[Bug c/63357] New: Warn for P && P and P || P

[Bug c/63357] New: Warn for P && P and P || P

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63357

            Bug ID: 63357
           Summary: Warn for P && P and P || P
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mpolacek at gcc dot gnu.org

We probably should warn about (both C/C++):

int
foo (int a, int b)
{
  if (a && a)
    return 1;
  if (b || b)
    return 2;
  if (!a && !a)
    return 3;
  if (!b || !b)
    return 4;
  return 0;
}

See https://gcc.gnu.org/ml/gcc-patches/2014-09/msg02080.html

I suggest this be called -Wredundant-op.  Better names?

[Bug c/63357] Warn for P && P and P || P

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63357

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

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

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
*** Bug 64250 has been marked as a duplicate of this bug. ***

[Bug c/63357] Warn for P && P and P || P (same expression used multiple times in a condition)

[burnus at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63357

Tobias Burnus <burnus at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Warn for P && P and P || P  |Warn for P && P and P || P
                   |                            |(same expression used
                   |                            |multiple times in a
                   |                            |condition)

--- Comment #3 from Tobias Burnus <burnus at gcc dot gnu.org> ---
Augmented summary to make it better searchable. See also related PR64249.

[Bug c/63357] Warn for P && P and P || P (same expression used multiple times in a condition)

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63357

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |mpolacek at gcc dot gnu.org
   Target Milestone|---                         |6.0

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I have an untested patch.

[Bug c/63357] Warn for P && P and P || P (same expression used multiple times in a condition)

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63357

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Depends on|                            |61534

--- Comment #5 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Patch here
https://gcc.gnu.org/ml/gcc-patches/2015-04/msg01137.html
But it's blocked until we resolve PR61534.

[Bug c/63357] Warn for P && P and P || P (same expression used multiple times in a condition)

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63357

--- Comment #6 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Author: mpolacek
Date: Fri Apr 24 12:10:52 2015
New Revision: 222408

URL: https://gcc.gnu.org/viewcvs?rev=222408&root=gcc&view=rev
Log:
    PR c/63357
    * c-common.c (warn_logical_operator): Warn if the operands have the
    same expressions.

    * doc/invoke.texi: Update description of -Wlogical-op.

    * c-c++-common/Wlogical-op-1.c: New test.

Added:
    trunk/gcc/testsuite/c-c++-common/Wlogical-op-1.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/c-family/ChangeLog
    trunk/gcc/c-family/c-common.c
    trunk/gcc/doc/invoke.texi
    trunk/gcc/testsuite/ChangeLog

[Bug c/63357] Warn for P && P and P || P (same expression used multiple times in a condition)

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63357

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

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

--- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Fixed.

[Bug c/63357] Warn for P && P and P || P (same expression used multiple times in a condition)

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63357

David Binderman <dcb314 at hotmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dcb314 at hotmail dot com

--- Comment #8 from David Binderman <dcb314 at hotmail dot com> ---
This could probably be extended to other operators.

Static analyser cppcheck can be made to say things like:

linux-6.2/drivers/spi/spi-sn-f-ospi.c:614:31: style: Same expression
'SPI_TX_OCTAL' found multiple times in chain of '|' operators.
[duplicateExpression]

Source code is

    ctlr->mode_bits = SPI_TX_DUAL | SPI_TX_QUAD | SPI_TX_OCTAL
        | SPI_RX_DUAL | SPI_RX_QUAD | SPI_TX_OCTAL
        | SPI_MODE_0 | SPI_MODE_1 | SPI_LSB_FIRST;

If |, then probably also &.

[Bug c/63357] Warn for P && P and P || P (same expression used multiple times in a condition)

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63357

--- Comment #9 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to David Binderman from comment #8)
> This could probably be extended to other operators.

Please open a new PR mentioning this one.

[Bug c/63357] Warn for P && P and P || P (same expression used multiple times in a condition)

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63357

--- Comment #10 from David Binderman <dcb314 at hotmail dot com> ---
(In reply to Manuel López-Ibáñez from comment #9)
> Please open a new PR mentioning this one.

Done. See 108926.