[Bug c/17896] New: The expression (a>0 & b>0) should give clearer warning message (-Wparentheses)

[Bug c/17896] New: The expression (a>0 & b>0) should give clearer warning message (-Wparentheses)

[trt at acm dot org]

gcc -Wparentheses, for the expression:
 
    a & b == c
 
warns "suggest parentheses around comparison in operand of &".
This is good, but alas the same warning is issued for:
 
    a>0 & b>0
 
Here it does not matter whether & or && are used, the semantics are identical.
(In my experience, 75% of such instances are "harmless" in this way.)
This deserves a clearer warning such as:
 
    suggest && instead of & when joining booleans
 
There is a similar issue with || versus |
And also != versus ^ but that is fairly obscure so I will ignore it.

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           Summary: The expression (a>0 & b>0) should give clearer warning
                    message (-Wparentheses)
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: trt at acm dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17896

[Bug c/17896] The expression (a>0 & b>0) should give clearer warning message (-Wparentheses)

[trt at acm dot org]

------- Additional Comments From trt at acm dot org  2004-10-08 20:00 -------
Created an attachment (id=7310)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=7310&action=view)
proposed patch

I've attached a proposed patch for gcc to issue alternate warnings:
 
    suggest && instead of & when joining booleans
    suggest || instead of | when joining booleans
 
The patched gcc continues to warn (or not) as before, but with different text
when the operands are boolean-valued and without side effects.
I used COMPARISON_CLASS_P (t) as an approximation to "boolean-valued".
truth_value_p (TREE_CODE (t)) would be better but is unavailable.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17896

[Bug c/17896] The expression (a>0 & b>0) should give clearer warning message (-Wparentheses)

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-10-08 20:11 -------
As I have mentioned before patches goto gcc-patches@gcc.gnu.org.

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17896

[Bug c/17896] The expression (a>0 & b>0) should give clearer warning message (-Wparentheses)

[trt at acm dot org]

------- Additional Comments From trt at acm dot org  2004-10-09 21:24 -------
Sorry, will do.  Should bugzilla do this automatically for 'patch' attachments?

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17896

[Bug c/17896] The expression (a>0 & b>0) should give clearer warning message (-Wparentheses)

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-10-11 17:12 -------
Patch here: <http://gcc.gnu.org/ml/gcc-patches/2004-10/msg00918.html>.
Confirmed.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |diagnostic, patch
   Last reconfirmed|0000-00-00 00:00:00         |2004-10-11 17:12:24
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17896