the same as the @code{side-effect-free} property of the function's
symbol, @pxref{Standard Properties}.
+@item (important-return-value @var{val})
+If @var{val} is non-@code{nil}, the byte compiler will warn about
+calls to this function that do not use the returned value. This is the
+same as the @code{important-return-value} property of the function's
+symbol, @pxref{Standard Properties}.
+
@item (speed @var{n})
Specify the value of @code{native-comp-speed} in effect for native
compilation of this function (@pxref{Native-Compilation Variables}).
calls. In addition to byte compiler optimizations, this property is
also used for determining function safety (@pxref{Function Safety}).
+@item important-return-value
+@cindex @code{important-return-value} property
+A non-@code{nil} value makes the byte compiler warn about code that
+calls the named function without using its returned value. This is
+useful for functions where doing so is likely to be a mistake.
+
@item undo-inhibit-region
If non-@code{nil}, the named function prevents the @code{undo} operation
from being restricted to the active region, if @code{undo} is invoked
---
*** Warn about more ignored function return values.
The compiler now warns when the return value from certain functions is
-ignored. Example:
+implicitly ignored. Example:
(progn (nreverse my-list) my-list)
will elicit a warning because it is usually pointless to call
-'nreverse' on a list without using the returned value. To silence the
-warning, make use of the value in some way, such as assigning it to a
-variable. You can also wrap the function call in '(ignore ...)'.
+'nreverse' on a list without using the returned value.
-This warning can be suppressed using 'with-suppressed-warnings' with
-the warning name 'ignored-return-value'.
+To silence the warning, make use of the value in some way, such as
+assigning it to a variable. You can also wrap the function call in
+'(ignore ...)', or use 'with-suppressed-warnings' with the warning
+name 'ignored-return-value'.
+
+The warning will only be issued for calls to functions declared
+'important-return-value' or 'side-effect-free' (but not 'error-free').
+
++++
+** New function declaration and property 'important-return-value'.
+The declaration '(important-return-value t)' sets the
+'important-return-value' property which indicates that the function
+return value should probably not be thrown away implicitly.
+++
** New function 'file-user-uid'.
(list 'function-put (list 'quote f)
''side-effect-free (list 'quote val))))
+(defalias 'byte-run--set-important-return-value
+ #'(lambda (f _args val)
+ (list 'function-put (list 'quote f)
+ ''important-return-value (list 'quote val))))
+
(put 'compiler-macro 'edebug-declaration-spec
'(&or symbolp ("lambda" &define lambda-list lambda-doc def-body)))
(list 'side-effect-free #'byte-run--set-side-effect-free
"If non-nil, calls can be ignored if their value is unused.
If `error-free', drop calls even if `byte-compile-delete-errors' is nil.")
+ (list 'important-return-value #'byte-run--set-important-return-value
+ "If non-nil, warn about calls not using the returned value.")
(list 'compiler-macro #'byte-run--set-compiler-macro)
(list 'doc-string #'byte-run--set-doc-string)
(list 'indent #'byte-run--set-indent)
;; so maybe we don't need to bother about it here?
(setq form (cons 'progn (cdr form)))
(setq handler #'byte-compile-progn))
- ((and (or sef
- (memq (car form)
- ;; FIXME: Use a function property (declaration)
- ;; instead of this list.
- '(
- ;; Functions that are side-effect-free
- ;; except for the behaviour of
- ;; functions passed as argument.
- mapcar mapcan mapconcat
- cl-mapcar cl-mapcan cl-maplist cl-map cl-mapcon
- cl-reduce
- assoc assoc-default plist-get plist-member
- cl-assoc cl-assoc-if cl-assoc-if-not
- cl-rassoc cl-rassoc-if cl-rassoc-if-not
- cl-member cl-member-if cl-member-if-not
- cl-adjoin
- cl-mismatch cl-search
- cl-find cl-find-if cl-find-if-not
- cl-position cl-position-if cl-position-if-not
- cl-count cl-count-if cl-count-if-not
- cl-remove cl-remove-if cl-remove-if-not
- cl-member cl-member-if cl-member-if-not
- cl-remove-duplicates
- cl-subst cl-subst-if cl-subst-if-not
- cl-substitute cl-substitute-if
- cl-substitute-if-not
- cl-sublis
- cl-union cl-intersection
- cl-set-difference cl-set-exclusive-or
- cl-subsetp
- cl-every cl-some cl-notevery cl-notany
- cl-tree-equal
-
- ;; Functions that mutate and return a list.
- cl-delete-if cl-delete-if-not
- ;; `delete-dups' and `delete-consecutive-dups'
- ;; never delete the first element so it's
- ;; safe to ignore their return value, but
- ;; this isn't the case with
- ;; `cl-delete-duplicates'.
- cl-delete-duplicates
- cl-nsubst cl-nsubst-if cl-nsubst-if-not
- cl-nsubstitute cl-nsubstitute-if
- cl-nsubstitute-if-not
- cl-nunion cl-nintersection
- cl-nset-difference cl-nset-exclusive-or
- cl-nreconc cl-nsublis
- cl-merge
- ;; It's safe to ignore the value of `sort'
- ;; and `nreverse' when used on arrays,
- ;; but most calls pass lists.
- nreverse
- sort cl-sort cl-stable-sort
-
- ;; Adding the following functions yields many
- ;; positives; evaluate how many of them are
- ;; false first.
-
- ;;delq delete cl-delete
- ;;nconc plist-put
- )))
+ ((and (or sef (function-get (car form) 'important-return-value))
;; Don't warn for arguments to `ignore'.
(not (eq byte-compile--for-effect 'for-effect-no-warn))
(byte-compile-warning-enabled-p
(byte-compile-discard))
(pop byte-compile-form-stack)))
+(let ((important-return-value-fns
+ '(
+ ;; These functions are side-effect-free except for the
+ ;; behaviour of functions passed as argument.
+ mapcar mapcan mapconcat
+ assoc plist-get plist-member
+
+ ;; It's safe to ignore the value of `sort' and `nreverse'
+ ;; when used on arrays, but most calls pass lists.
+ nreverse sort
+
+ ;; Adding these functions causes many warnings;
+ ;; evaluate how many of them are false first.
+ ;;delq delete
+ ;;nconc plist-put
+ )))
+ (dolist (fn important-return-value-fns)
+ (put fn 'important-return-value t)))
+
+
(defun byte-compile-normal-call (form)
(when (and (symbolp (car form))
(byte-compile-warning-enabled-p 'callargs (car form)))
'(cl-list* cl-acons cl-equalp
cl-random-state-p copy-tree))
+;;; Things whose return value should probably be used.
+(mapc (lambda (x) (function-put x 'important-return-value t))
+ '(
+ ;; Functions that are side-effect-free except for the
+ ;; behaviour of functions passed as argument.
+ cl-mapcar cl-mapcan cl-maplist cl-map cl-mapcon
+ cl-reduce
+ cl-assoc cl-assoc-if cl-assoc-if-not
+ cl-rassoc cl-rassoc-if cl-rassoc-if-not
+ cl-member cl-member-if cl-member-if-not
+ cl-adjoin
+ cl-mismatch cl-search
+ cl-find cl-find-if cl-find-if-not
+ cl-position cl-position-if cl-position-if-not
+ cl-count cl-count-if cl-count-if-not
+ cl-remove cl-remove-if cl-remove-if-not
+ cl-remove-duplicates
+ cl-subst cl-subst-if cl-subst-if-not
+ cl-substitute cl-substitute-if cl-substitute-if-not
+ cl-sublis
+ cl-union cl-intersection cl-set-difference cl-set-exclusive-or
+ cl-subsetp
+ cl-every cl-some cl-notevery cl-notany
+ cl-tree-equal
+
+ ;; Functions that mutate and return a list.
+ ;;cl-delete
+ cl-delete-if cl-delete-if-not
+ cl-delete-duplicates
+ cl-nsubst cl-nsubst-if cl-nsubst-if-not
+ cl-nsubstitute cl-nsubstitute-if cl-nsubstitute-if-not
+ cl-nunion cl-nintersection cl-nset-difference cl-nset-exclusive-or
+ cl-nreconc cl-nsublis
+ cl-merge
+ ;; It's safe to ignore the value of `cl-sort' and `cl-stable-sort'
+ ;; when used on arrays, but most calls pass lists.
+ cl-sort cl-stable-sort
+ ))
+
+
;;; Types and assertions.
;;;###autoload
If no element matches, the value is nil.
If TEST is omitted or nil, `equal' is used."
+ (declare (important-return-value t))
(let (found (tail alist) value)
(while (and tail (not found))
(let ((elt (car tail)))
projects / emacs.git / commitdiff