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* [Bug c++/105130] New: gcc does not warn about unused return value of last expression of statement expr
@ 2022-04-01 19:55 dani at danielbertalan dot dev
2022-04-01 20:14 ` [Bug c++/105130] " dani at danielbertalan dot dev
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: dani at danielbertalan dot dev @ 2022-04-01 19:55 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105130
Bug ID: 105130
Summary: gcc does not warn about unused return value of last
expression of statement expr
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: dani at danielbertalan dot dev
Target Milestone: ---
Created attachment 52739
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52739&action=edit
Proposed patch
The following code does not cause a warning about the return value of the foo()
function being ignored:
$ cat unused.cc
[[nodiscard]] int foo();
int main() {
({ foo(); });
}
$ g++ -Wunused-value -std=c++20 unused.cc
[no warnings]
The issue seems to be that CLEANUP_POINT_EXPR and STATEMENT_LIST -- which are
what statement expressions are turned into -- are not handled in
convert_to_void() (cp/cvt.cc).
The attached patch resolves the issue, but as a newbie to hacking on gcc, I
can't evaluate if it has any unintended consequences.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/105130] gcc does not warn about unused return value of last expression of statement expr
2022-04-01 19:55 [Bug c++/105130] New: gcc does not warn about unused return value of last expression of statement expr dani at danielbertalan dot dev
@ 2022-04-01 20:14 ` dani at danielbertalan dot dev
2022-04-09 6:37 ` egallager at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: dani at danielbertalan dot dev @ 2022-04-01 20:14 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105130
--- Comment #1 from Daniel Bertalan <dani at danielbertalan dot dev> ---
Created attachment 52740
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52740&action=edit
Proposed patch #2
Actually, my proposed patch was definitely incorrect. It didn't allow me to
circumvent the warning by explicitly casting to void. This new version fixes
that issue.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/105130] gcc does not warn about unused return value of last expression of statement expr
2022-04-01 19:55 [Bug c++/105130] New: gcc does not warn about unused return value of last expression of statement expr dani at danielbertalan dot dev
2022-04-01 20:14 ` [Bug c++/105130] " dani at danielbertalan dot dev
@ 2022-04-09 6:37 ` egallager at gcc dot gnu.org
2022-11-28 18:25 ` pinskia at gcc dot gnu.org
2022-11-28 18:30 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: egallager at gcc dot gnu.org @ 2022-04-09 6:37 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105130
Eric Gallager <egallager at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |egallager at gcc dot gnu.org
--- Comment #2 from Eric Gallager <egallager at gcc dot gnu.org> ---
Please send your patch to the gcc-patches mailing list for review.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/105130] gcc does not warn about unused return value of last expression of statement expr
2022-04-01 19:55 [Bug c++/105130] New: gcc does not warn about unused return value of last expression of statement expr dani at danielbertalan dot dev
2022-04-01 20:14 ` [Bug c++/105130] " dani at danielbertalan dot dev
2022-04-09 6:37 ` egallager at gcc dot gnu.org
@ 2022-11-28 18:25 ` pinskia at gcc dot gnu.org
2022-11-28 18:30 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-11-28 18:25 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105130
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I would have thought this was by design. a statement expression last statement
is "used" there.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/105130] gcc does not warn about unused return value of last expression of statement expr
2022-04-01 19:55 [Bug c++/105130] New: gcc does not warn about unused return value of last expression of statement expr dani at danielbertalan dot dev
` (2 preceding siblings ...)
2022-11-28 18:25 ` pinskia at gcc dot gnu.org
@ 2022-11-28 18:30 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-11-28 18:30 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105130
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=39808
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
PR 39808 is the C version.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-11-28 18:30 UTC | newest]
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2022-04-01 19:55 [Bug c++/105130] New: gcc does not warn about unused return value of last expression of statement expr dani at danielbertalan dot dev
2022-04-01 20:14 ` [Bug c++/105130] " dani at danielbertalan dot dev
2022-04-09 6:37 ` egallager at gcc dot gnu.org
2022-11-28 18:25 ` pinskia at gcc dot gnu.org
2022-11-28 18:30 ` pinskia at gcc dot gnu.org
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