GNU bug report logs - #23610
25.0.94; c++-mode doesn't fontify typename... like typename

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Ivan Andrus <darthandrus <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 25.0.94; c++-mode doesn't fontify typename... like typename
Date: Tue, 24 May 2016 11:01:12 -0600

Starting with emacs -Q, Y is not fontified in the snippet below, whereas
X is.

-Ivan


template <typename X, typename... Y>
class bob {

};


In GNU Emacs 25.0.94.2 (x86_64-apple-darwin15.4.0, NS appkit-1404.46
Version 10.11.4 (Build 15E65))
of 2016-05-22 built on iandrus-osx
Repository revision: ae8352b8219b3d40f70fda8986ae86fbef7322fb
Windowing system distributor 'Apple', version 10.3.1404
Configured using:
'configure --with-ns --with-modules
PKG_CONFIG_PATH=/opt/X11/lib/pkgconfig'

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TOOLKIT_SCROLL_BARS NS MODULES

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Message #8 received at 23610 <at> debbugs.gnu.org (full text, mbox):

From: Alan Mackenzie <acm <at> muc.de>
To: Ivan Andrus <darthandrus <at> gmail.com>
Cc: 23610 <at> debbugs.gnu.org
Subject: Re: bug#23610: 25.0.94;
 c++-mode doesn't fontify typename... like typename
Date: 30 May 2016 12:57:17 -0000

Hello, Ivan.

In article <mailman.202.1464109329.1216.bug-gnu-emacs <at> gnu.org> you wrote:
> Starting with emacs -Q, Y is not fontified in the snippet below, whereas
> X is.

I'm not all that familiar with variadic templates.  In the declaration
below, is the "..." token syntactically part of "typename..." or is
better regarded as part of "... Y"?

I also need to get a feel for what keywords can come before the "...".
Obviously "typename", but what about things like "class"?

Do you know of a good web page where these things are explained
completely and concisely, yet readably?  If so, please tell me!

> -Ivan


> template <typename X, typename... Y>
> class bob {

> };


> In GNU Emacs 25.0.94.2 (x86_64-apple-darwin15.4.0, NS appkit-1404.46
> Version 10.11.4 (Build 15E65))
> of 2016-05-22 built on iandrus-osx
> Repository revision: ae8352b8219b3d40f70fda8986ae86fbef7322fb
> Windowing system distributor 'Apple', version 10.3.1404
> Configured using:
> 'configure --with-ns --with-modules
> PKG_CONFIG_PATH=/opt/X11/lib/pkgconfig'

[ .... ]

-- 
Alan Mackenzie (Nuremberg, Germany).

Message #11 received at 23610 <at> debbugs.gnu.org (full text, mbox):

From: Óscar Fuentes <ofv <at> wanadoo.es>
To: Alan Mackenzie <acm <at> muc.de>
Cc: Ivan Andrus <darthandrus <at> gmail.com>, 23610 <at> debbugs.gnu.org
Subject: Re: bug#23610: 25.0.94;
 c++-mode doesn't fontify typename... like typename
Date: Mon, 30 May 2016 15:49:57 +0200

Hello Alan.

Alan Mackenzie <acm <at> muc.de> writes:

> I'm not all that familiar with variadic templates.  In the declaration
> below, is the "..." token syntactically part of "typename..." or is
> better regarded as part of "... Y"?

Neiter, I'll say.

It is legal to omit the name of the parameter pack (the `Y' in the
example).

> I also need to get a feel for what keywords can come before the "...".
> Obviously "typename", but what about things like "class"?

Yes, `class' and `typename' are interchangeable here. There is also
`sizeof':

template <typename ... Ts> struct Foo {
  void print() {
    printf("Intantiated with %d parameters.\n", sizeof...(Ts));
  }
};

int main() {
  Foo<int, double> foo;
  foo.print();
  return 0;
}


Prints

Intantiated with 2 parameters.


> Do you know of a good web page where these things are explained
> completely and concisely, yet readably?  If so, please tell me!

Try this, which is short and precise:

http://en.cppreference.com/w/cpp/language/parameter_pack

Message #14 received at 23610 <at> debbugs.gnu.org (full text, mbox):

From: Alan Mackenzie <acm <at> muc.de>
To: Óscar Fuentes <ofv <at> wanadoo.es>
Cc: Ivan Andrus <darthandrus <at> gmail.com>, 23610 <at> debbugs.gnu.org
Subject: Re: bug#23610: 25.0.94; c++-mode doesn't fontify typename... like
 typename
Date: Mon, 30 May 2016 15:25:39 +0000

Hello, Óscar.

Thanks for your post!

On Mon, May 30, 2016 at 03:49:57PM +0200, Óscar Fuentes wrote:
> Hello Alan.

> Alan Mackenzie <acm <at> muc.de> writes:

> > I'm not all that familiar with variadic templates.  In the declaration
> > below, is the "..." token syntactically part of "typename..." or is
> > better regarded as part of "... Y"?

> Neither, I'll say.

> It is legal to omit the name of the parameter pack (the `Y' in the
> example).

> > I also need to get a feel for what keywords can come before the "...".
> > Obviously "typename", but what about things like "class"?

> Yes, `class' and `typename' are interchangeable here. There is also
> `sizeof':

I thought there might be something like that.  ;-)

> template <typename ... Ts> struct Foo {
>   void print() {
>     printf("Instantiated with %d parameters.\n", sizeof...(Ts));
>   }
> };

> int main() {
>   Foo<int, double> foo;
>   foo.print();
>   return 0;
> }


> Prints

> Intantiated with 2 parameters.


> > Do you know of a good web page where these things are explained
> > completely and concisely, yet readably?  If so, please tell me!

> Try this, which is short and precise:

> http://en.cppreference.com/w/cpp/language/parameter_pack

That looks like exactly what I need.  Thanks very much!

-- 
Alan Mackenzie (Nuremberg, Germany).

Message #17 received at 23610 <at> debbugs.gnu.org (full text, mbox):

From: Alan Mackenzie <acm <at> muc.de>
To: Ivan Andrus <darthandrus <at> gmail.com>
Cc: 23610 <at> debbugs.gnu.org
Subject: Re: bug#23610: 25.0.94;
 c++-mode doesn't fontify typename... like typename
Date: 19 Jun 2016 21:14:40 -0000

Hello, Ivan.

In article <mailman.202.1464109329.1216.bug-gnu-emacs <at> gnu.org> you wrote:
> Starting with emacs -Q, Y is not fontified in the snippet below, whereas
> X is.

> -Ivan


> template <typename X, typename... Y>
> class bob {

> };

[ .... ]

The following patch is a first attempt to fontify parameter packs.  After
applying it, please be sure either to recompile CC Mode entirely, or
first to compile cc-langs.el (which contains macros), and then all three
of cc-fonts.el, cc-engine.el, and cc-mode.el.

It seems to fontify the "Y" above OK.  I've tried it on a stock example
out of Wikipedia, and that works.  Could you try it out on your code,
please, and let me know how well it works.

Here's the patch:




diff -r f70569e7cf8e cc-engine.el
--- a/cc-engine.el	Sun Jun 19 11:54:55 2016 +0000
+++ b/cc-engine.el	Sun Jun 19 21:05:32 2016 +0000
@@ -6910,6 +6910,9 @@
       (while (cond
 	      ((looking-at c-decl-hangon-key)
 	       (c-forward-keyword-clause 1))
+	      ((looking-at c-pack-key)
+	       (goto-char (match-end 1))
+	       (c-forward-syntactic-ws))
 	      ((and c-opt-cpp-prefix
 		    (looking-at c-noise-macro-with-parens-name-re))
 	       (c-forward-noise-clause))))
diff -r f70569e7cf8e cc-langs.el
--- a/cc-langs.el	Sun Jun 19 11:54:55 2016 +0000
+++ b/cc-langs.el	Sun Jun 19 21:05:32 2016 +0000
@@ -1304,6 +1304,14 @@
 (c-lang-defvar c-stmt-delim-chars-with-comma
   (c-lang-const c-stmt-delim-chars-with-comma))
 
+(c-lang-defconst c-pack-ops
+  "Ops which signal C++11's \"parameter pack\""
+  t nil
+  c++ '("..."))
+(c-lang-defconst c-pack-key
+  t (c-make-keywords-re 'appendable (c-lang-const c-pack-ops)))
+(c-lang-defvar c-pack-key (c-lang-const c-pack-key))
+
 (c-lang-defconst c-auto-ops
   ;; Ops which signal C++11's new auto uses.
   t nil


-- 
Alan Mackenzie (Nuremberg, Germany).

Message #20 received at 23610 <at> debbugs.gnu.org (full text, mbox):

From: Ivan Andrus <darthandrus <at> gmail.com>
To: Alan Mackenzie <acm <at> muc.de>
Cc: 23610 <at> debbugs.gnu.org
Subject: Re: bug#23610: 25.0.94;
 c++-mode doesn't fontify typename... like typename
Date: Wed, 22 Jun 2016 09:22:01 -0600

On Sun, Jun 19, 2016 at 3:14 PM, Alan Mackenzie <acm <at> muc.de> wrote:
> Hello, Ivan.
>
> In article <mailman.202.1464109329.1216.bug-gnu-emacs <at> gnu.org> you wrote:
>> Starting with emacs -Q, Y is not fontified in the snippet below, whereas
>> X is.
>
>> -Ivan
>
>
>> template <typename X, typename... Y>
>> class bob {
>
>> };
>
> [ .... ]
>
> The following patch is a first attempt to fontify parameter packs.  After
> applying it, please be sure either to recompile CC Mode entirely, or
> first to compile cc-langs.el (which contains macros), and then all three
> of cc-fonts.el, cc-engine.el, and cc-mode.el.
>
> It seems to fontify the "Y" above OK.  I've tried it on a stock example
> out of Wikipedia, and that works.  Could you try it out on your code,
> please, and let me know how well it works.

It looks pretty good.  I didn't notice this before, but the following example
from Wikipedia is fontified differently if the ... is removed from before the
`args`.  In that case args is fontified with `font-lock-variable-name-face`.

  template<typename... Args> inline void expand(Args&&... args) {
    pass( some_function(args)... );
  }

FWIW, I've seen similar mis-fontifications before (without ...) and it hasn't
bothered me too much.  I just found a reproducible case, so I guess I'll
open a bug for it.

Thanks for working on this.  The raw string support is awesome!

-Ivan

Message #23 received at 23610 <at> debbugs.gnu.org (full text, mbox):

From: Alan Mackenzie <acm <at> muc.de>
To: Ivan Andrus <darthandrus <at> gmail.com>
Cc: 23610 <at> debbugs.gnu.org
Subject: Re: bug#23610: 25.0.94; c++-mode doesn't fontify typename... like
 typename
Date: Thu, 30 Jun 2016 14:36:36 +0000

Hello, Ivan.

On Wed, Jun 22, 2016 at 09:22:01AM -0600, Ivan Andrus wrote:
> On Sun, Jun 19, 2016 at 3:14 PM, Alan Mackenzie <acm <at> muc.de> wrote:
> > In article <mailman.202.1464109329.1216.bug-gnu-emacs <at> gnu.org> you wrote:
> >> Starting with emacs -Q, Y is not fontified in the snippet below, whereas
> >> X is.

> >> -Ivan


> >> template <typename X, typename... Y>
> >> class bob {

> >> };

> > [ .... ]

> > The following patch is a first attempt to fontify parameter packs.  After
> > applying it, please be sure either to recompile CC Mode entirely, or
> > first to compile cc-langs.el (which contains macros), and then all three
> > of cc-fonts.el, cc-engine.el, and cc-mode.el.

> > It seems to fontify the "Y" above OK.  I've tried it on a stock example
> > out of Wikipedia, and that works.  Could you try it out on your code,
> > please, and let me know how well it works.

> It looks pretty good.  I didn't notice this before, but the following example
> from Wikipedia is fontified differently if the ... is removed from before the
> `args`.  In that case args is fontified with `font-lock-variable-name-face`.

>   template<typename... Args> inline void expand(Args&&... args) {
>     pass( some_function(args)... );
>   }

What is this "&&" operator?  It cannot be a logical and, and doesn't look
like anything to do with a move constructor.  I've tried, and failed, to
find an explanation in http://en.cppreference.com/w/cpp/language.  I
didn't find and explanation in the article "variadic templates" in
wikipedia either.  A pointer to a web page explaining it would be much
appreciated.

I'm tempted to commit the patch as it is at the moment, but feel I ought
to understand this "&&" first.

> FWIW, I've seen similar mis-fontifications before (without ...) and it hasn't
> bothered me too much.  I just found a reproducible case, so I guess I'll
> open a bug for it.

> Thanks for working on this.  The raw string support is awesome!

Thanks!  There've recently been one or two bugs fixed for raw string
support.  The corrections are in the Emacs master branch.

> -Ivan

-- 
Alan Mackenzie (Nuremberg, Germany).

Message #26 received at 23610 <at> debbugs.gnu.org (full text, mbox):

From: John Yates <john <at> yates-sheets.org>
To: Alan Mackenzie <acm <at> muc.de>
Cc: Ivan Andrus <darthandrus <at> gmail.com>, 23610 <at> debbugs.gnu.org
Subject: Re: bug#23610: 25.0.94;
 c++-mode doesn't fontify typename... like typename
Date: Thu, 30 Jun 2016 11:10:13 -0400

[Message part 1 (text/plain, inline)]

On Thu, Jun 30, 2016 at 10:36 AM, Alan Mackenzie <acm <at> muc.de> wrote:

> What is this "&&" operator?


​It is an "rvalue reference".

/john​



-- 
John Yates
109 Chandler St, #1
Boston, MA 02116

[Message part 2 (text/html, inline)]

Message #29 received at 23610 <at> debbugs.gnu.org (full text, mbox):

From: Alan Mackenzie <acm <at> muc.de>
To: John Yates <john <at> yates-sheets.org>
Cc: Ivan Andrus <darthandrus <at> gmail.com>, 23610 <at> debbugs.gnu.org
Subject: Re: bug#23610: 25.0.94; c++-mode doesn't fontify typename... like
 typename
Date: Thu, 30 Jun 2016 16:47:10 +0000

Hello, John.

On Thu, Jun 30, 2016 at 11:10:13AM -0400, John Yates wrote:
> On Thu, Jun 30, 2016 at 10:36 AM, Alan Mackenzie <acm <at> muc.de> wrote:

> > What is this "&&" operator?


> It is an "rvalue reference".

Thanks, that's exactly what I needed to know.  I've now got these
"Args&&... args" expressions fontifying.

> /john



> -- 
> John Yates
> 109 Chandler St, #1
> Boston, MA 02116

-- 
Alan Mackenzie (Nuremberg, Germany).

Message #32 received at 23610 <at> debbugs.gnu.org (full text, mbox):

From: Alan Mackenzie <acm <at> muc.de>
To: Ivan Andrus <darthandrus <at> gmail.com>
Cc: 23610 <at> debbugs.gnu.org
Subject: Re: bug#23610: 25.0.94; c++-mode doesn't fontify typename... like
 typename
Date: Thu, 30 Jun 2016 17:24:32 +0000

Hello again, Ivan.

On Wed, Jun 22, 2016 at 09:22:01AM -0600, Ivan Andrus wrote:
> On Sun, Jun 19, 2016 at 3:14 PM, Alan Mackenzie <acm <at> muc.de> wrote:
> > Hello, Ivan.

> > In article <mailman.202.1464109329.1216.bug-gnu-emacs <at> gnu.org> you wrote:
> >> Starting with emacs -Q, Y is not fontified in the snippet below, whereas
> >> X is.

> >> -Ivan


> >> template <typename X, typename... Y>
> >> class bob {

> >> };

> > [ .... ]

> > The following patch is a first attempt to fontify parameter packs.  After
> > applying it, please be sure either to recompile CC Mode entirely, or
> > first to compile cc-langs.el (which contains macros), and then all three
> > of cc-fonts.el, cc-engine.el, and cc-mode.el.

> > It seems to fontify the "Y" above OK.  I've tried it on a stock example
> > out of Wikipedia, and that works.  Could you try it out on your code,
> > please, and let me know how well it works.

> It looks pretty good.  I didn't notice this before, but the following example
> from Wikipedia is fontified differently if the ... is removed from before the
> `args`.  In that case args is fontified with `font-lock-variable-name-face`.

>   template<typename... Args> inline void expand(Args&&... args) {
>     pass( some_function(args)... );
>   }

OK.  I think the patch below fixes it.  Please try it out and report
back.  (Same instructions about recompilation of CC Mode as last time
apply, since further macros in cc-langs.el have been modified).  Please
note that the patch below is complete in itself, it isn't incremental,
based on the last patch.  It's based on a current Emacs master branch.




diff --git a/lisp/progmodes/cc-engine.el b/lisp/progmodes/cc-engine.el
index 48b9e5e..cc60175 100644
--- a/lisp/progmodes/cc-engine.el
+++ b/lisp/progmodes/cc-engine.el
@@ -7090,6 +7090,9 @@ c-forward-type
       (while (cond
 	      ((looking-at c-decl-hangon-key)
 	       (c-forward-keyword-clause 1))
+	      ((looking-at c-pack-key)
+	       (goto-char (match-end 1))
+	       (c-forward-syntactic-ws))
 	      ((and c-opt-cpp-prefix
 		    (looking-at c-noise-macro-with-parens-name-re))
 	       (c-forward-noise-clause))))
diff --git a/lisp/progmodes/cc-langs.el b/lisp/progmodes/cc-langs.el
index 4d36684..b903190 100644
--- a/lisp/progmodes/cc-langs.el
+++ b/lisp/progmodes/cc-langs.el
@@ -1329,6 +1329,14 @@ 'c-opt-op-identitier-prefix
 (c-lang-defvar c-stmt-delim-chars-with-comma
   (c-lang-const c-stmt-delim-chars-with-comma))
 
+(c-lang-defconst c-pack-ops
+  "Ops which signal C++11's \"parameter pack\""
+  t nil
+  c++ '("..."))
+(c-lang-defconst c-pack-key
+  t (c-make-keywords-re 'appendable (c-lang-const c-pack-ops)))
+(c-lang-defvar c-pack-key (c-lang-const c-pack-key))
+
 (c-lang-defconst c-auto-ops
   ;; Ops which signal C++11's new auto uses.
   t nil
@@ -2958,6 +2966,10 @@ 'c-opt-op-identitier-prefix
 		   "\\)"
 		   "\\([^=]\\|$\\)")
   c++  (concat "\\("
+	       "&&"
+	       "\\|"
+	       "\\.\\.\\."
+	       "\\|"
 	       "[*(&]"
 	       "\\|"
 	       (c-lang-const c-type-decl-prefix-key)


> -Ivan

-- 
Alan Mackenzie (Nuremberg, Germany).

Message #37 received at 23610-done <at> debbugs.gnu.org (full text, mbox):

From: Alan Mackenzie <acm <at> muc.de>
To: 23610-done <at> debbugs.gnu.org
Cc: Ivan Andrus <darthandrus <at> gmail.com>
Subject: Re: bug#23610: 25.0.94; c++-mode doesn't fontify typename... like
 typename
Date: Sat, 23 Jul 2016 15:13:14 +0000

Bug fixed in master.

-- 
Alan Mackenzie (Nuremberg, Germany).

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