DEFSTRUCT redefinition can crash ABCL on MAKE-STRUCT

[mseddon]

CL-USER(1): (defstruct foo x y)
FOO
CL-USER(2): (defstruct foo x y z)
FOO
CL-USER(3): (make-foo :x 1 :y 2 :z 3)
ABCL Debug.assertTrue() assertion failed!
java.lang.Error: ABCL Debug.assertTrue() assertion failed!

at org.armedbear.lisp.Debug.assertTrue(Debug.java:46)
at org.armedbear.lisp.StructureObject?.writeToString(StructureObject?.java

:483)

Multiple DEFSTRUCTs do not change the underlying structure class, but seem to cause StructureObject? to assert if the new (almost ignored) definition had a different number of slots than the old.

For example, while the above example crashes out ABCL, the following example does not:

CL-USER(1): (defstruct foo a b c)
FOO
CL-USER(2): (defstruct foo x y z)
FOO
CL-USER(3): (make-foo :x 1 :y 2 :z 3)
#S(FOO :A 1 :B 2 :C 3)

[Mark Evenson]

Still present:

ABCL Debug.assertTrue() assertion failed!
java.lang.Error: ABCL Debug.assertTrue() assertion failed!
	at org.armedbear.lisp.Debug.assertTrue(Debug.java:46)
	at org.armedbear.lisp.StructureObject.printObject(StructureObject.java:483)
	at org.armedbear.lisp.Primitives$pf__write_to_string.execute(Primitives.java:925)
	at org.armedbear.lisp.Symbol.execute(Symbol.java:785)
	at org.armedbear.lisp.LispThread.execute(LispThread.java:649)
	at org.armedbear.lisp.print_object_10.execute(print-object.lisp:47)
	at org.armedbear.lisp.clos_294.execute(clos.lisp:1976)
	at org.armedbear.lisp.clos_272.execute(clos.lisp:1728)

[Mark Evenson]

Should be fixed; identify test.

[ehuelsmann]

Problem is that we have DEFSTRUCTs in our code; we can't just reject redefinition, because that'd negatively interact with our current bootstrapping procedure.

Analysis of other implementations:

1. SBCL offers a restart Continue/recklessly-continue/Abort
2. clisp just continues

The solution we want to see implemented is: detect differences in definition and offer a restart to continue (change it).

This doesn't affect our bootstrapping since we always define to the same definition.

[ehuelsmann]

(In [14128]) Fix #113 (redefinition of structures can crash ABCL) by failing

the redefinition if the two structure definitions are not equalp.