GNU bug report logs - #61144
CC Mode 5.35.2 (C/*l); Incorrect fontification (but different from last time)

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

From: Po Lu <luangruo <at> yahoo.com>
To: bug-gnu-emacs <at> gnu.org
Subject: CC Mode 5.35.2 (C/*l); Incorrect fontification (but different from
 last time)
Date: Sun, 29 Jan 2023 19:00:47 +0800

Package: cc-mode

Emacs  : GNU Emacs 30.0.50 (build 41, x86_64-pc-linux-gnu)
 of 2023-01-29
Package: CC Mode 5.35.2 (C/*l)
Buffer Style: gnu
c-emacs-features: (pps-extended-state col-0-paren posix-char-classes gen-string-delim gen-comment-delim syntax-properties category-properties 1-bit)

Insert the following text in a C Mode buffer:

static sfnt_f26dot6
sfnt_mul_f26dot6 (sfnt_f26dot6 a, sfnt_f26dot6 b)
{
#ifdef INT64_MAX
  return (sfnt_f26dot6) ((int64_t) a * b + (1 << 5) >> 6);
#else
  int negative;
  unsigned short al, bl, ah, bh;
  unsigned int lowlong, midlong, hilong;

  negative = 0;

  /* Compensate for complement and determine if the result will be
     negative.  */

  if (a < 0)
    {
      a = -a;
      negative = 1;
    }

  if (b < 0)
    {
      b = -b;
      negative ^= true;
    }

  /* Load low and high words from A and B.  */
  al = a & 0xffff;
  bl = b & 0xffff;
  ah = a >> 16;
  bh = b >> 16;

  /* Multiply the various bits separately.  */
  midlong = (unsigned int) al * bh;
#endif
}

In ``al * bh'', al is fontified as a type, and bh an identifier.

current state:
==============
(setq
 c-basic-offset 2
 c-comment-only-line-offset '(0 . 0)
 c-indent-comment-alist '((anchored-comment column . 0) (end-block space . 1)
			  (cpp-end-block space . 2))
 c-indent-comments-syntactically-p nil
 c-block-comment-prefix ""
 c-comment-prefix-regexp '((pike-mode . "//+!?\\|\\**") (awk-mode . "#+")
			   (other . "//+\\|\\**"))
 c-doc-comment-style '((java-mode . javadoc) (pike-mode . autodoc)
		       (c-mode . gtkdoc) (c++-mode . gtkdoc))
 c-cleanup-list '(scope-operator)
 c-hanging-braces-alist '((substatement-open before after)
			  (arglist-cont-nonempty))
 c-hanging-colons-alist nil
 c-hanging-semi&comma-criteria '(c-semi&comma-inside-parenlist)
 c-backslash-column 48
 c-backslash-max-column 72
 c-special-indent-hook '(t c-gnu-impose-minimum)
 c-label-minimum-indentation 1
 c-offsets-alist '((inexpr-class . +)
		   (inexpr-statement . +)
		   (lambda-intro-cont . +)
		   (inlambda . 0)
		   (template-args-cont c-lineup-template-args +)
		   (incomposition . +)
		   (inmodule . +)
		   (innamespace . +)
		   (inextern-lang . +)
		   (composition-close . 0)
		   (module-close . 0)
		   (namespace-close . 0)
		   (extern-lang-close . 0)
		   (composition-open . 0)
		   (module-open . 0)
		   (namespace-open . 0)
		   (extern-lang-open . 0)
		   (objc-method-call-cont
		    c-lineup-ObjC-method-call-colons
		    c-lineup-ObjC-method-call
		    +
		    )
		   (objc-method-args-cont . c-lineup-ObjC-method-args)
		   (objc-method-intro . [0])
		   (friend . 0)
		   (cpp-define-intro c-lineup-cpp-define +)
		   (cpp-macro-cont . +)
		   (cpp-macro . [0])
		   (inclass . +)
		   (stream-op . c-lineup-streamop)
		   (arglist-cont-nonempty
		    c-lineup-gcc-asm-reg
		    c-lineup-arglist
		    )
		   (arglist-cont c-lineup-gcc-asm-reg 0)
		   (comment-intro
		    c-lineup-knr-region-comment
		    c-lineup-comment
		    )
		   (catch-clause . 0)
		   (else-clause . 0)
		   (do-while-closure . 0)
		   (access-label . -)
		   (case-label . 0)
		   (substatement . +)
		   (statement-case-intro . +)
		   (statement . 0)
		   (brace-entry-open . 0)
		   (brace-list-entry . 0)
		   (brace-list-close . 0)
		   (block-close . 0)
		   (block-open . 0)
		   (inher-cont . c-lineup-multi-inher)
		   (inher-intro . +)
		   (member-init-cont . c-lineup-multi-inher)
		   (member-init-intro . +)
		   (annotation-var-cont . +)
		   (annotation-top-cont . 0)
		   (topmost-intro . 0)
		   (knr-argdecl . 0)
		   (func-decl-cont . +)
		   (inline-close . 0)
		   (class-close . 0)
		   (class-open . 0)
		   (defun-block-intro . +)
		   (defun-close . 0)
		   (defun-open . 0)
		   (c . c-lineup-C-comments)
		   (string . c-lineup-dont-change)
		   (topmost-intro-cont
		    first
		    c-lineup-topmost-intro-cont
		    c-lineup-gnu-DEFUN-intro-cont
		    )
		   (brace-list-intro
		    first
		    c-lineup-2nd-brace-entry-in-arglist
		    c-lineup-class-decl-init-+
		    +
		    )
		   (brace-list-open . +)
		   (inline-open . 0)
		   (arglist-close . c-lineup-arglist)
		   (arglist-intro . c-lineup-arglist-intro-after-paren)
		   (statement-cont . +)
		   (statement-case-open . +)
		   (label . 0)
		   (substatement-label . 0)
		   (substatement-open . +)
		   (knr-argdecl-intro . 5)
		   (statement-block-intro . +)
		   )
 c-buffer-is-cc-mode 'c-mode
 c-tab-always-indent t
 c-syntactic-indentation t
 c-syntactic-indentation-in-macros t
 c-ignore-auto-fill '(string cpp code)
 c-auto-align-backslashes t
 c-backspace-function 'backward-delete-char-untabify
 c-delete-function 'delete-char
 c-electric-pound-behavior nil
 c-default-style '((java-mode . "java") (awk-mode . "awk") (other . "gnu"))
 c-enable-xemacs-performance-kludge-p nil
 c-old-style-variable-behavior nil
 defun-prompt-regexp nil
 tab-width 8
 comment-column 32
 parse-sexp-ignore-comments t
 parse-sexp-lookup-properties t
 auto-fill-function nil
 comment-multi-line t
 comment-start-skip "\\(?://+\\|/\\*+\\)\\s *"
 fill-prefix nil
 fill-column 70
 paragraph-start "[ 	]*\\(//+\\|\\**\\)[ 	]*$\\|^\f"
 adaptive-fill-mode t
 adaptive-fill-regexp "[ 	]*\\(//+\\|\\**\\)[ 	]*\\([ 	]*\\([-–!|#%;>*·•‣⁃◦]+[ 	]*\\)*\\)"
 )

Message #8 received at 61144 <at> debbugs.gnu.org (full text, mbox):

From: Alan Mackenzie <acm <at> muc.de>
To: Po Lu <luangruo <at> yahoo.com>
Cc: 61144 <at> debbugs.gnu.org
Subject: Re: bug#61144: CC Mode 5.35.2 (C/*l); Incorrect fontification (but
 different from last time)
Date: Mon, 30 Jan 2023 21:53:11 +0000

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

Hello, Po.

On Sun, Jan 29, 2023 at 19:00:47 +0800, Po Lu via CC-Mode-help wrote:
> Package: cc-mode

> Emacs  : GNU Emacs 30.0.50 (build 41, x86_64-pc-linux-gnu)
>  of 2023-01-29
> Package: CC Mode 5.35.2 (C/*l)
> Buffer Style: gnu
> c-emacs-features: (pps-extended-state col-0-paren posix-char-classes gen-string-delim gen-comment-delim syntax-properties category-properties 1-bit)

> Insert the following text in a C Mode buffer:

> static sfnt_f26dot6
> sfnt_mul_f26dot6 (sfnt_f26dot6 a, sfnt_f26dot6 b)
> {
> #ifdef INT64_MAX
>   return (sfnt_f26dot6) ((int64_t) a * b + (1 << 5) >> 6);
> #else
>   int negative;
>   unsigned short al, bl, ah, bh;
>   unsigned int lowlong, midlong, hilong;

>   negative = 0;

>   /* Compensate for complement and determine if the result will be
>      negative.  */

>   if (a < 0)
>     {
>       a = -a;
>       negative = 1;
>     }

>   if (b < 0)
>     {
>       b = -b;
>       negative ^= true;
>     }

>   /* Load low and high words from A and B.  */
>   al = a & 0xffff;
>   bl = b & 0xffff;
>   ah = a >> 16;
>   bh = b >> 16;

>   /* Multiply the various bits separately.  */
>   midlong = (unsigned int) al * bh;
> #endif
> }

> In ``al * bh'', al is fontified as a type, and bh an identifier.

Yes.  foo * bar is a difficult case, since it can either be a
multiplication or a declaration of bar as a pointer to foo.  There is no
reliable way to distinguish these two cases without a full parser.  No
doubt c-ts-mode will do better here.

In another similar case, I have disambiguated these with "whitespace
asymmetry" - If there's WS both before and after the "*" or neither,
it's treated as a multiplication.  Otherwise it's a declaration.

I've extended this heuristic to treat the case in your test file.  Would
you try out the attached patch, please (it applies cleanly to the master
branch).  I would be in favour of putting the patch into the release
branch, but given the patch is ~90 lines long, Eli might object.

Anyhow, please try it out, and let me know what you think about it.
Thanks!

[ .... ]

-- 
Alan Mackenzie (Nuremberg, Germany).

[diff.20230130.diff (text/plain, attachment)]

Message #11 received at 61144 <at> debbugs.gnu.org (full text, mbox):

From: Po Lu <luangruo <at> yahoo.com>
To: Alan Mackenzie <acm <at> muc.de>
Cc: 61144 <at> debbugs.gnu.org
Subject: Re: bug#61144: CC Mode 5.35.2 (C/*l); Incorrect fontification (but
 different from last time)
Date: Tue, 31 Jan 2023 09:23:01 +0800

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

> Hello, Po.
>
> On Sun, Jan 29, 2023 at 19:00:47 +0800, Po Lu via CC-Mode-help wrote:
>> Package: cc-mode
>
>> Emacs  : GNU Emacs 30.0.50 (build 41, x86_64-pc-linux-gnu)
>>  of 2023-01-29
>> Package: CC Mode 5.35.2 (C/*l)
>> Buffer Style: gnu
>> c-emacs-features: (pps-extended-state col-0-paren posix-char-classes gen-string-delim gen-comment-delim syntax-properties category-properties 1-bit)
>
>> Insert the following text in a C Mode buffer:
>
>> static sfnt_f26dot6
>> sfnt_mul_f26dot6 (sfnt_f26dot6 a, sfnt_f26dot6 b)
>> {
>> #ifdef INT64_MAX
>>   return (sfnt_f26dot6) ((int64_t) a * b + (1 << 5) >> 6);
>> #else
>>   int negative;
>>   unsigned short al, bl, ah, bh;
>>   unsigned int lowlong, midlong, hilong;
>
>>   negative = 0;
>
>>   /* Compensate for complement and determine if the result will be
>>      negative.  */
>
>>   if (a < 0)
>>     {
>>       a = -a;
>>       negative = 1;
>>     }
>
>>   if (b < 0)
>>     {
>>       b = -b;
>>       negative ^= true;
>>     }
>
>>   /* Load low and high words from A and B.  */
>>   al = a & 0xffff;
>>   bl = b & 0xffff;
>>   ah = a >> 16;
>>   bh = b >> 16;
>
>>   /* Multiply the various bits separately.  */
>>   midlong = (unsigned int) al * bh;
>> #endif
>> }
>
>> In ``al * bh'', al is fontified as a type, and bh an identifier.
>
> Yes.  foo * bar is a difficult case, since it can either be a
> multiplication or a declaration of bar as a pointer to foo.  There is no
> reliable way to distinguish these two cases without a full parser.  No
> doubt c-ts-mode will do better here.
>
> In another similar case, I have disambiguated these with "whitespace
> asymmetry" - If there's WS both before and after the "*" or neither,
> it's treated as a multiplication.  Otherwise it's a declaration.
>
> I've extended this heuristic to treat the case in your test file.  Would
> you try out the attached patch, please (it applies cleanly to the master
> branch).  I would be in favour of putting the patch into the release
> branch, but given the patch is ~90 lines long, Eli might object.
>
> Anyhow, please try it out, and let me know what you think about it.
> Thanks!
>
> [ .... ]

Thank you, this works here.

Message #16 received at 61144-done <at> debbugs.gnu.org (full text, mbox):

From: Alan Mackenzie <acm <at> muc.de>
To: Po Lu <luangruo <at> yahoo.com>
Cc: 61144-done <at> debbugs.gnu.org
Subject: Re: bug#61144: CC Mode 5.35.2 (C/*l); Incorrect fontification (but
 different from last time)
Date: Fri, 3 Feb 2023 21:01:06 +0000

Hello, Po.

On Tue, Jan 31, 2023 at 09:23:01 +0800, Po Lu wrote:
> Alan Mackenzie <acm <at> muc.de> writes:

> > On Sun, Jan 29, 2023 at 19:00:47 +0800, Po Lu via CC-Mode-help wrote:
> >> Package: cc-mode

> >> Emacs  : GNU Emacs 30.0.50 (build 41, x86_64-pc-linux-gnu)
> >>  of 2023-01-29
> >> Package: CC Mode 5.35.2 (C/*l)
> >> Buffer Style: gnu
> >> c-emacs-features: (pps-extended-state col-0-paren posix-char-classes gen-string-delim gen-comment-delim syntax-properties category-properties 1-bit)

[ .... ]

> > Anyhow, please try it out, and let me know what you think about it.
> > Thanks!

> > [ .... ]

> Thank you, this works here.

Thanks!  I've committed the patch and I'm closing the bug with this post.

-- 
Alan Mackenzie (Nuremberg, Germany).

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