public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug c/106272] New: clang build: new warning ?
@ 2022-07-12 18:41 dcb314 at hotmail dot com
2022-07-12 19:02 ` [Bug preprocessor/106272] " redi at gcc dot gnu.org
` (8 more replies)
0 siblings, 9 replies; 10+ messages in thread
From: dcb314 at hotmail dot com @ 2022-07-12 18:41 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106272
Bug ID: 106272
Summary: clang build: new warning ?
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: dcb314 at hotmail dot com
Target Milestone: ---
Recent gcc builds with clang say this:
libcpp/include/line-map.h:1882:12: warning: moving a temporary object prevents
copy elision [-Wpessimizing-move]
I have little idea what that means, but the line of code is
return std::move (label_text (buffer, true));
This new warning appears about 700 times, so it might be important.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug preprocessor/106272] clang build: new warning ?
2022-07-12 18:41 [Bug c/106272] New: clang build: new warning ? dcb314 at hotmail dot com
@ 2022-07-12 19:02 ` redi at gcc dot gnu.org
2022-07-12 19:35 ` dcb314 at hotmail dot com
` (7 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: redi at gcc dot gnu.org @ 2022-07-12 19:02 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106272
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2022-07-12
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to David Binderman from comment #0)
> This new warning appears about 700 times, so it might be important.
It's not. But the move is useless and shouldn't be there.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug preprocessor/106272] clang build: new warning ?
2022-07-12 18:41 [Bug c/106272] New: clang build: new warning ? dcb314 at hotmail dot com
2022-07-12 19:02 ` [Bug preprocessor/106272] " redi at gcc dot gnu.org
@ 2022-07-12 19:35 ` dcb314 at hotmail dot com
2022-07-12 20:26 ` egallager at gcc dot gnu.org
` (6 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: dcb314 at hotmail dot com @ 2022-07-12 19:35 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106272
--- Comment #2 from David Binderman <dcb314 at hotmail dot com> ---
I just noticed similar four lines earlier:
libcpp/include/line-map.h:1876:12: warning: moving a temporary object prevents
copy elision [-Wpessimizing-move]
Source code is
return std::move (label_text (const_cast <char *> (buffer), false));
About 700 mentions of this one, as well.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug preprocessor/106272] clang build: new warning ?
2022-07-12 18:41 [Bug c/106272] New: clang build: new warning ? dcb314 at hotmail dot com
2022-07-12 19:02 ` [Bug preprocessor/106272] " redi at gcc dot gnu.org
2022-07-12 19:35 ` dcb314 at hotmail dot com
@ 2022-07-12 20:26 ` egallager at gcc dot gnu.org
2022-07-13 0:09 ` mpolacek at gcc dot gnu.org
` (5 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: egallager at gcc dot gnu.org @ 2022-07-12 20:26 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106272
Eric Gallager <egallager at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |build, diagnostic
CC| |egallager at gcc dot gnu.org
--- Comment #3 from Eric Gallager <egallager at gcc dot gnu.org> ---
Note that GCC has its own version of -Wpessimizing-move, too... any idea why
clang's version of the flag catches it, but gcc's doesn't?
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug preprocessor/106272] clang build: new warning ?
2022-07-12 18:41 [Bug c/106272] New: clang build: new warning ? dcb314 at hotmail dot com
` (2 preceding siblings ...)
2022-07-12 20:26 ` egallager at gcc dot gnu.org
@ 2022-07-13 0:09 ` mpolacek at gcc dot gnu.org
2022-07-13 0:17 ` mpolacek at gcc dot gnu.org
` (4 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2022-07-13 0:09 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106272
Marek Polacek <mpolacek at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |mpolacek at gcc dot gnu.org
--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
(In reply to Eric Gallager from comment #3)
> Note that GCC has its own version of -Wpessimizing-move, too... any idea why
> clang's version of the flag catches it, but gcc's doesn't?
No, but I'm going to reduce libcpp/line-map.ii to create a testcase and file a
bug and since it's my warning, maybe even fix it.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug preprocessor/106272] clang build: new warning ?
2022-07-12 18:41 [Bug c/106272] New: clang build: new warning ? dcb314 at hotmail dot com
` (3 preceding siblings ...)
2022-07-13 0:09 ` mpolacek at gcc dot gnu.org
@ 2022-07-13 0:17 ` mpolacek at gcc dot gnu.org
2022-07-13 0:52 ` mpolacek at gcc dot gnu.org
` (3 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2022-07-13 0:17 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106272
Marek Polacek <mpolacek at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at gcc dot gnu.org |mpolacek at gcc dot gnu.org
Status|NEW |ASSIGNED
--- Comment #5 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
And while at it, why don't I fix this one.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug preprocessor/106272] clang build: new warning ?
2022-07-12 18:41 [Bug c/106272] New: clang build: new warning ? dcb314 at hotmail dot com
` (4 preceding siblings ...)
2022-07-13 0:17 ` mpolacek at gcc dot gnu.org
@ 2022-07-13 0:52 ` mpolacek at gcc dot gnu.org
2022-07-13 18:23 ` cvs-commit at gcc dot gnu.org
` (2 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2022-07-13 0:52 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106272
Marek Polacek <mpolacek at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=106276
--- Comment #6 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
(In reply to Marek Polacek from comment #4)
> (In reply to Eric Gallager from comment #3)
> > Note that GCC has its own version of -Wpessimizing-move, too... any idea why
> > clang's version of the flag catches it, but gcc's doesn't?
>
> No, but I'm going to reduce libcpp/line-map.ii to create a testcase and file
> a bug and since it's my warning, maybe even fix it.
Bug 106276.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug preprocessor/106272] clang build: new warning ?
2022-07-12 18:41 [Bug c/106272] New: clang build: new warning ? dcb314 at hotmail dot com
` (5 preceding siblings ...)
2022-07-13 0:52 ` mpolacek at gcc dot gnu.org
@ 2022-07-13 18:23 ` cvs-commit at gcc dot gnu.org
2022-07-13 18:25 ` mpolacek at gcc dot gnu.org
2022-07-13 19:11 ` dmalcolm at gcc dot gnu.org
8 siblings, 0 replies; 10+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2022-07-13 18:23 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106272
--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:
https://gcc.gnu.org/g:86a15b266a7284f3aa1b12494a475f31416b981d
commit r13-1689-g86a15b266a7284f3aa1b12494a475f31416b981d
Author: Marek Polacek <polacek@redhat.com>
Date: Tue Jul 12 20:18:56 2022 -0400
libcpp: Avoid pessimizing std::move [PR106272]
std::move in a return statement can prevent the NRVO:
<https://developers.redhat.com/blog/2019/04/12/understanding-when-not-to-stdmove-in-c>
PR106272 reports that we have two such cases in class label_text's
member functions. We have -Wpessimizing-move that's supposed to detect
problematic std::move uses, but in this case it didn't trigger. I've filed
PR106276 to track that.
PR preprocessor/106272
libcpp/ChangeLog:
* include/line-map.h (class label_text): Don't std::move in a
return
statement.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug preprocessor/106272] clang build: new warning ?
2022-07-12 18:41 [Bug c/106272] New: clang build: new warning ? dcb314 at hotmail dot com
` (6 preceding siblings ...)
2022-07-13 18:23 ` cvs-commit at gcc dot gnu.org
@ 2022-07-13 18:25 ` mpolacek at gcc dot gnu.org
2022-07-13 19:11 ` dmalcolm at gcc dot gnu.org
8 siblings, 0 replies; 10+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2022-07-13 18:25 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106272
Marek Polacek <mpolacek at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |FIXED
--- Comment #8 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug preprocessor/106272] clang build: new warning ?
2022-07-12 18:41 [Bug c/106272] New: clang build: new warning ? dcb314 at hotmail dot com
` (7 preceding siblings ...)
2022-07-13 18:25 ` mpolacek at gcc dot gnu.org
@ 2022-07-13 19:11 ` dmalcolm at gcc dot gnu.org
8 siblings, 0 replies; 10+ messages in thread
From: dmalcolm at gcc dot gnu.org @ 2022-07-13 19:11 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106272
--- Comment #9 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Thanks!
^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2022-07-13 19:11 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-07-12 18:41 [Bug c/106272] New: clang build: new warning ? dcb314 at hotmail dot com
2022-07-12 19:02 ` [Bug preprocessor/106272] " redi at gcc dot gnu.org
2022-07-12 19:35 ` dcb314 at hotmail dot com
2022-07-12 20:26 ` egallager at gcc dot gnu.org
2022-07-13 0:09 ` mpolacek at gcc dot gnu.org
2022-07-13 0:17 ` mpolacek at gcc dot gnu.org
2022-07-13 0:52 ` mpolacek at gcc dot gnu.org
2022-07-13 18:23 ` cvs-commit at gcc dot gnu.org
2022-07-13 18:25 ` mpolacek at gcc dot gnu.org
2022-07-13 19:11 ` dmalcolm at gcc dot gnu.org
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).