public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/97548] New: bogus -Wvla-parameter on a bound expression involving a parameter
Date: Fri, 23 Oct 2020 15:14:04 +0000 [thread overview]
Message-ID: <bug-97548-4@http.gcc.gnu.org/bugzilla/> (raw)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97548
Bug ID: 97548
Summary: bogus -Wvla-parameter on a bound expression involving
a parameter
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
>From https://gcc.gnu.org/pipermail/gcc/2020-October/234036.html:
The warning on the redeclaration of g() is a false positive.
$ cat a.c && gcc -S -Wall a.c
int n;
void f (int, int [n + 1]);
void f (int, int [n + 1]); // ok
void g (int k, int [k + 1]);
void g (int k, int [k + 1]); // bogus warning
a.c:7:16: warning: argument 2 of type ‘int[k + 1]’ declared with mismatched
bound ‘k + 1’ [-Wvla-parameter]
7 | void g (int k, int [k + 1]); // bogus warning
| ^~~~~~~~~~~
a.c:6:16: note: previously declared as ‘int[k + 1]’ with bound ‘k + 1’
6 | void g (int k, int [k + 1]);
| ^~~~~~~~~~~
The warning code relies on operand_equal_p() to match the bounds. The function
fails to match the bound expressions because the PARM_DECL referenced in each
is distinct. The code in operand_compare::operand_equal_p() that fails to
match them is:
case tcc_declaration:
/* Consider __builtin_sqrt equal to sqrt. */
return (TREE_CODE (arg0) == FUNCTION_DECL
&& fndecl_built_in_p (arg0) && fndecl_built_in_p (arg1)
&& DECL_BUILT_IN_CLASS (arg0) == DECL_BUILT_IN_CLASS (arg1)
&& (DECL_UNCHECKED_FUNCTION_CODE (arg0)
== DECL_UNCHECKED_FUNCTION_CODE (arg1)));
The matching between two expressions will never be perfect but it should work
for the basic cases.
next reply other threads:[~2020-10-23 15:14 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-23 15:14 msebor at gcc dot gnu.org [this message]
2020-11-24 0:33 ` [Bug c/97548] " msebor at gcc dot gnu.org
2021-01-05 15:51 ` muecker at gwdg dot de
2021-07-02 1:03 ` msebor at gcc dot gnu.org
2021-07-15 16:23 ` cvs-commit at gcc dot gnu.org
2021-07-15 16:25 ` msebor at gcc dot gnu.org
2021-07-23 19:16 ` [Bug c/97548] [11 Regression] " msebor at gcc dot gnu.org
2021-07-23 19:41 ` msebor at gcc dot gnu.org
2021-07-28 7:05 ` rguenth at gcc dot gnu.org
2021-12-16 22:47 ` cvs-commit at gcc dot gnu.org
2022-03-17 19:45 ` msebor 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-97548-4@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).