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* [Bug c++/102801] New: Incorrect -Wmaybe-uninitialized warning/interation for a std::optional only when a nested struct is also present.
@ 2021-10-17 12:47 calin.culianu at bitcoincashnode dot org
2021-10-17 16:43 ` [Bug c++/102801] Incorrect -Wmaybe-uninitialized warning/interaction " redi at gcc dot gnu.org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: calin.culianu at bitcoincashnode dot org @ 2021-10-17 12:47 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102801
Bug ID: 102801
Summary: Incorrect -Wmaybe-uninitialized warning/interation for
a std::optional only when a nested struct is also
present.
Product: gcc
Version: 11.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: calin.culianu at bitcoincashnode dot org
Target Milestone: ---
Created attachment 51617
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51617&action=edit
Test case where a spurious/incorrect -Wmaybe-uninitialized warning is generated
Hi -- I noticed a regression in GCC 10 and GCC 11 related to `std::optional`.
The attached file, if compiled with `-O2 -Wall -std=c++17 -c` as options, will
warn incorrectly about uninitialized members on both GCC 10 and GCC 11 (I
haven't tried 9 yet but I think 8 & 9 are ok).
Note that the key element in the below code is the nested `struct Shared`. If
that is omitted, no warnings occur.
Attached code warns erroneously (GCC 10 & 11):
g++ -O2 -Wall -std=c++17 -c warn3.cpp
Attached code does not warn (nested struct omitted):
g++ -DNO_WARN -O2 -Wall -std=c++17 -c warn3.cpp
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/102801] Incorrect -Wmaybe-uninitialized warning/interaction for a std::optional only when a nested struct is also present.
2021-10-17 12:47 [Bug c++/102801] New: Incorrect -Wmaybe-uninitialized warning/interation for a std::optional only when a nested struct is also present calin.culianu at bitcoincashnode dot org
@ 2021-10-17 16:43 ` redi at gcc dot gnu.org
2021-10-17 20:33 ` egallager at gcc dot gnu.org
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: redi at gcc dot gnu.org @ 2021-10-17 16:43 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102801
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
7, 8, 9 and 10 all warn:
mozilla_jwakely0/warn3.cpp: In function 'void foo(Q<C2>&, std::vector<C2>&)':
mozilla_jwakely0/warn3.cpp:8:7: warning: '<anonymous>.C::b' may be used
uninitialized in this function [-Wmaybe-uninitialized]
8 | class C {
| ^
11 and trunk warn about that and also:
/home/jwakely/gcc/12/include/c++/12.0.0/bits/shared_ptr_base.h:709:19: warning:
'((const std::__shared_count<__gnu_cxx::_S_atomic>*)((char*)&<unnamed> +
offsetof(C2, C2::c.std::optional<C>::<unnamed>.std::_Optional_base<C, false,
false>::_M_payload.std::_Optional_payload<C, false, false,
false>::<unnamed>.std::_Optional_payload<C, true, false,
false>::<unnamed>.std::_Optional_payload_base<C>::_M_payload)))[2].std::__shared_count<>::_M_pi'
may be used uninitialized [-Wmaybe-uninitialized]
709 | : _M_pi(__r._M_pi)
| ~~~~^~~~~
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/102801] Incorrect -Wmaybe-uninitialized warning/interaction for a std::optional only when a nested struct is also present.
2021-10-17 12:47 [Bug c++/102801] New: Incorrect -Wmaybe-uninitialized warning/interation for a std::optional only when a nested struct is also present calin.culianu at bitcoincashnode dot org
2021-10-17 16:43 ` [Bug c++/102801] Incorrect -Wmaybe-uninitialized warning/interaction " redi at gcc dot gnu.org
@ 2021-10-17 20:33 ` egallager at gcc dot gnu.org
2021-10-17 21:59 ` calin.culianu at bitcoincashnode dot org
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: egallager at gcc dot gnu.org @ 2021-10-17 20:33 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102801
Eric Gallager <egallager at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Blocks| |24639
Keywords| |diagnostic
CC| |egallager at gcc dot gnu.org
--- Comment #2 from Eric Gallager <egallager at gcc dot gnu.org> ---
Is this related to and/or a dup of bug 80635?
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=24639
[Bug 24639] [meta-bug] bug to track all Wuninitialized issues
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/102801] Incorrect -Wmaybe-uninitialized warning/interaction for a std::optional only when a nested struct is also present.
2021-10-17 12:47 [Bug c++/102801] New: Incorrect -Wmaybe-uninitialized warning/interation for a std::optional only when a nested struct is also present calin.culianu at bitcoincashnode dot org
2021-10-17 16:43 ` [Bug c++/102801] Incorrect -Wmaybe-uninitialized warning/interaction " redi at gcc dot gnu.org
2021-10-17 20:33 ` egallager at gcc dot gnu.org
@ 2021-10-17 21:59 ` calin.culianu at bitcoincashnode dot org
2022-09-22 13:18 ` [Bug tree-optimization/102801] " rguenth at gcc dot gnu.org
2022-09-22 13:19 ` cvs-commit at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: calin.culianu at bitcoincashnode dot org @ 2021-10-17 21:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102801
--- Comment #3 from Calin Culianu <calin.culianu at bitcoincashnode dot org> ---
@Eric Gallager : Initially I came across that bug and it looked eerily similar
to this one. I am not a gcc dev, just a user of gcc. No idea.. but yeah looks
like in some situations certainly gcc has trouble with this uninitialized
warning when std::optional enters the picture...
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/102801] Incorrect -Wmaybe-uninitialized warning/interaction for a std::optional only when a nested struct is also present.
2021-10-17 12:47 [Bug c++/102801] New: Incorrect -Wmaybe-uninitialized warning/interation for a std::optional only when a nested struct is also present calin.culianu at bitcoincashnode dot org
` (2 preceding siblings ...)
2021-10-17 21:59 ` calin.culianu at bitcoincashnode dot org
@ 2022-09-22 13:18 ` rguenth at gcc dot gnu.org
2022-09-22 13:19 ` cvs-commit at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu.org @ 2022-09-22 13:18 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102801
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Known to work| |12.2.1, 13.0
Status|UNCONFIRMED |RESOLVED
Resolution|--- |FIXED
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
The testcase no longer warns after GCC 12.2 or on GCC 13 trunk for me. I can
re-confirm diagnostics with GCC 10 and GCC 11. I'm going to add the testcase
and close this bug.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/102801] Incorrect -Wmaybe-uninitialized warning/interaction for a std::optional only when a nested struct is also present.
2021-10-17 12:47 [Bug c++/102801] New: Incorrect -Wmaybe-uninitialized warning/interation for a std::optional only when a nested struct is also present calin.culianu at bitcoincashnode dot org
` (3 preceding siblings ...)
2022-09-22 13:18 ` [Bug tree-optimization/102801] " rguenth at gcc dot gnu.org
@ 2022-09-22 13:19 ` cvs-commit at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2022-09-22 13:19 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102801
--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:
https://gcc.gnu.org/g:44dba051d72587828882cbb31118934a4fb06c1a
commit r13-2776-g44dba051d72587828882cbb31118934a4fb06c1a
Author: Richard Biener <rguenther@suse.de>
Date: Thu Sep 22 15:18:47 2022 +0200
tree-optimization/102801 - testcase for uninit diagnostic
The following testcase is fixed in GCC 12+
PR tree-optimization/102801
gcc/testsuite/
* g++.dg/warn/Wuninitialized-33.C: New testcase.
^ permalink raw reply [flat|nested] 6+ messages in thread
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2021-10-17 12:47 [Bug c++/102801] New: Incorrect -Wmaybe-uninitialized warning/interation for a std::optional only when a nested struct is also present calin.culianu at bitcoincashnode dot org
2021-10-17 16:43 ` [Bug c++/102801] Incorrect -Wmaybe-uninitialized warning/interaction " redi at gcc dot gnu.org
2021-10-17 20:33 ` egallager at gcc dot gnu.org
2021-10-17 21:59 ` calin.culianu at bitcoincashnode dot org
2022-09-22 13:18 ` [Bug tree-optimization/102801] " rguenth at gcc dot gnu.org
2022-09-22 13:19 ` cvs-commit at gcc dot gnu.org
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