bug#21466: [PATCH] Avoid defining (temporarily) vars and functions

[Stefan Kangas]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> Package: Emacs
> Version: 25.0.50
>
>
> CC-mode currently defines various non-CC-mode variables and functions
> with dummy values, as a way to avoid byte-compiler warnings when using
> those external vars/functions.
>
> Since this is dangerous business, CC-mode has to be extra careful to
> undo such settings when they're not needed any more.
>
> It might have made sense back in the days when the byte-compiler did not
> offer built-in ways to silence those warnings, but nowadays we can
> do better.
>
> Any objections to the patch below (which also removes the unused
> cc-bytecomp-put, while we're at it)?

Hi Alan,

This patch was sent to the bug list in 2015, but it seems like it
never got a reply at the time.

Assuming this patch is still relevant, could you please take a look?

Best regards,
Stefan Kangas

> 2015-09-12  Stefan Monnier  <monnier@iro.umontreal.ca>
>
>       * lisp/progmodes/cc-bytecomp.el: Use newer compiler-silencers.
>       (cc-bytecomp-defvar): Use just (defvar <foo>) when that is known to
>       silence the byte-compiler warnings.
>       (cc-bytecomp-defun): Use just (declare-function <foo>) when that is
>       known to silence the byte-compiler warnings.
>       (cc-bytecomp-boundp, cc-bytecomp-fboundp): Change accordingly.
>       (cc-bytecomp-put): Remove, unused.
>       (cc-bytecomp-original-properties): Remove var.
>       (cc-bytecomp-setup-environment, cc-bytecomp-restore-environment):
>       Don't use cc-bytecomp-original-properties any more.
>
>
> diff --git a/lisp/progmodes/cc-bytecomp.el b/lisp/progmodes/cc-bytecomp.el
> index 81b7a82..fff2a9e 100644
> --- a/lisp/progmodes/cc-bytecomp.el
> +++ b/lisp/progmodes/cc-bytecomp.el
> @@ -75,12 +75,10 @@
>  
>  (defvar cc-bytecomp-unbound-variables nil)
>  (defvar cc-bytecomp-original-functions nil)
> -(defvar cc-bytecomp-original-properties nil)
>  (defvar cc-bytecomp-loaded-files nil)
>  
>  (setq cc-bytecomp-unbound-variables nil)
>  (setq cc-bytecomp-original-functions nil)
> -(setq cc-bytecomp-original-properties nil)
>  (setq cc-bytecomp-loaded-files nil)
>  
>  (defvar cc-bytecomp-environment-set nil)
> @@ -173,16 +171,6 @@ perhaps a `cc-bytecomp-restore-environment' is forgotten 
> somewhere"))
>                 (cc-bytecomp-debug-msg
>                  "cc-bytecomp-setup-environment: Covered function %s" fun))))
>         (setq p (cdr p)))
> -     (setq p cc-bytecomp-original-properties)
> -     (while p
> -       (let ((sym (car (car (car p))))
> -             (prop (cdr (car (car p))))
> -             (tempdef (car (cdr (car p)))))
> -         (put sym prop tempdef)
> -         (cc-bytecomp-debug-msg
> -          "cc-bytecomp-setup-environment: Bound property %s for %s to %s"
> -          prop sym tempdef))
> -       (setq p (cdr p)))
>       (setq cc-bytecomp-environment-set t)
>       (cc-bytecomp-debug-msg
>        "cc-bytecomp-setup-environment: Done"))))
> @@ -232,22 +220,6 @@ perhaps a `cc-bytecomp-restore-environment' is forgotten 
> somewhere"))
>                  "cc-bytecomp-restore-environment: Not restoring function %s"
>                  fun))))
>         (setq p (cdr p)))
> -     (setq p cc-bytecomp-original-properties)
> -     (while p
> -       (let ((sym (car (car (car p))))
> -             (prop (cdr (car (car p))))
> -             (tempdef (car (cdr (car p))))
> -             (origdef (cdr (cdr (car p)))))
> -         (if (eq (get sym prop) tempdef)
> -             (progn
> -               (put sym prop origdef)
> -               (cc-bytecomp-debug-msg
> -                "cc-bytecomp-restore-environment: Restored property %s for 
> %s to %s"
> -                prop sym origdef))
> -           (cc-bytecomp-debug-msg
> -            "cc-bytecomp-restore-environment: Not restoring property %s for 
> %s"
> -            prop sym)))
> -       (setq p (cdr p)))
>       (setq cc-bytecomp-environment-set nil)
>       (cc-bytecomp-debug-msg
>        "cc-bytecomp-restore-environment: Done"))))
> @@ -348,25 +320,28 @@ afterwards.  Don't use within `eval-when-compile'."
>       (eval-when-compile (cc-bytecomp-setup-environment))))
>  
>  (defmacro cc-bytecomp-defvar (var)
> -  "Binds the symbol as a variable during compilation of the file,
> +  "Bind the symbol as a variable during compilation of the file,
>  to silence the byte compiler.  Don't use within `eval-when-compile'."
> -  `(eval-when-compile
> -     (if (boundp ',var)
> -      (cc-bytecomp-debug-msg
> -       "cc-bytecomp-defvar: %s bound already as variable" ',var)
> -       (if (not (memq ',var cc-bytecomp-unbound-variables))
> -        (progn
> -          (cc-bytecomp-debug-msg
> -           "cc-bytecomp-defvar: Saving %s (as unbound)" ',var)
> -          (setq cc-bytecomp-unbound-variables
> -                (cons ',var cc-bytecomp-unbound-variables))))
> -       (if (cc-bytecomp-is-compiling)
> -        (progn
> -          (defvar ,var)
> -          (set ',var (intern (concat "cc-bytecomp-ignore-var:"
> -                                     (symbol-name ',var))))
> -          (cc-bytecomp-debug-msg
> -           "cc-bytecomp-defvar: Covered variable %s" ',var))))))
> +  (if (not (featurep 'xemacs))
> +      `(defvar ,var)
> +    ;; Not sure if XEmacs's ‘defvar’ works in the same way.
> +    `(eval-when-compile
> +       (if (boundp ',var)
> +        (cc-bytecomp-debug-msg
> +         "cc-bytecomp-defvar: %s bound already as variable" ',var)
> +      (if (not (memq ',var cc-bytecomp-unbound-variables))
> +          (progn
> +            (cc-bytecomp-debug-msg
> +             "cc-bytecomp-defvar: Saving %s (as unbound)" ',var)
> +            (setq cc-bytecomp-unbound-variables
> +                  (cons ',var cc-bytecomp-unbound-variables))))
> +      (if (cc-bytecomp-is-compiling)
> +          (progn
> +            (defvar ,var)
> +            (set ',var (intern (concat "cc-bytecomp-ignore-var:"
> +                                       (symbol-name ',var))))
> +            (cc-bytecomp-debug-msg
> +             "cc-bytecomp-defvar: Covered variable %s" ',var)))))))
>  
>  (defmacro cc-bytecomp-defun (fun)
>    "Bind the symbol as a function during compilation of the file,
> @@ -377,48 +352,33 @@ definition.  That means that this macro will not shut 
> up warnings
>  about incorrect number of arguments.  It's dangerous to try to replace
>  existing functions since the byte compiler might need the definition
>  at compile time, e.g. for macros and inline functions."
> -  `(eval-when-compile
> -     (if (fboundp ',fun)
> -      (cc-bytecomp-debug-msg
> -       "cc-bytecomp-defun: %s bound already as function" ',fun)
> -       (if (not (assq ',fun cc-bytecomp-original-functions))
> -        (progn
> -          (cc-bytecomp-debug-msg
> -           "cc-bytecomp-defun: Saving %s (as unbound)" ',fun)
> -          (setq cc-bytecomp-original-functions
> -                (cons (list ',fun nil 'unbound)
> -                      cc-bytecomp-original-functions))))
> -       (if (cc-bytecomp-is-compiling)
> -        (progn
> -          (fset ',fun (intern (concat "cc-bytecomp-ignore-fun:"
> -                                      (symbol-name ',fun))))
> -          (cc-bytecomp-debug-msg
> -           "cc-bytecomp-defun: Covered function %s" ',fun))))))
> -
> -(defmacro cc-bytecomp-put (symbol propname value)
> -  "Set a property on a symbol during compilation (and evaluation) of
> -the file.  Don't use outside `eval-when-compile'."
> -  `(eval-when-compile
> -     (if (not (assoc (cons ,symbol ,propname) 
> cc-bytecomp-original-properties))
> -      (progn
> +  (if (fboundp 'declare-function)
> +      `(declare-function ,fun nil)
> +    `(eval-when-compile
> +       (if (fboundp ',fun)
>          (cc-bytecomp-debug-msg
> -         "cc-bytecomp-put: Saving property %s for %s with value %s"
> -         ,propname ,symbol (get ,symbol ,propname))
> -        (setq cc-bytecomp-original-properties
> -              (cons (cons (cons ,symbol ,propname)
> -                          (cons ,value (get ,symbol ,propname)))
> -                    cc-bytecomp-original-properties))))
> -     (put ,symbol ,propname ,value)
> -     (cc-bytecomp-debug-msg
> -      "cc-bytecomp-put: Bound property %s for %s to %s"
> -      ,propname ,symbol ,value)))
> +         "cc-bytecomp-defun: %s bound already as function" ',fun)
> +      (if (not (assq ',fun cc-bytecomp-original-functions))
> +          (progn
> +            (cc-bytecomp-debug-msg
> +             "cc-bytecomp-defun: Saving %s (as unbound)" ',fun)
> +            (setq cc-bytecomp-original-functions
> +                  (cons (list ',fun nil 'unbound)
> +                        cc-bytecomp-original-functions))))
> +      (if (cc-bytecomp-is-compiling)
> +          (progn
> +            (fset ',fun (intern (concat "cc-bytecomp-ignore-fun:"
> +                                        (symbol-name ',fun))))
> +            (cc-bytecomp-debug-msg
> +             "cc-bytecomp-defun: Covered function %s" ',fun)))))))
>  
>  (defmacro cc-bytecomp-boundp (symbol)
>    "Return non-nil if the given symbol is bound as a variable outside
>  the compilation.  This is the same as using `boundp' but additionally
>  exclude any variables that have been bound during compilation with
>  `cc-bytecomp-defvar'."
> -  (if (and (cc-bytecomp-is-compiling)
> +  (if (and (featurep 'xemacs)
> +        (cc-bytecomp-is-compiling)
>          (memq (car (cdr symbol)) cc-bytecomp-unbound-variables))
>        nil
>      `(boundp ,symbol)))
> @@ -429,7 +389,8 @@ the compilation.  This is the same as using `fboundp' but 
> additionally
>  exclude any functions that have been bound during compilation with
>  `cc-bytecomp-defun'."
>    (let (fun-elem)
> -    (if (and (cc-bytecomp-is-compiling)
> +    (if (and (not (fboundp 'declare-function))
> +          (cc-bytecomp-is-compiling)
>            (setq fun-elem (assq (car (cdr symbol))
>                                 cc-bytecomp-original-functions))
>            (eq (elt fun-elem 2) 'unbound))