACTION:TEST-OP > #<ASDF/SYSTEM:SYSTEM "cl-cffi-gtk">) [fast-method]
31: ((SB-PCL::EMF ASDF/OPERATE:OPERATE) #<unused argument> #<unused argument> ASDF/LISP-ACTION:TEST-OP "cl-cffi-gtk")
32: ((LAMBDA NIL :IN ASDF/OPERATE:OPERATE))
33: ((:METHOD ASDF/OPERATE:OPERATE :AROUND (T T)) ASDF/LISP-ACTION:TEST-OP "cl-cffi-gtk") [fast-method]
34: (ASDF/SESSION:CALL-WITH-ASDF-SESSION #<CLOSURE (LAMBDA NIL :IN ASDF/OPERATE:OPERATE) {10021BAA2B}> :OVERRIDE T :KEY NIL :OVERRIDE-CACHE T :OVERRIDE-FORCING NIL)
35: ((LAMBDA NIL :IN ASDF/OPERATE:OPERATE))
36: (ASDF/SESSION:CALL-WITH-ASDF-SESSION #<CLOSURE (LAMBDA NIL :IN ASDF/OPERATE:OPERATE) {10041D7B0B}> :OVERRIDE NIL :KEY NIL :OVERRIDE-CACHE NIL :OVERRIDE-FORCING NIL)
37: ((:METHOD ASDF/OPERATE:OPERATE :AROUND (T T)) ASDF/LISP-ACTION:TEST-OP "cl-cffi-gtk") [fast-method]
38: (ASDF/OPERATE:TEST-SYSTEM "cl-cffi-gtk")
39: (SB-INT:SIMPLE-EVAL-IN-LEXENV (ASDF/OPERATE:TEST-SYSTEM "cl-cffi-gtk") #<NULL-LEXENV>)
40: (EVAL (ASDF/OPERATE:TEST-SYSTEM "cl-cffi-gtk"))
41: (SB-IMPL::PROCESS-EVAL/LOAD-OPTIONS ((:EVAL . "(require :asdf)") (:EVAL . #<(SIMPLE-ARRAY CHARACTER (344)) (let ((*package* (find-package :asdf))) (load "/gnu/store/3147aza1waksp76pllkifskyym4wmqvg-sbcl-cl-cffi-gtk-0.11.2-1.29443c5/share/common-lisp/sbcl-source/cl-cffi-gtk/gtk/cl-cffi-gtk.asd") (load "/gnu... {1001C2D0BF}>) (:EVAL . "(asdf:test-system \"cl-cffi-gtk\")") (:QUIT)))
42: (SB-IMPL::TOPLEVEL-INIT)
43: ((FLET SB-UNIX::BODY :IN SB-EXT:SAVE-LISP-AND-DIE))
44: ((FLET "WITHOUT-INTERRUPTS-BODY-27" :IN SB-EXT:SAVE-LISP-AND-DIE))
45: ((LABELS SB-IMPL::RESTART-LISP :IN SB-EXT:SAVE-LISP-AND-DIE))
; compiling (TEST G-SIGNAL-HAS-HANDLER-PENDING ...)

; /gnu/store/3147aza1waksp76pllkifskyym4wmqvg-sbcl-cl-cffi-gtk-0.11.2-1.29443c5/lib/sbcl/test/rtest-gobject-signals-tmpX2JYJDQE.fasl written
; compilation finished in 0:00:00.002
CORRUPTION WARNING in SBCL pid 17(tid 0x7ffff7ff41c0):
Memory fault at (nil) (pc=0x7ffff1339339, sp=0x7ffff6e05b90)
The integrity of this image is possibly compromised.
Continuing with fingers crossed.
Unhandled SB-SYS:MEMORY-FAULT-ERROR in thread #<SB-THREAD:THREAD "main thread" RUNNING
                                                 {10005585B3}>:
  Unhandled memory fault at #x0.

Backtrace for: #<SB-THREAD:THREAD "main thread" RUNNING {10005585B3}>
0: (SB-DEBUG::DEBUGGER-DISABLED-HOOK #<SB-SYS:MEMORY-FAULT-ERROR {1002DA6433}> #<unused argument> :QUIT T)
1: (SB-DEBUG::RUN-HOOK SB-EXT:*INVOKE-DEBUGGER-HOOK* #<SB-SYS:MEMORY-FAULT-ERROR {1002DA6433}>)
2: (INVOKE-DEBUGGER #<SB-SYS:MEMORY-FAULT-ERROR {1002DA6433}>)
3: (ERROR SB-SYS:MEMORY-FAULT-ERROR :ADDRESS 0)
4: (SB-SYS:MEMORY-FAULT-ERROR #<unused argument> #.(SB-SYS:INT-SAP #X00000000))
5: ("foreign function: call_into_lisp")
6: ("foreign function: funcall2")
7: ("foreign function: handle_memory_fault_emulation_trap")
8: ("foreign function: handle_trap")
9: ("foreign function: #x41ABC3")
10: (GOBJECT::CALL-GOBJECT-CONSTRUCTOR "GtkButton" NIL NIL NIL)
11: (GOBJECT::CREATE-GOBJECT-FROM-CLASS #<GOBJECT-CLASS GTK:GTK-BUTTON> NIL)
12: ((:METHOD MAKE-INSTANCE (GOBJECT-CLASS)) #<GOBJECT-CLASS GTK:GTK-BUTTON>) [fast-method]
13: (SB-FASL::LOAD-FASL-GROUP #S(SB-FASL::FASL-INPUT :STREAM #<SB-SYS:FD-STREAM for "file /gnu/store/3147aza1waksp76pllkifskyym4wmqvg-sbcl-cl-cffi-gtk-0.11.2-1.29443c5/lib/sbcl/test/rtest-gobject-signals.fasl" {1002D94E93}> :TABLE #(65 SET *PACKAGE* "GTK-TESTSUITE" #<PACKAGE "IT.BESE.FIVEAM"> MAKE-SUITE #<PACKAGE "GTK-TESTSUITE"> GOBJECT-SIGNALS :IN GOBJECT-SUITE GET-TEST SETF ...) :STACK #(0 MAKE-INSTANCE GTK-BUTTON NIL (SB-INT:SFUNCTION NIL NULL) NIL NULL :IN 21424 CERROR 19128 GET-TEST ...) :NAME-BUFFER #("\0" "GTK-BUTTONNCEG-FUN-TOPLEVEL\0\0\0\0") :DEPRECATED-STUFF NIL :SKIP-UNTIL NIL) NIL)
14: (SB-FASL::LOAD-AS-FASL #<SB-SYS:FD-STREAM for "file /gnu/store/3147aza1waksp76pllkifskyym4wmqvg-sbcl-cl-cffi-gtk-0.11.2-1.29443c5/lib/sbcl/test/rtest-gobject-signals.fasl" {1002D94E93}> NIL NIL)
15: ((FLET SB-FASL::THUNK :IN LOAD))
16: (SB-FASL::CALL-WITH-LOAD-BINDINGS #<CLOSURE (FLET SB-FASL::THUNK :IN LOAD) {7FFFF6E067CB}> #<SB-SYS:FD-STREAM for "file /gnu/store/3147aza1waksp76pllkifskyym4wmqvg-sbcl-cl-cffi-gtk-0.11.2-1.29443c5/lib/sbcl/test/rtest-gobject-signals.fasl" {1002D94E93}>)
17: ((FLET SB-FASL::LOAD-STREAM :IN LOAD) #<SB-SYS:FD-STREAM for "file /gnu/store/3147aza1waksp76pllkifskyym4wmqvg-sbcl-cl-cffi-gtk-0.11.2-1.29443c5/lib/sbcl/test/rtest-gobject-signals.fasl" {1002D94E93}> T)
18: (LOAD #P"/gnu/store/3147aza1waksp76pllkifskyym4wmqvg-sbcl-cl-cffi-gtk-0.11.2-1.29443c5/lib/sbcl/test/rtest-gobject-signals.fasl" :VERBOSE NIL :PRINT NIL :IF-DOES-NOT-EXIST T :EXTERNAL-FORMAT :DEFAULT)
19: (UIOP/UTILITY:CALL-WITH-MUFFLED-CONDITIONS #<CLOSURE (LAMBDA NIL :IN UIOP/LISP-BUILD:LOAD*) {1002D938EB}> ("Overwriting already existing readtable ~S." #(#:FINALIZERS-OFF-WARNING :ASDF-FINALIZERS)))
20: ((SB-PCL::EMF ASDF/ACTION:PERFORM) #<unused argument> #<unused argument> #<ASDF/LISP-ACTION:LOAD-OP > #<ASDF/LISP-ACTION:CL-SOURCE-FILE "cl-cffi-gtk-test" "rtest-gobject-signals">)
21: ((LAMBDA NIL :IN ASDF/ACTION:CALL-WHILE-VISITING-ACTION))
22: ((:METHOD ASDF/ACTION:PERFORM-WITH-RESTARTS (ASDF/LISP-ACTION:LOAD-OP ASDF/LISP-ACTION:CL-SOURCE-FILE)) #<ASDF/LISP-ACTION:LOAD-OP > #<ASDF/LISP-ACTION:CL-SOURCE-FILE "cl-cffi-gtk-test" "rtest-gobject-signals">) [fast-method]
23: ((:METHOD ASDF/ACTION:PERFORM-WITH-RESTARTS :AROUND (T T)) #<ASDF/LISP-ACTION:LOAD-OP > #<ASDF/LISP-ACTION:CL-SOURCE-FILE "cl-cffi-gtk-test" "rtest-gobject-signals">) [fast-method]
24: ((:METHOD ASDF/PLAN:PERFORM-PLAN (T)) #<ASDF/PLAN:SEQUENTIAL-PLAN {1002325373}>) [fast-method]
25: ((FLET SB-C::WITH-IT :IN SB-C::%WITH-COMPILATION-UNIT))
26: ((:METHOD ASDF/PLAN:PERFORM-PLAN :AROUND (T)) #<ASDF/PLAN:SEQUENTIAL-PLAN {1002325373}>) [fast-method]
27: ((:METHOD ASDF/OPERATE:OPERATE (ASDF/OPERATION:OPERATION ASDF/COMPONENT:COMPONENT)) #<ASDF/LISP-ACTION:TEST-OP > #<ASDF/SYSTEM:SYSTEM "cl-cffi-gtk"> :PLAN-CLASS NIL :PLAN-OPTIONS NIL) [fast-method]
28: ((SB-PCL::EMF ASDF/OPERATE:OPERATE) #<unused argument> #<unused argument> #<ASDF/LISP-ACTION:TEST-OP > #<ASDF/SYSTEM:SYSTEM "cl-cffi-gtk">)
29: ((LAMBDA NIL :IN ASDF/OPERATE:OPERATE))
30: ((:METHOD ASDF/OPERATE:OPERATE :AROUND (T T)) #<ASDF/LISP-ACTION:TEST-OP > #<ASDF/SYSTEM:SYSTEM "cl-cffi-gtk">) [fast-method]
31: ((SB-PCL::EMF ASDF/OPERATE:OPERATE) #<unused argument> #<unused argument> ASDF/LISP-ACTION:TEST-OP "cl-cffi-gtk")
32: ((LAMBDA NIL :IN ASDF/OPERATE:OPERATE))
33: ((:METHOD ASDF/OPERATE:OPERATE :AROUND (T T)) ASDF/LISP-ACTION:TEST-OP "cl-cffi-gtk") [fast-method]
34: (ASDF/SESSION:CALL-WITH-ASDF-SESSION #<CLOSURE (LAMBDA NIL :IN ASDF/OPERATE:OPERATE) {10021BAA2B}> :OVERRIDE T :KEY NIL :OVERRIDE-CACHE T :OVERRIDE-FORCING NIL)
35: ((LAMBDA NIL :IN ASDF/OPERATE:OPERATE))
36: (ASDF/SESSION:CALL-WITH-ASDF-SESSION #<CLOSURE (LAMBDA NIL :IN ASDF/OPERATE:OPERATE) {10041D7B0B}> :OVERRIDE NIL :KEY NIL :OVERRIDE-CACHE NIL :OVERRIDE-FORCING NIL)
37: ((:METHOD ASDF/OPERATE:OPERATE :AROUND (T T)) ASDF/LISP-ACTION:TEST-OP "cl-cffi-gtk") [fast-method]
38: (ASDF/OPERATE:TEST-SYSTEM "cl-cffi-gtk")
39: (SB-INT:SIMPLE-EVAL-IN-LEXENV (ASDF/OPERATE:TEST-SYSTEM "cl-cffi-gtk") #<NULL-LEXENV>)
40: (EVAL (ASDF/OPERATE:TEST-SYSTEM "cl-cffi-gtk"))
41: (SB-IMPL::PROCESS-EVAL/LOAD-OPTIONS ((:EVAL . "(require :asdf)") (:EVAL . #<(SIMPLE-ARRAY CHARACTER (344)) (let ((*package* (find-package :asdf))) (load "/gnu/store/3147aza1waksp76pllkifskyym4wmqvg-sbcl-cl-cffi-gtk-0.11.2-1.29443c5/share/common-lisp/sbcl-source/cl-cffi-gtk/gtk/cl-cffi-gtk.asd") (load "/gnu... {1001C2D0BF}>) (:EVAL . "(asdf:test-system \"cl-cffi-gtk\")") (:QUIT)))
42: (SB-IMPL::TOPLEVEL-INIT)
43: ((FLET SB-UNIX::BODY :IN SB-EXT:SAVE-LISP-AND-DIE))
44: ((FLET "WITHOUT-INTERRUPTS-BODY-27" :IN SB-EXT:SAVE-LISP-AND-DIE))
45: ((LABELS SB-IMPL::RESTART-LISP :IN SB-EXT:SAVE-LISP-AND-DIE))

--8<---------------cut here---------------end--------------->8---

-- 
Pierre Neidhardt
https://ambrevar.xyz/