[Bug c++/66543] New: False positive warning "variable set but not used"

[Bug c++/66543] New: False positive warning "variable set but not used"

[ldionne.2 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66543

            Bug ID: 66543
           Summary: False positive warning "variable set but not used"
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ldionne.2 at gmail dot com
  Target Milestone: ---

The following code triggers a "unused but set variable" warning on GCC trunk:

    int main() {
        auto f = []() { };
        [=](auto) {
            using Foo = decltype(f());
        };
    }

I think it is a false positive, since `f` is obviously used.

> g++ --version
g++ (GCC) 6.0.0 20150613 (experimental)

> g++ -std=c++14 worksheet.cpp -fsyntax-only -Wall -Wno-unused-local-typedefs

In function ‘int main()’:
warning: variable ‘f’ set but not used [-Wunused-but-set-variable]
         auto f = []() { };
              ^

Regards,
Louis Dionne
>From gcc-bugs-return-489006-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Mon Jun 15 13:59:47 2015
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Subject: [Bug target/66358] [5/6 Regression] [SH] ICE: in extract_constrain_insn, at recog.c:2232
Date: Mon, 15 Jun 2015 13:59:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf358

--- Comment #12 from Oleg Endo <olegendo at gcc dot gnu.org> ---
(In reply to John Paul Adrian Glaubitz from comment #11)
> Any news on this issue? The sh4 buildds in Debian are currently building a
> snapshot as of 2015-06-13 (r224454), let's see how far it gets.

It will take a while to develop the R0 pre-allocating RTL pass as mentioned in
c#10.  Once this has been done and it's been stabilized it can be backported to
the GCC 5 release branch -- assuming that it will fix the R0 reload problems.

[Bug c++/66543] False positive warning "variable set but not used"

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66543

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-06-18
                 CC|                            |mpolacek at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Confirmed.