[Bug c/21438] New: Warning about division by zero depends on lexical form

[Bug c/21438] New: Warning about division by zero depends on lexical form

[neil at gcc dot gnu dot org]

GCC is supposed to suppress division by zero warnings when floating point. 
However the warning is based on the lexical form, i.e. the unpromoted type.  I
suggest it should depend on the promoted type.

float f[] = {
 1.0f/0.0f,  // No warning
 1.0f/0      // Warning (and diagnostic is on the wrong line in 3.3 at least)
};

-- 
           Summary: Warning about division by zero depends on lexical form
           Product: gcc
           Version: 3.3.3
            Status: UNCONFIRMED
          Severity: minor
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: neil at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21438

[Bug c/21438] Warning about division by zero depends on lexical form

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-05-07 18:18 -------
Confirmed, it is obvious from looking at the code what was wrong.  The following patch should fix it 
but I don't have time to test it fully:
Index: c-typeck.c
===============================================================
====
RCS file: /cvs/gcc/gcc/gcc/c-typeck.c,v
retrieving revision 1.439
diff -u -p -r1.439 c-typeck.c
--- c-typeck.c	2 May 2005 16:02:19 -0000	1.439
+++ c-typeck.c	7 May 2005 18:17:53 -0000
@@ -7462,7 +7462,8 @@ build_binary_op (enum tree_code code, tr
     case EXACT_DIV_EXPR:
       /* Floating point division by zero is a legitimate way to obtain
 	 infinities and NaNs.  */
-      if (warn_div_by_zero && skip_evaluation == 0 && integer_zerop (op1))
+      if (warn_div_by_zero && skip_evaluation == 0
+          && integer_zerop (op1) && code0 != REAL_TYPE)
 	warning (0, "division by zero");
 
       if ((code0 == INTEGER_TYPE || code0 == REAL_TYPE



-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |diagnostic
   Last reconfirmed|0000-00-00 00:00:00         |2005-05-07 18:18:42
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21438

[Bug c/21438] Warning about division by zero depends on lexical form

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-05-07 18:20 -------
Hmm, I wonder why C++ warns though:
t.c:2: warning: division by zero in '1.0e+0f / 0.'
t.c:3: warning: division by zero in '1.0e+0f / 0'

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |3.2.3 3.3.4 3.4.2 4.0.0
                   |                            |4.1.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21438

[Bug c/21438] Warning about division by zero depends on lexical form

[patchapp at dberlin dot org]

------- Comment #3 from patchapp at dberlin dot org  2007-01-16 00:57 -------
Subject: Bug number PR 21438

A patch for this bug has been added to the patch tracker.
The mailing list url for the patch is
http://gcc.gnu.org/ml/gcc-patches/2007-01/msg01166.html


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21438

[Bug c/21438] Warning about division by zero depends on lexical form

[patchapp at dberlin dot org]

------- Comment #4 from patchapp at dberlin dot org  2007-03-12 01:32 -------
Subject: Bug number PR 21438

A patch for this bug has been added to the patch tracker.
The mailing list url for the patch is
http://gcc.gnu.org/ml/gcc-patches/2007-03/msg00700.html


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21438

[Bug c/21438] Warning about division by zero depends on lexical form

[manu at gcc dot gnu dot org]

------- Comment #5 from manu at gcc dot gnu dot org  2007-03-14 18:37 -------
Subject: Bug 21438

Author: manu
Date: Wed Mar 14 18:37:37 2007
New Revision: 122925

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=122925
Log:
2007-03-14  Manuel Lopez-Ibanez  <manu@gcc.gnu.org>

        PR c/21438
        * c-common.h (warn_for_div_by_zero): Declare.
        * c-common.c (warn_for_div_by_zero): Define.
        * c-typeck.c (build_binary_op): Call warn_for_div_zero instead of
        warning.
cp/
        * typeck.c (build_binary_op): Call warn_for_div_zero instead of
        warning.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/c-common.c
    trunk/gcc/c-common.h
    trunk/gcc/c-typeck.c
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/typeck.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21438

[Bug c/21438] Warning about division by zero depends on lexical form

[manu at gcc dot gnu dot org]

------- Comment #6 from manu at gcc dot gnu dot org  2007-03-14 18:39 -------
This is still not fixed. It needs to be re-examined what the proper fix (if
any) should be.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21438

[Bug c/21438] Warning about division by zero depends on lexical form

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=21438

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |pinskia at gcc dot gnu.org
   Last reconfirmed|2005-12-18 01:45:12         |2021-9-28
      Known to fail|                            |

--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Manuel López-Ibáñez from comment #5)
> Subject: Bug 21438

The only thing this patch did was uniformed the code between the front-ends.

I am going to look into fix this once and for all.
GCC is the only compiler which warns for this case even.