[Bug c++/107140] New: Potential false positive uninitialized variable warning with -Wmaybe-uninitialized

[Bug c++/107140] New: Potential false positive uninitialized variable warning with -Wmaybe-uninitialized

[kip at thevertigo dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107140

            Bug ID: 107140
           Summary: Potential false positive uninitialized variable
                    warning with -Wmaybe-uninitialized
           Product: gcc
           Version: 12.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kip at thevertigo dot com
  Target Milestone: ---

I am aware there have been other related issues that have already been opened.
I am not sure if this adds anything new to the discussion, but I have, with
some effort, managed to isolate a minimal that reproduces the issue.

This code is not meant to be run, but it's merely a heavily butchered minimal
to re-create a "'MaximumPriorityQueue' may be used uninitialized" warning. This
originates in Test.cpp on L71. Here is the code: 

    https://godbolt.org/z/a17Eoc3f3

This only appears to happen with >= -O2. My guess is this may be a result of a
complex interaction with the optimizer and how part of the instantiated
template was inlined.

I note that if I reorder m_LessThanComparison with m_MinMaxHeap in Test.cpp,
the warning is suppressed.

[Bug c++/107140] Potential false positive uninitialized variable warning with -Wmaybe-uninitialized

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107140

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |24639
   Last reconfirmed|                            |2022-10-06
           Keywords|                            |diagnostic
             Status|UNCONFIRMED                 |WAITING
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Can you attach the testcase as a tarfile please?


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=24639
[Bug 24639] [meta-bug] bug to track all Wuninitialized issues

[Bug c++/107140] Potential false positive uninitialized variable warning with -Wmaybe-uninitialized

[kip at thevertigo dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107140

--- Comment #2 from Kip Warner <kip at thevertigo dot com> ---
Created attachment 53673
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53673&action=edit
Minimal

[Bug c++/107140] Potential false positive uninitialized variable warning with -Wmaybe-uninitialized

[kip at thevertigo dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107140

--- Comment #3 from Kip Warner <kip at thevertigo dot com> ---
If you click the Save button in Godbolt's CE, you can download a compressed
archive. I've attached it for you.