From: Helmut Zeisel <HZ2012@gmx.at>
To: Jonathan Wakely <jwakely.gcc@gmail.com>, gcc@gcc.gnu.org
Subject: Aw: Re: Warning: shared mutable data
Date: Fri, 17 Feb 2023 16:57:08 +0100 [thread overview]
Message-ID: <trinity-3fcba8f2-a1a7-495f-9999-a098e90fd890-1676649428481@3c-app-gmx-bap61> (raw)
In-Reply-To: <CAH6eHdQP4CHPcsfLT1=szPMvrdNrUqiDzVskXyHi0RCo-bJtJw@mail.gmail.com>
Von: "Jonathan Wakely" <jwakely.gcc@gmail.com>
> What exactly are you suggesting for the semantics of the warning?
Good question. It is difficult to detect all suspiscious cases, but at least some of the can be defined:
If we have a function prototype
f(...,Ti xi,...Tj xj,...)
and call the function f(... xi, ... xj,...) with some xi, xj with aliasing / data sharing,
and both Ti and Tj are references/pointers and at least one is a non-const pointer / reference,
then the warning should be given.
E.g. for both int:
Ti int: no warning
Ti int& or int*: warning if Tj is int*, const int*, int&, or const int&; no warning for Tj int.
Ti const int& or const int*: warning if Tj is int*, or int&; no warning if Tj is const int*, const int&, or int.
Or maybe some code example:
void increase_x_by_y_and_z(int& x, const int& y, const int& z)
{
x+=y;
x+=z;
}
This should be OK (no sharing, no warning):
x=1;
y=1;
z=1;
increase_x_by_y_and_z(x,y,z);
This should give a warning (sharing of int& and const int&):
x=1;
y=1;
increase_x_by_y_and_z(x,y,x);
On the other hand, this is OK (y is shared but not mutable - two times const int&):
x=1;
y=1;
increase_x_by_y_and_z(x,y,y);
Helmut
prev parent reply other threads:[~2023-02-17 15:57 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-17 13:14 Helmut Zeisel
2023-02-17 14:06 ` Jonathan Wakely
2023-02-17 15:57 ` Helmut Zeisel [this message]
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=trinity-3fcba8f2-a1a7-495f-9999-a098e90fd890-1676649428481@3c-app-gmx-bap61 \
--to=hz2012@gmx.at \
--cc=gcc@gcc.gnu.org \
--cc=jwakely.gcc@gmail.com \
/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).