[Bug c++/34198] -Wconversion gives apparent erroneous warning with g++ 4.3-20071109

["jakub at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #5 from jakub at gcc dot gnu dot org  2007-11-22 23:04 -------
See the shorten code in e.g. c-typeck.c's build_binary_op.
I think there are two possible fixes:
1) if shortening (i.e. final_type != result_type) don't convert_and_check
to result_type, but instead convert to result_type, and
warnings_for_convert_and_check to final_type
2) in conversion_warning's != REAL_CST != INTEGER_CST
   TREE_CODE (TREE_TYPE (expr)) == INTEGER_TYPE
   && TREE_CODE (type) == INTEGER_TYPE case use get_narrower to see if
   expr is zero or sign extended some smaller type.
   If say type is unsigned char and expr is (int) b where unsigned char b;
   then we shouldn't really warn, the conversions together can't alter
   its value, nor change sign etc.
I think 2) is strongly preferrable.
Will try a patch tomorrow^H^H^H^H^H^H^H^Htoday.


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |jakub at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2007-11-22 22:43:19         |2007-11-22 23:04:36
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34198