CFFI is warning of deprecated useage of bare references to struct types

[jkcunningham]

This error message showing up in several projects I maintain which employ cl-gd:

;; STYLE-WARNING:
;; bare references to struct types are deprecated. Please use (:POINTER (:STRUCT CL-GD::GD-IMAGE))
;; or (:STRUCT CL-GD::GD-IMAGE) instead.

I've put together a simple case which exhibits the behavior. It seems to be the WITH-THICKNESS macro causing the warning in this case:

(ql:quickload "cl-gd")
(use-package :cl-gd)

(let* ((x1 -86)
(x2 529)
(y1 -0.13)
(y2 1.16)
(xv '(0.0 1.0 2.0 3.0 4.0))
(yv '(0.99 0.12 0.66 0.24 0.075)))
(with-image* (500 250)
(allocate-color 255 255 255)
(let ((c (allocate-color 0 0 255)))
(with-transformation (:x1 x1 :x2 x2 :y1 y1 :y2 y2)
(with-thickness (1)
(mapl #'(lambda (x y)
(when (and (cdr x) (cdr y))
(draw-line (car x) (car y) (cadr x) (cadr y) :color c))) xv yv))
(write-image-to-file "test.png" :if-exists :supersede)))))

If you take out the with-thickness macro call the message disappears.

I posted this to both the cl-gd-devel and cffi-devel lists. Liam Healy from the latter sent this response:

"It's harmless, it's just telling you that the syntax that cl-gd uses for structure arguments will eventually (in a future version of CFFI) not work. The messages describes the problem. The structure is specified as cl-gd::gd-image in a function argument or return value. In the old versions of CFFI, that was interpreted as a pointer to that structure, because there was no other possibility. Now structures can also be passed/returned by value using cffi-libffi, so you have to say explicitly as the error message indicates. They might also need to change the use of #'mem-aref (which before returned a pointer to the structure but now returns the structure itself) into a #'mem-aptr."

Much obliged.
--Jeff Cunningham

[hanshuebner]

I analysed the problem and found it to be twofold: CFFI-UFFI-COMPAT does not provision for passing struct and struct pointer parameters correctly, and CL-GD does not try to either.

I attempted to fix the problem in CFFI (https://github.com/edicl/cffi) and also (https://github.com/edicl/cl-gd/tree/cffi-uffi-warning) but I was not able to completely get it right. I may get back to this at some point, but for now, I'm leaving it to be fixed when it really causes issues other than the warning.

[bobbysmith007]

Thanks for putting some work into this on CFFI-UFFI-COMPAT. I have been running clsql with this package and am suddenly getting tons of style-warnings (after a quicklisp upgrade).

This is how I resolved the issue: cffi/cffi#35

[jkcunningham]

On 02/08/2014 11:34 PM, Hans Hübner wrote:

I analysed the problem and found it to be twofold: CFFI-UFFI-COMPAT
does not provision for passing struct and struct pointer parameters
correctly, and CL-GD does not try to either.

I attempted to fix the problem in CFFI (https://github.com/edicl/cffi)
and also (https://github.com/edicl/cl-gd/tree/cffi-uffi-warning) but I
was not able to completely get it right. I may get back to this at
some point, but for now, I'm leaving it to be fixed when it really
causes issues other than the warning.

—
Reply to this email directly or view it on GitHub
#6 (comment).

Is there any chance your changes have broken hunchentoot? I just did a
fresh install of quicklisp on a VPS and hunchentoot install died like this:

215,969 bytes in 0.17 seconds (1205.18KB/sec)
; Loading "hunchentoot"
[package bordeaux-threads]........................
[package usocket].................................
[package rfc2388].................................
[package md5].....................................
[package trivial-garbage].........................
[package impl-specific-gray]......................
[package trivial-gray-streams]....................
[package flexi-streams]...........................
..................................................
..................................................
[package cl+ssl]..........
; file:
/home/jcunningham/quicklisp/dists/quicklisp/software/cl+ssl-20140211-git/bio.lisp
; in: DEFUN MAKE-BIO-LISP-METHOD
; (SETF (CFFI:FOREIGN-SLOT-VALUE CL+SSL::M '(:STRUCT
CL+SSL::BIO-METHOD) 'TYPE)
; CL+SSL::+BIO-TYPE-SOCKET+)
; --> LET* MULTIPLE-VALUE-BIND LET PROGN
; ==>
; (CFFI::FOREIGN-SLOT-SET #:STORE1 CL+SSL::M '(:STRUCT CL+SSL::BIO-METHOD)
; 'TYPE)
;
; caught ERROR:
; during compiler-macroexpansion of (CFFI::FOREIGN-SLOT-SET #:STORE1 M
...). Use
; BREAK-ON-SIGNALS to intercept:
;
; Unknown CFFI type: :STRUCT.

; (SETF (CL+SSL::SLOT 'CL+SSL::NAME) (CFFI:FOREIGN-STRING-ALLOC "lisp"))
; --> LET* MULTIPLE-VALUE-BIND LET PROGN
; ==>
; (CFFI::FOREIGN-SLOT-SET #:STORE7 CL+SSL::M '(:STRUCT CL+SSL::BIO-METHOD)
; 'CL+SSL::NAME)
;
; caught ERROR:
; during compiler-macroexpansion of (CFFI::FOREIGN-SLOT-SET #:STORE7 M
...). Use
; BREAK-ON-SIGNALS to intercept:
;
; Unknown CFFI type: :STRUCT.

; (SETF (CL+SSL::SLOT 'CL+SSL::BWRITE) (CFFI:CALLBACK
CL+SSL::LISP-WRITE))
; --> LET* MULTIPLE-VALUE-BIND LET PROGN
; ==>
; (CFFI::FOREIGN-SLOT-SET #:STORE9 CL+SSL::M '(:STRUCT CL+SSL::BIO-METHOD)
; 'CL+SSL::BWRITE)
;
; caught ERROR:
; during compiler-macroexpansion of (CFFI::FOREIGN-SLOT-SET #:STORE9 M
...). Use
; BREAK-ON-SIGNALS to intercept:
;
; Unknown CFFI type: :STRUCT.

; (SETF (CL+SSL::SLOT 'CL+SSL::BREAD) (CFFI:CALLBACK CL+SSL::LISP-READ))
; --> LET* MULTIPLE-VALUE-BIND LET PROGN
; ==>
; (CFFI::FOREIGN-SLOT-SET #:STORE11 CL+SSL::M '(:STRUCT
CL+SSL::BIO-METHOD)
; 'CL+SSL::BREAD)
;
; caught ERROR:
; during compiler-macroexpansion of (CFFI::FOREIGN-SLOT-SET #:STORE11
M ...). Use
; BREAK-ON-SIGNALS to intercept:
;
; Unknown CFFI type: :STRUCT.

; (SETF (CL+SSL::SLOT 'CL+SSL::BPUTS) (CFFI:CALLBACK CL+SSL::LISP-PUTS))
; --> LET* MULTIPLE-VALUE-BIND LET PROGN
; ==>
; (CFFI::FOREIGN-SLOT-SET #:STORE13 CL+SSL::M '(:STRUCT
CL+SSL::BIO-METHOD)
; 'CL+SSL::BPUTS)
;
; caught ERROR:
; during compiler-macroexpansion of (CFFI::FOREIGN-SLOT-SET #:STORE13
M ...). Use
; BREAK-ON-SIGNALS to intercept:
;
; Unknown CFFI type: :STRUCT.

; (SETF (CL+SSL::SLOT 'CL+SSL::BGETS) (CFFI-SYS:NULL-POINTER))
; --> LET* MULTIPLE-VALUE-BIND LET PROGN
; ==>
; (CFFI::FOREIGN-SLOT-SET #:STORE15 CL+SSL::M '(:STRUCT
CL+SSL::BIO-METHOD)
; 'CL+SSL::BGETS)
;
; caught ERROR:
; during compiler-macroexpansion of (CFFI::FOREIGN-SLOT-SET #:STORE15
M ...). Use
; BREAK-ON-SIGNALS to intercept:
;
; Unknown CFFI type: :STRUCT.

; (SETF (CL+SSL::SLOT 'CL+SSL::CTRL) (CFFI:CALLBACK CL+SSL::LISP-CTRL))
; --> LET* MULTIPLE-VALUE-BIND LET PROGN
; ==>
; (CFFI::FOREIGN-SLOT-SET #:STORE17 CL+SSL::M '(:STRUCT
CL+SSL::BIO-METHOD)
; 'CL+SSL::CTRL)
;
; caught ERROR:
; during compiler-macroexpansion of (CFFI::FOREIGN-SLOT-SET #:STORE17
M ...). Use
; BREAK-ON-SIGNALS to intercept:
;
; Unknown CFFI type: :STRUCT.

; (SETF (CL+SSL::SLOT 'CL+SSL::CREATE) (CFFI:CALLBACK
CL+SSL::LISP-CREATE))
; --> LET* MULTIPLE-VALUE-BIND LET PROGN
; ==>
; (CFFI::FOREIGN-SLOT-SET #:STORE19 CL+SSL::M '(:STRUCT
CL+SSL::BIO-METHOD)
; 'CL+SSL::CREATE)
;
; caught ERROR:
; during compiler-macroexpansion of (CFFI::FOREIGN-SLOT-SET #:STORE19
M ...). Use
; BREAK-ON-SIGNALS to intercept:
;
; Unknown CFFI type: :STRUCT.

; (SETF (CL+SSL::SLOT 'CL+SSL::DESTROY) (CFFI:CALLBACK
CL+SSL::LISP-DESTROY))
; --> LET* MULTIPLE-VALUE-BIND LET PROGN
; ==>
; (CFFI::FOREIGN-SLOT-SET #:STORE21 CL+SSL::M '(:STRUCT
CL+SSL::BIO-METHOD)
; 'CL+SSL::DESTROY)
;
; caught ERROR:
; during compiler-macroexpansion of (CFFI::FOREIGN-SLOT-SET #:STORE21
M ...). Use
; BREAK-ON-SIGNALS to intercept:
;
; Unknown CFFI type: :STRUCT.

; (SETF (CL+SSL::SLOT 'CL+SSL::CALLBACK-CTRL) (CFFI-SYS:NULL-POINTER))
; --> LET* MULTIPLE-VALUE-BIND LET PROGN
; ==>
; (CFFI::FOREIGN-SLOT-SET #:STORE23 CL+SSL::M '(:STRUCT
CL+SSL::BIO-METHOD)
; 'CL+SSL::CALLBACK-CTRL)
;
; caught ERROR:
; during compiler-macroexpansion of (CFFI::FOREIGN-SLOT-SET #:STORE23
M ...). Use
; BREAK-ON-SIGNALS to intercept:
;
; Unknown CFFI type: :STRUCT.

; (CFFI:FOREIGN-ALLOC '(:STRUCT CL+SSL::BIO-METHOD))
;
; caught ERROR:
; during compiler-macroexpansion of (CFFI:FOREIGN-ALLOC '(:STRUCT
BIO-METHOD)).
; Use BREAK-ON-SIGNALS to intercept:
;
; Unknown CFFI type: :STRUCT.

; in: DEFUN CLEAR-RETRY-FLAGS
; (SETF (CFFI:FOREIGN-SLOT-VALUE CL+SSL::BIO '(:STRUCT CL+SSL::BIO)
; 'CL+SSL::FLAGS)
; (LOGANDC2
; (CFFI:FOREIGN-SLOT-VALUE CL+SSL::BIO '(:STRUCT CL+SSL::BIO)
; 'CL+

Regards,
--Jeff

[jimka2001]

I'm getting 100s/1000s of these warnings as well using gtk. It would be nice if I could fix it, work around, or suppress the warnings as they potentially hide other important output.

STYLE-WARNING:
bare references to struct types are deprecated. Please use (:POINTER
(:STRUCT
GTK::TREE-ITER-CSTRUCT)) or (:STRUCT
GTK::TREE-ITER-CSTRUCT) instead.

STYLE-WARNING:
bare references to struct types are deprecated. Please use (:POINTER
(:STRUCT
GTK::TREE-ITER-CSTRUCT)) or (:STRUCT
GTK::TREE-ITER-CSTRUCT) instead.

[jimka2001]

I've created a pull-request for CFFI which simply suppresses the style warning.
cffi/cffi#61