From: Daniel Colascione <dancol@dancol.org>
To: Emacs developers <emacs-devel@gnu.org>
Cc: Alan Mackenzie <acm@muc.de>
Subject: cc-mode uniform initialization support
Date: Wed, 19 Aug 2015 11:36:11 -0700 [thread overview]
Message-ID: <55D4CC9B.7020302@dancol.org> (raw)
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Recent versions of C++ support using {} to indicate an initialization
value. For example,
1 int foo{5};
2 int bar = {5};
3 mumble_t mumble{
4 foo,
5 bar
6 };
7 return {mumble, foo}; // Type inferred from function declaration
Working with code written in this style is a nightmare right now because
cc-mode recognizes line 4 as defun-block-intro, leading to line 5 being
indented spuriously, since cc-mode thinks it's a statement continuation.
In reality, the construct starting at line 3 is a brace list, but
there's no syntactic clue to tell us that. (We can, of course, look for
an "=", but an "=" is no longer required for a brace list.)
I don't see a way around needing to use awful heuristics to distinguish
the cases. Does anyone have a better idea? Keep in mind that code like
this is common too:
foo({
abc,
def
});
And plenty of people define macros that accept blocks:
MY_FOREACH {
statement1;
statement2;
}
diff --git a/lisp/progmodes/cc-engine.el b/lisp/progmodes/cc-engine.el
index 06b03a2..84f3ad7 100644
--- a/lisp/progmodes/cc-engine.el
+++ b/lisp/progmodes/cc-engine.el
@@ -8725,6 +8725,34 @@ comment at the start of cc-engine.el for more info."
(save-excursion
(goto-char containing-sexp)
(c-backward-over-enum-header))
+ ;; Detect C++11 uniform initialization. This bit is necessarily
+ ;; heuristic, since there are few syntactic clues to go
+ ;; on. Initializer lists can now stand in for any value at all when
+ ;; the compiler can infer the type to build from the
+ ;; initializer list.
+ (save-excursion
+ (goto-char containing-sexp)
+ (and
+ (eq (char-after) ?\{)
+ (progn (c-backward-sws)
+ (or
+ ;; After a comma means universal initialization
+ (eq (char-before) ?\,)
+ ;; Er, we use GCC statement expressions most often in
+ ;; macros, so if we see ({ outside of one, think of it
+ ;; as uniform initialization.
+ (and (eq (char-before) ?\()
+ (save-excursion
+ (not (c-beginning-of-macro))))
+ ;; foo{} versus foo {. Yuck.
+ (and (not (bobp))
+ (prog1
+ (backward-char)
+ (looking-at "\\(\\w\\|\\s_\\){")
+ (forward-char)))
+ ;; Special case for return {...}
+ (looking-back "\\_<return\\=" (point-at-bol))))
+ containing-sexp))
;; this will pick up array/aggregate init lists, even if they are
nested.
(save-excursion
(let ((class-key
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next reply other threads:[~2015-08-19 18:36 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-19 18:36 Daniel Colascione [this message]
2015-08-20 16:49 ` cc-mode uniform initialization support Alan Mackenzie
2015-08-30 0:54 ` Daniel Colascione
2016-07-04 18:32 ` Alan Mackenzie
2016-07-22 21:09 ` Alan Mackenzie
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