[Bug c++/61951] New: -wExtra switch produce warning: parameter 'ptr' set but not used [-Wunused-but-set-parameter]

[Bug c++/61951] New: -wExtra switch produce warning: parameter 'ptr' set but not used [-Wunused-but-set-parameter]

[moblaza at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61951

            Bug ID: 61951
           Summary: -wExtra switch produce warning: parameter 'ptr' set
                    but not used [-Wunused-but-set-parameter]
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: moblaza at gmail dot com

Created attachment 33204
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33204&action=edit
program with this code example

Hello! Il write code example with lambda expression, with operator new class
allocation, and g++ produce warning:

D:\workspace\gcc_test1\main.cpp:33:67: warning: parameter 'ptr' set but not
used [-Wunused-but-set-parameter]
                 std::for_each(ref.begin(), ref.end(), [](Base* ptr){

but after allocation, lambda parameter is used also in lambda expression with
for_each algorithm. See attached code.

PS.
My: gcc version 4.8.1 (rev5, Built by MinGW-W64 project)

[Bug c++/61951] -Wextra switch produce warning: parameter 'ptr' set but not used [-Wunused-but-set-parameter]

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61951

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-09-17
                 CC|                            |jakub at redhat dot com
            Summary|-wExtra switch produce      |-Wextra switch produce
                   |warning: parameter 'ptr'    |warning: parameter 'ptr'
                   |set but not used            |set but not used
                   |[-Wunused-but-set-parameter |[-Wunused-but-set-parameter
                   |]                           |]
     Ever confirmed|0                           |1

--- Comment #1 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Maybe Jakub is willing to have a look. Otherwise I may come to it.

[Bug c++/61951] -Wextra switch produce warning: parameter 'ptr' set but not used [-Wunused-but-set-parameter]

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61951

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Is there anything wrong on the warning though?

[](Base* ptr){ ptr = new Deliv(); }

I think ptr here is lambda parameter, does it behave any different from
parameter to any other function?
void foo (Base* ptr) { ptr = new Deliv(); }
warns about parameter 'ptr' set but not used intentionally, so why shouldn't it
we warn about it in the lambda?  Doesn't the lambda just leak memory and not
actually store the pointer anywhere (it stores it into the parameter which is
never used)?

[Bug c++/61951] -Wextra switch produce warning: parameter 'ptr' set but not used [-Wunused-but-set-parameter]

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61951

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |INVALID

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Thanks Jakub. Now that I notice that specific line and you confirmed that the
warning is intentional in the non-lambda case, I believe we can close the bug.