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* [Bug middle-end/94992] New: gcc thinks a member variable is uninitialised
@ 2020-05-08 5:31 rafael at espindo dot la
2020-05-08 5:57 ` [Bug middle-end/94992] " pinskia at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: rafael at espindo dot la @ 2020-05-08 5:31 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94992
Bug ID: 94992
Summary: gcc thinks a member variable is uninitialised
Product: gcc
Version: 10.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: rafael at espindo dot la
Target Milestone: ---
Created attachment 48477
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48477&action=edit
testcase
In the attached testcase gcc with -O1 (but not -O0 or -O2) produces the
following warning
futures_test.cc:57:22: warning: ‘f2.my_future::_promise’ is used uninitialized
in this function [-Wuninitialized]
57 | : _promise(x._promise)
The produced assembly also uses uninitialized memory.
The problem is that _promise is initialized to nullptr in the default
constructor.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug middle-end/94992] gcc thinks a member variable is uninitialised
2020-05-08 5:31 [Bug middle-end/94992] New: gcc thinks a member variable is uninitialised rafael at espindo dot la
@ 2020-05-08 5:57 ` pinskia at gcc dot gnu.org
2020-05-08 5:58 ` pinskia at gcc dot gnu.org
2020-05-08 15:52 ` rafael at espindo dot la
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2020-05-08 5:57 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94992
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Comment on attachment 48477
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48477
testcase
> my_future f2;
> new (&f2) my_future(std::move(f2));
This is going to be problematic as f2 is being created but you are using the
old object which has the same address as the new one.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug middle-end/94992] gcc thinks a member variable is uninitialised
2020-05-08 5:31 [Bug middle-end/94992] New: gcc thinks a member variable is uninitialised rafael at espindo dot la
2020-05-08 5:57 ` [Bug middle-end/94992] " pinskia at gcc dot gnu.org
@ 2020-05-08 5:58 ` pinskia at gcc dot gnu.org
2020-05-08 15:52 ` rafael at espindo dot la
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2020-05-08 5:58 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94992
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
AS mentioned.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug middle-end/94992] gcc thinks a member variable is uninitialised
2020-05-08 5:31 [Bug middle-end/94992] New: gcc thinks a member variable is uninitialised rafael at espindo dot la
2020-05-08 5:57 ` [Bug middle-end/94992] " pinskia at gcc dot gnu.org
2020-05-08 5:58 ` pinskia at gcc dot gnu.org
@ 2020-05-08 15:52 ` rafael at espindo dot la
2 siblings, 0 replies; 4+ messages in thread
From: rafael at espindo dot la @ 2020-05-08 15:52 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94992
--- Comment #3 from Rafael Avila de Espindola <rafael at espindo dot la> ---
For completeness, this is a reduction of a std::swap(x,x). The placement new
was originally in the move assignment operator.
I was able to reproduce this with gcc 9 by moving a few functions out of line.
As far as I can tell, the relevant standard line is from basic.life:
The lifetime of an object \placeholder{o} of type \tcode{T} ends when:
...
\item the storage which the object occupies is released,
or is reused by an object that is not nested within
\placeholder{o}\iref{intro.object}.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-05-08 15:52 UTC | newest]
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2020-05-08 5:31 [Bug middle-end/94992] New: gcc thinks a member variable is uninitialised rafael at espindo dot la
2020-05-08 5:57 ` [Bug middle-end/94992] " pinskia at gcc dot gnu.org
2020-05-08 5:58 ` pinskia at gcc dot gnu.org
2020-05-08 15:52 ` rafael at espindo dot la
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