public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "jsm28 at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug preprocessor/114007] gcc chokes on __has_cpp_attribute(clang::unsafe_buffer_usage)
Date: Wed, 21 Feb 2024 17:04:54 +0000	[thread overview]
Message-ID: <bug-114007-4-niwf979pUR@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-114007-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114007

--- Comment #16 from Joseph S. Myers <jsm28 at gcc dot gnu.org> ---
I think it's clear that __has_c_attribute(gnu::unused) should only return 1 if
the [[gnu::unused]] syntax is actually parsed. (An unavoidable limitation if it
might return 1 in pre-C23 modes is that if it's used with -pedantic /
-pedantic-errors, such a usage of [[gnu::unused]] would then be diagnosed -
since another principle is that -pedantic / -pedantic-errors should not affect
semantics, in particular not change the return value of __has_c_attribute.)

I also think that __has_c_attribute(gnu::unused) should always parse
successfully in #if, even if it returns 0 in some cases.

It's probably reasonable to accept :: in [[]] attributes in pre-C23 standard
modes where those are two consecutive : tokens (the use of the [[]] syntax at
all would result in a pedwarn-if-pedantic).

Ideally there might be a marker on the tokens as suggested to indicate whether
two such tokens would have been :: if in C23 mode, to avoid accepting other
variants where the two tokens are separated in the sources. (The only reason
it's not valid to produce a single preprocessing token in pre-C23 mode is to
deal with corner cases such as ##-concatenating < :: > where the concatenations
are valid in pre-C23 mode, producing digraphs equivalent to [], but invalid in
C23 mode. Once the preprocessing tokens are converted to tokens, pre-C23
doesn't have any valid cases of two consecutive : tokens.)

  parent reply	other threads:[~2024-02-21 17:04 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-02-20  9:01 [Bug preprocessor/114007] New: " ro at gcc dot gnu.org
2024-02-20  9:02 ` [Bug preprocessor/114007] " ro at gcc dot gnu.org
2024-02-20  9:09 ` iains at gcc dot gnu.org
2024-02-20  9:11 ` ro at CeBiTec dot Uni-Bielefeld.DE
2024-02-20  9:17 ` jakub at gcc dot gnu.org
2024-02-20  9:22 ` jakub at gcc dot gnu.org
2024-02-20  9:29 ` iains at gcc dot gnu.org
2024-02-20  9:31 ` iains at gcc dot gnu.org
2024-02-20  9:35 ` jakub at gcc dot gnu.org
2024-02-20  9:43 ` jakub at gcc dot gnu.org
2024-02-20  9:44 ` jakub at gcc dot gnu.org
2024-02-20 10:01 ` iains at gcc dot gnu.org
2024-02-20 10:12 ` iains at gcc dot gnu.org
2024-02-20 12:04 ` iains at gcc dot gnu.org
2024-02-21 13:58 ` jakub at gcc dot gnu.org
2024-02-21 14:15 ` rsandifo at gcc dot gnu.org
2024-02-21 14:26 ` jakub at gcc dot gnu.org
2024-02-21 17:04 ` jsm28 at gcc dot gnu.org [this message]
2024-02-21 18:29 ` jakub at gcc dot gnu.org
2024-02-22  8:48 ` ro at CeBiTec dot Uni-Bielefeld.DE
2024-02-22  9:45 ` fxcoudert at gmail dot com
2024-02-22  9:45 ` fxcoudert at gmail dot com
2024-02-22  9:50 ` ro at CeBiTec dot Uni-Bielefeld.DE
2024-02-22  9:52 ` iains at gcc dot gnu.org
2024-02-22  9:58 ` ro at CeBiTec dot Uni-Bielefeld.DE
2024-02-22 10:22 ` jakub at gcc dot gnu.org
2024-02-22 10:31 ` ro at CeBiTec dot Uni-Bielefeld.DE
2024-02-22 10:34 ` iains at gcc dot gnu.org
2024-02-22 18:33 ` cvs-commit at gcc dot gnu.org
2024-02-22 18:34 ` jakub at gcc dot gnu.org
2024-03-02  0:39 ` cvs-commit at gcc dot gnu.org
2024-03-04 12:10 ` jakub at gcc dot gnu.org
2024-06-11 10:37 ` cvs-commit at gcc dot gnu.org
2024-06-11 10:50 ` jakub at gcc dot gnu.org

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=bug-114007-4-niwf979pUR@http.gcc.gnu.org/bugzilla/ \
    --to=gcc-bugzilla@gcc.gnu.org \
    --cc=gcc-bugs@gcc.gnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).