Package: cc-mode;
Reported by: Arsen Arsenović <arsen <at> aarsen.me>
Date: Wed, 18 Sep 2024 23:49:01 UTC
Severity: normal
Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):
From: Arsen Arsenović <arsen <at> aarsen.me> To: bug-gnu-emacs <at> gnu.org Subject: CC Mode 5.35.2 (C++//l); inline-open lacks associated position, making it hard to express the libstdc++ indent style Date: Thu, 19 Sep 2024 01:48:01 +0200
Package: cc-mode
Hi!
In the following snippet, which is intentionally misindented on the
template line:
struct s
{
template<typename>
void
f()
{}
};
CC-mode seems to not be able to deduce that {} should line up with f().
This is troublesome in a real mode example of libstdc++, whose code
style mandates that templates receive an extra level of indentation:
template<>
void
f()
{
// this is OK
}
struct s
{
template<>
void
f()
{
// this is not OK
}
};
Now, this style required some special handling so far, of course:
--8<---------------cut here---------------start------------->8---
(defun glibcxx/lineup-template-cont (sym-form)
"Indents sym-forms with a single level if they are a continuation of a
template. Implements rules 4 and 5 (Template class indentation,
Template function indentation)."
(save-excursion
(goto-char (c-langelem-pos sym-form))
(if (looking-at-p "\\<template\\>")
'+
nil)))
(defun glibcxx/2nd-col ()
"Returns the second positions column from the current `c-langelem-sym'."
(save-excursion
(let ((pos (c-langelem-2nd-pos c-syntactic-element)))
(if (not pos)
nil
(goto-char pos)
(current-column)))))
(defun glibcxx/lineup-class-open-close (sym-form)
"Indents class-open/class-close lines with their corresponding class/struct
lines."
(if (not (seq-contains-p '(class-open class-close)
(c-langelem-sym sym-form)))
nil
(let ((col (glibcxx/2nd-col)))
(if col
(vector col)
nil))))
(defconst glibcxx/cc-style
'("gnu"
(c-offsets-alist . ((topmost-intro-cont
. (first glibcxx/lineup-template-cont
c-lineup-topmost-intro-cont
c-lineup-gnu-DEFUN-intro-cont))
(defun-open . glibcxx/lineup-template-cont)
(class-open . glibcxx/lineup-class-open-close)
(class-close . glibcxx/lineup-class-open-close)
;; 07. Member initialization lists
(member-init-intro . 0))))
"Code style used by the GNU C++ Standard Library")
--8<---------------cut here---------------end--------------->8---
... but the trouble arose when I went to add the same styling to inline
functions, since inline-open does not have a position relative to the
template; for s::f above, syntactic analysis gives us: ((inclass 61)
(inline-open)). As a result, the definition must be relative to the
class definition itself, but it is not in the case of member templates.
The full libstdc++ code style is presented here:
https://gcc.gnu.org/onlinedocs/libstdc++/manual/source_code_style.html
I'd also like to ask if you'd like to have it in-tree (I'd be happy to
work on it). Really, the code style is a bit strange IMO, but it is
what it is.
Thank you in advance, and sorry to bother you again so soon :-/
Have a lovely day.
Emacs : GNU Emacs 31.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.42, cairo version 1.18.0)
of 2024-08-31
Package: CC Mode 5.35.2 (C++//l)
Buffer Style: glibcxx
c-emacs-features: (pps-extended-state col-0-paren posix-char-classes gen-string-delim gen-comment-delim syntax-properties category-properties 1-bit)
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
c-lineup-template-args-indented-from-margin)
(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 . 0)
(annotation-var-cont . +)
(annotation-top-cont . 0)
(constraint-cont . +)
(topmost-intro . 0)
(knr-argdecl . 0)
(func-decl-cont . +)
(inline-close . 0)
(class-close . glibcxx/lineup-class-open-close)
(class-open . glibcxx/lineup-class-open-close)
(defun-block-intro . +)
(defun-close . 0)
(defun-open . glibcxx/lineup-template-cont)
(c . c-lineup-C-comments)
(string . c-lineup-dont-change)
(topmost-intro-cont first glibcxx/lineup-template-cont
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 'c-do-auto-fill
comment-multi-line t
comment-start-skip "\\(?://+\\|/\\*+\\)\\s *"
fill-prefix nil
fill-column 79
paragraph-start "[ ]*\\(//+\\|\\**\\)[ ]*$\\|^\f"
adaptive-fill-mode t
adaptive-fill-regexp "[ ]*\\(//+\\|\\**\\)[ ]*\\([-–!|#%;>*·•‣⁃◦ ]*\\)"
)
--
Arsen Arsenović
GNU bug tracking system
Copyright (C) 1999 Darren O. Benham,
1997,2003 nCipher Corporation Ltd,
1994-97 Ian Jackson.