[Bug c/64609] New: No -Wbool-compare warning on "(a = 0 && 0) <= 4"

[Bug c/64609] New: No -Wbool-compare warning on "(a = 0 && 0) <= 4"

[chengniansun at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64609

            Bug ID: 64609
           Summary: No -Wbool-compare warning on "(a = 0 && 0) <= 4"
           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

This might not be a bug, but a feature request. There is no -Wbool-compare
warning for the following code. 

$: cat s.c
int a;
void fn1() { ((a = 0 && 0) <= 4); }
$: 
$: gcc-trunk -c s.c -Wbool-compare
$: 
$: clang-trunk -c s.c -Wno-unused-value
s.c:2:28: warning: comparison of constant 4 with boolean expression is always
      true [-Wtautological-constant-out-of-range-compare]
void fn1() { ((a = 0 && 0) <= 4); }
              ~~~~~~~~~~~~ ^  ~
1 warning generated.
$: 
$:

[Bug c/64609] No -Wbool-compare warning on "(a = 0 && 0) <= 4"

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64609

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |49706

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note C the resulting type of a comparison is an integer and not a bool so this
might be causing part of the issue.

This is related to bug 49706 (which I think added -Wbool-compare, I can't keep
track of my own bugs :)).

[Bug c/64609] No -Wbool-compare warning on "(a = 0 && 0) <= 4" and "0 > a < 0"

[chengniansun at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64609

Chengnian Sun <chengniansun at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|No -Wbool-compare warning   |No -Wbool-compare warning
                   |on "(a = 0 && 0) <= 4"      |on "(a = 0 && 0) <= 4" and
                   |                            |"0 > a < 0"

--- Comment #2 from Chengnian Sun <chengniansun at gmail dot com> ---
Another test case. 


$: cat s.c 
int a;
void f() { 
  (0 > a < 0);
}
$: 
$: gcc-trunk -Wbool-compare -Wtype-limits -c s.c
$:

[Bug c/64609] No -Wbool-compare warning on "(a = 0 && 0) <= 4" and "0 > a < 0"

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64609

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-03-17
                 CC|                            |mpolacek at gcc dot gnu.org
     Ever confirmed|0                           |1