[Bug c/65891] New: -Wlogical-op now warns about logical ‘and’ of equal expressions even when different types/sizeofs are involved

[Bug c/65891] New: -Wlogical-op now warns about logical ‘and’ of equal expressions even when different types/sizeofs are involved

[gerald at pfeifer dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65891

            Bug ID: 65891
           Summary: -Wlogical-op now warns about logical ‘and’ of equal
                    expressions even when different types/sizeofs are
                    involved
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gerald at pfeifer dot com
                CC: polacek at redhat dot com
  Target Milestone: ---

Since 2015-04-21  Marek Polacek  <polacek@redhat.com>

    PR c/63357
    * c-common.c (warn_logical_operator): Warn if the operands have the
    same expressions.

we also diagnose code the following

  typedef int r_fun_t (int);

  r_fun_t * text_funcs[] = {0,0,0};

  int report (unsigned t)
  {
    typedef int s_fun_t (long, char);

    static s_fun_t * GUI_funcs[3];

    return (t < sizeof text_funcs / sizeof text_funcs[0] &&
            t < sizeof GUI_funcs / sizeof GUI_funcs[0]);
  }

with

  input: In function ‘report’:
  input:8:58: warning: logical ‘and’ of equal expressions [-Wlogical-op]
     return (t < sizeof text_funcs / sizeof text_funcs[0] &&
                                                          ^

when these two conditions are about two different types, defined in two
different locations, and the sizes are set differently.
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Subject: [Bug c/65891]=?UTF-8?Q? -Wlogical-op now warns about logical ‘and’ of equal expressions even when different types?=/sizeofs are involved
Date: Sat, 25 Apr 2015 20:23:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ide891

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2015-04-25
                 CC|                            |mpolacek at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org
   Target Milestone|---                         |6.0
     Ever confirmed|0                           |1

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Sorry.  I'll look into that.

[Bug c/65891] -Wlogical-op now warns about logical ‘and’ of equal expressions even when different types/sizeofs are involved

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65891

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

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

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
In the ML I wrote:

I'm afraid there isn't an easy solution to this; the problem is that we fold
sizeof early, so the warning sees

  t < sizeof 4 && t < 4

Thus unassigning for now.

[Bug c/65891] -Wlogical-op now warns about logical ‘and’ of equal expressions even when different types/sizeofs are involved

[ktietz at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65891

Kai Tietz <ktietz at gcc dot gnu.org> changed:

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

--- Comment #3 from Kai Tietz <ktietz at gcc dot gnu.org> ---
For C++ delayed folding this issue won't be warned anymore, as for it sizeof
isn't folded early.

[Bug c/65891] [9/10/11/12 Regression] -Wlogical-op now warns about logical ‘and’ of equal expressions even when different types/sizeofs are involved

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65891

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |5.5.0
      Known to fail|                            |6.1.0
            Summary|-Wlogical-op now warns      |[9/10/11/12 Regression]
                   |about logical ‘and’ of      |-Wlogical-op now warns
                   |equal expressions even when |about logical ‘and’ of
                   |different types/sizeofs are |equal expressions even when
                   |involved                    |different types/sizeofs are
                   |                            |involved
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=63357
   Target Milestone|---                         |9.5

[Bug c/65891] [9/10/11/12 Regression] -Wlogical-op now warns about logical ‘and’ of equal expressions even when different types/sizeofs are involved

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65891

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|unknown                     |11.2.1
           Priority|P3                          |P2

[Bug c/65891] [9/10/11/12 Regression] -Wlogical-op now warns about logical ‘and’ of equal expressions even when different types/sizeofs are involved

[jlegg at feralinteractive dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65891

James Legg <jlegg at feralinteractive dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jlegg at feralinteractive dot com

--- Comment #7 from James Legg <jlegg at feralinteractive dot com> ---
(In reply to Kai Tietz from comment #3)
> For C++ delayed folding this issue won't be warned anymore, as for it sizeof
> isn't folded early.

With -fsanitize=integer-divide-by-zero, the spurious warning is still issued in
C++.

[Bug c/65891] [10/11/12/13 Regression] -Wlogical-op now warns about logical ‘and’ of equal expressions even when different types/sizeofs are involved

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65891

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|9.5                         |10.4

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 9 branch is being closed

[Bug c/65891] [10/11/12/13 Regression] -Wlogical-op now warns about logical ‘and’ of equal expressions even when different types/sizeofs are involved

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65891

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.4                        |10.5

--- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 10.4 is being released, retargeting bugs to GCC 10.5.

[Bug c/65891] [11/12/13/14 Regression] -Wlogical-op now warns about logical ‘and’ of equal expressions even when different types/sizeofs are involved

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65891

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.5                        |11.5

--- Comment #10 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 10 branch is being closed.