layout depth conflict with custom funcallable sequence class

[Christophe]

I'm trying to replicate the first example from "User-extensible sequences in Common Lisp" but SBCL master (e75515a6a) and SBCL 2.4.0 (both built with "--fancy") report an error with these two definitions (the behavior is the same whether or not I define "queue" first or second):

(defclass queue (standard-object sequence)
    ((%data :accessor %queue-data)
     (%pointer :accessor %queue-pointer)))

(defclass funcallable-queue (queue sb-mop:funcallable-standard-object)
  ()
  (:metaclass sb-mop:funcallable-standard-class))

When the second class is being defined, an error shows up as follows:

layout depth conflict: #(#<SB-KERNEL:LAYOUT (ID=340) for T {50101003}>
                         #<SB-KERNEL:LAYOUT (ID=129) for SEQUENCE {50101233}>
                         #<SB-KERNEL:LAYOUT (ID=341) for SB-PCL::SLOT-OBJECT {50111463}>
                         #<SB-KERNEL:LAYOUT (ID=342) for STANDARD-OBJECT {501134D3}>
                         #<SB-KERNEL:LAYOUT (ID=128) for FUNCTION {50101153}>
                         #<SB-KERNEL:LAYOUT (ID=343) for SB-MOP:FUNCALLABLE-STANDARD-OBJECT {50113463}>
                         #<SB-KERNEL:LAYOUT (ID=345) for QUEUE {502E5303}>)

I believe the example should still work as presented in the paper, hopefully this is the correct way to write it (I added "sb-mop:" in front of two symbols).

A call to (map () #'describe *) where * stands for the vector of layouts gives:

#<SB-KERNEL:LAYOUT (ID=340) for T {50101003}>
  [structure-object]

Slots with :INSTANCE allocation:
  FLAGS = 0
  CLOS-HASH = 2917193494582000972
  CLASSOID = #<SB-KERNEL:BUILT-IN-CLASSOID T (read-only)>
  INVALID = NIL
  INHERITS = #()
  %INFO = NIL
  EQUALP-IMPL = 0
  STRUCT-SLOT-MAP = 0
  SLOT-TABLE = #(1 NIL)
  ID-WORD0 = 340
  ID-WORD1 = 0
  ID-WORD2 = 0
#<SB-KERNEL:LAYOUT (ID=129) for SEQUENCE {50101233}>
  [structure-object]

Slots with :INSTANCE allocation:
  FLAGS = 8589934848
  CLOS-HASH = 2973156064943342943
  CLASSOID = #<SB-KERNEL:BUILT-IN-CLASSOID SEQUENCE (read-only)>
  INVALID = NIL
  INHERITS = #(#<SB-KERNEL:LAYOUT (ID=340) for T {50101003}>)
  %INFO = NIL
  EQUALP-IMPL = 0
  STRUCT-SLOT-MAP = 0
  SLOT-TABLE = #(1 NIL)
  ID-WORD0 = 129
  ID-WORD1 = 0
  ID-WORD2 = 0
#<SB-KERNEL:LAYOUT (ID=341) for SB-PCL::SLOT-OBJECT {50111463}>
  [structure-object]

Slots with :INSTANCE allocation:
  FLAGS = -8589934592
  CLOS-HASH = 3457679566203737886
  CLASSOID = #<SB-KERNEL:BUILT-IN-CLASSOID SB-PCL::SLOT-OBJECT (read-only)>
  INVALID = NIL
  INHERITS = #(#<SB-KERNEL:LAYOUT (ID=340) for T {50101003}>)
  %INFO = NIL
  EQUALP-IMPL = 0
  STRUCT-SLOT-MAP = 0
  SLOT-TABLE = #(1 NIL)
  ID-WORD0 = 341
  ID-WORD1 = 0
  ID-WORD2 = 0
#<SB-KERNEL:LAYOUT (ID=342) for STANDARD-OBJECT {501134D3}>
  [structure-object]

Slots with :INSTANCE allocation:
  FLAGS = -8589934076
  CLOS-HASH = 3541692201902988558
  CLASSOID = #<SB-KERNEL:STANDARD-CLASSOID STANDARD-OBJECT>
  INVALID = NIL
  INHERITS = #(#<SB-KERNEL:LAYOUT (ID=340) for T {50101003}> #<SB-KERNEL:LAYOUT (ID=341) for SB-PCL::SLOT-OBJECT {50111463}>)
  %INFO = NIL
  EQUALP-IMPL = 0
  STRUCT-SLOT-MAP = 0
  SLOT-TABLE = #(1 NIL)
  ID-WORD0 = 342
  ID-WORD1 = 0
  ID-WORD2 = 0
#<SB-KERNEL:LAYOUT (ID=128) for FUNCTION {50101153}>
  [structure-object]

Slots with :INSTANCE allocation:
  FLAGS = 8589934592
  CLOS-HASH = 3376082816255072221
  CLASSOID = #<SB-KERNEL:BUILT-IN-CLASSOID FUNCTION (read-only)>
  INVALID = NIL
  INHERITS = #(#<SB-KERNEL:LAYOUT (ID=340) for T {50101003}>)
  %INFO = NIL
  EQUALP-IMPL = 0
  STRUCT-SLOT-MAP = 0
  SLOT-TABLE = #(1 NIL)
  ID-WORD0 = 128
  ID-WORD1 = 0
  ID-WORD2 = 0
#<SB-KERNEL:LAYOUT (ID=343) for SB-MOP:FUNCALLABLE-STANDARD-OBJECT {50113463}>
  [structure-object]

Slots with :INSTANCE allocation:
  FLAGS = -8589934076
  CLOS-HASH = 4312183694679772690
  CLASSOID = #<SB-KERNEL:STANDARD-CLASSOID SB-MOP:FUNCALLABLE-STANDARD-OBJECT>
  INVALID = NIL
  INHERITS = #(#<SB-KERNEL:LAYOUT (ID=340) for T {50101003}> #<SB-KERNEL:LAYOUT (ID=128) for FUNCTION {50101153}> #<SB-KERNEL:LAYOUT (ID=341) for SB-PCL::SLOT-OBJECT {50111463}>..
  %INFO = NIL
  EQUALP-IMPL = 0
  STRUCT-SLOT-MAP = 0
  SLOT-TABLE = #(1 NIL)
  ID-WORD0 = 343
  ID-WORD1 = 0
  ID-WORD2 = 0
#<SB-KERNEL:LAYOUT (ID=345) for QUEUE {502E5303}>
  [structure-object]

Slots with :INSTANCE allocation:
  FLAGS = -8589933820
  CLOS-HASH = 2843883459518754746
  CLASSOID = #<SB-KERNEL:STANDARD-CLASSOID QUEUE>
  INVALID = NIL
  INHERITS = #(#<SB-KERNEL:LAYOUT (ID=340) for T {50101003}> #<SB-KERNEL:LAYOUT (ID=129) for SEQUENCE {50101233}> #<SB-KERNEL:LAYOUT (ID=341) for SB-PCL::SLOT-OBJECT {50111463}>..
  %INFO = NIL
  EQUALP-IMPL = 0
  STRUCT-SLOT-MAP = 0
  SLOT-TABLE = #(1 NIL)
  ID-WORD0 = 345
  ID-WORD1 = 0
  ID-WORD2 = 0
NIL

The above is from SBCL 2.4.0, started with --no-userinit. The same happens in the terminal without Slime etc, in which case the *features* are:

(:ARENA-ALLOCATOR :X86-64 :GENCGC :64-BIT :ANSI-CL :COMMON-LISP :ELF
 :IEEE-FLOATING-POINT :LINUX :LITTLE-ENDIAN :PACKAGE-LOCAL-NICKNAMES
 :SB-CORE-COMPRESSION :SB-LDB :SB-PACKAGE-LOCKS :SB-THREAD :SB-UNICODE :SBCL
 :UNIX)

Linux aperture 6.5.0-14-generic #14~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Mon Nov 20 18:15:30 UTC 2 x86_64 x86_64 x86_64 GNU/Linux

Thank you

[Christophe Rhodes (csr21-cantab)]

Thanks for the report. I think I have a fix for this, but we're in the freeze period (and I also need to test it a bit more extensively). Expect a fix to land early next month. (The fix is basically undoing commit 17945c81f96b406d3cbc6bfd73c0090e6ce92c6b, plus adding a lot of test cases :-)