[Bug c/64610] New: No -Wbool-compare warning on "(0 != a) >= 0"

[Bug c/64610] New: No -Wbool-compare warning on "(0 != a) >= 0"

[chengniansun at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64610

            Bug ID: 64610
           Summary: No -Wbool-compare warning on "(0 != a) >= 0"
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: chengniansun at gmail dot com

There is no warning on the expression "(0 != a) >= 0". I think the cause of
this bug is different from the one I reported just now (PR64609). 


$: cat s.c
int a;
void fn1() { ((0 != a) >= 0); }
$: 
$: gcc-trunk -Wbool-compare -c s.c
$: 
$: clang-trunk -Wno-unused-value -c s.c
s.c:2:24: warning: comparison of constant 0 with boolean expression is always
      true [-Wtautological-constant-out-of-range-compare]
void fn1() { ((0 != a) >= 0); }
              ~~~~~~~~ ^  ~
1 warning generated.
$: 
$:

[Bug c/64610] No -Wbool-compare warning on "(0 != a) >= 0"

[chengniansun at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64610

--- Comment #1 from Chengnian Sun <chengniansun at gmail dot com> ---
I have another test case, for which either -Wtype-limits or -Wbool-compare does
not warn. 

$: cat s.c
void f(int b) {
  (b == 1) >= 0UL;
}
$: 
$: gcc-trunk -Wtype-limits -Wbool-compare -c s.c
$:

[Bug c/64610] No -Wbool-compare warning on "(0 != a) >= 0"

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64610

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

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

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Thanks for your report.  I'll look at enhancing this warning in the GCC 6
stage1.

[Bug c/64610] No -Wbool-compare warning on "(0 != a) >= 0"

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64610

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-03-17
     Ever confirmed|0                           |1

[Bug c/64610] No -Wbool-compare warning on "(0 != a) >= 0"

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64610

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

[Bug c/64610] No -Wbool-compare warning on "(0 != a) >= 0"

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64610

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Author: mpolacek
Date: Wed Apr 29 18:13:44 2015
New Revision: 222587

URL: https://gcc.gnu.org/viewcvs?rev=222587&root=gcc&view=rev
Log:
        PR c/64610
        * c-common.c (maybe_warn_bool_compare): Warn when comparing a boolean
        with 0/1.

        * c-c++-common/Wbool-compare-1.c (fn1): Remove a few lines.
        * c-c++-common/Wbool-compare-2.c: New test.

Added:
    trunk/gcc/testsuite/c-c++-common/Wbool-compare-2.c
Modified:
    trunk/gcc/c-family/ChangeLog
    trunk/gcc/c-family/c-common.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/c-c++-common/Wbool-compare-1.c

[Bug c/64610] No -Wbool-compare warning on "(0 != a) >= 0"

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64610

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

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

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Should be fixed.