[Bug c++/58325] New: Spurious unused-but-set-variable warning on delete[] of volatile pointer

[Bug c++/58325] New: Spurious unused-but-set-variable warning on delete[] of volatile pointer

[cyp561 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58325

            Bug ID: 58325
           Summary: Spurious unused-but-set-variable warning on delete[]
                    of volatile pointer
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: cyp561 at gmail dot com

The following code should not generate “volatile.cpp:3:16: warning: variable
‘usedAndSet’ set but not used [-Wunused-but-set-variable]”, but does anyway:

{{{
int main()
{
    int *volatile setAndUsed = new int[1];
    delete[] setAndUsed;
}
}}}

The generated code looks correct, I assume _ZdaPv is the delete[]:

{{{
    .file    "volatile.cpp"
    .section    .text.startup,"ax",@progbits
    .p2align 4,,15
    .globl    main
    .type    main, @function
main:
.LFB0:
    .cfi_startproc
    subq    $24, %rsp
    .cfi_def_cfa_offset 32
    movl    $4, %edi
    call    _Znam
    movq    %rax, 8(%rsp)
    movq    8(%rsp), %rdi
    testq    %rdi, %rdi
    je    .L2
    call    _ZdaPv
.L2:
    xorl    %eax, %eax
    addq    $24, %rsp
    .cfi_def_cfa_offset 8
    ret
    .cfi_endproc
.LFE0:
    .size    main, .-main
    .ident    "GCC: (Gentoo 4.6.4 p1.0, pie-0.5.2) 4.6.4"
    .section    .note.GNU-stack,"",@progbits
}}}

Changing “delete[]” to “delete” or removing “volatile” removes the warning.
Adding “(void)setAndUsed;” squelches the warning.

Gives the warning: g++-4.6.4 g++-4.7.3
Does not give a warning: g++-3.4.6  g++-4.1.2  g++-4.2.4  g++-4.3.6  g++-4.4.7 
g++-4.5.4
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From: "paolo.carlini at oracle dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/58325] Spurious unused-but-set-variable warning on delete[] of volatile pointer
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idX325

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-09-05
                 CC|                            |jakub at gcc dot gnu.org
     Ever confirmed|0                           |1

[Bug c++/58325] [4.7/4.8/4.9 Regression] Spurious unused-but-set-variable warning on delete[] of volatile pointer

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58325

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.7.4
            Summary|Spurious                    |[4.7/4.8/4.9 Regression]
                   |unused-but-set-variable     |Spurious
                   |warning on delete[] of      |unused-but-set-variable
                   |volatile pointer            |warning on delete[] of
                   |                            |volatile pointer

[Bug c++/58325] [4.7/4.8/4.9 Regression] Spurious unused-but-set-variable warning on delete[] of volatile pointer

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58325

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |jakub at gcc dot gnu.org

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 30772
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30772&action=edit
gcc49-pr58325.patch

Untested fix.

[Bug c++/58325] [4.7/4.8/4.9 Regression] Spurious unused-but-set-variable warning on delete[] of volatile pointer

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58325

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Author: jakub
Date: Mon Sep  9 17:12:15 2013
New Revision: 202411

URL: http://gcc.gnu.org/viewcvs?rev=202411&root=gcc&view=rev
Log:
    PR c++/58325
    * init.c (build_vec_delete): Call mark_rvalue_use on base.

    * g++.dg/warn/Wunused-var-21.C: New test.

Added:
    trunk/gcc/testsuite/g++.dg/warn/Wunused-var-21.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/init.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/58325] [4.7/4.8/4.9 Regression] Spurious unused-but-set-variable warning on delete[] of volatile pointer

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58325

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Author: jakub
Date: Mon Sep  9 17:12:50 2013
New Revision: 202412

URL: http://gcc.gnu.org/viewcvs?rev=202412&root=gcc&view=rev
Log:
    PR c++/58325
    * init.c (build_vec_delete): Call mark_rvalue_use on base.

    * g++.dg/warn/Wunused-var-21.C: New test.

Added:
    branches/gcc-4_8-branch/gcc/testsuite/g++.dg/warn/Wunused-var-21.C
Modified:
    branches/gcc-4_8-branch/gcc/cp/ChangeLog
    branches/gcc-4_8-branch/gcc/cp/init.c
    branches/gcc-4_8-branch/gcc/testsuite/ChangeLog

[Bug c++/58325] [4.7 Regression] Spurious unused-but-set-variable warning on delete[] of volatile pointer

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58325

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.7/4.8/4.9 Regression]    |[4.7 Regression] Spurious
                   |Spurious                    |unused-but-set-variable
                   |unused-but-set-variable     |warning on delete[] of
                   |warning on delete[] of      |volatile pointer
                   |volatile pointer            |

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed for 4.8+ so far.

[Bug c++/58325] [4.7 Regression] Spurious unused-but-set-variable warning on delete[] of volatile pointer

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58325

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Author: jakub
Date: Wed May  7 16:03:49 2014
New Revision: 210172

URL: http://gcc.gnu.org/viewcvs?rev=210172&root=gcc&view=rev
Log:
    Backported from mainline
    2013-09-09  Jakub Jelinek  <jakub@redhat.com>

    PR c++/58325
    * init.c (build_vec_delete): Call mark_rvalue_use on base.

    * g++.dg/warn/Wunused-var-21.C: New test.

Added:
    branches/gcc-4_7-branch/gcc/testsuite/g++.dg/warn/Wunused-var-21.C
Modified:
    branches/gcc-4_7-branch/gcc/cp/ChangeLog
    branches/gcc-4_7-branch/gcc/cp/init.c
    branches/gcc-4_7-branch/gcc/testsuite/ChangeLog

[Bug c++/58325] [4.7 Regression] Spurious unused-but-set-variable warning on delete[] of volatile pointer

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58325

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed.