[Bug c/26492] -Wstrict-aliasing=2 warns about explicitly allowed cast to pointer to union.

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=26492

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|i486-linux-gnu              |
             Status|UNCONFIRMED                 |NEW
           Keywords|                            |diagnostic
   Last reconfirmed|                            |2018-09-16
                 CC|                            |manu at gcc dot gnu.org
               Host|i486-linux-gnu              |
     Ever confirmed|0                           |1
              Build|i486-linux-gnu              |

--- Comment #3 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
<source>:13:20: warning: dereferencing type-punned pointer might break
strict-aliasing rules [-Wstrict-aliasing]
  4 |     (((union { type __x__; __typeof__(*(ptr)) __y__;} *)(ptr))->__x__)
    |                                                         ~~~~~
....
 13 |       noalias(usa, &a)[1] = 0;
<source>:4:58: note: in definition of macro 'noalias'
4 |     (((union { type __x__; __typeof__(*(ptr)) __y__;} *)(ptr))->__x__)
  |                                                          ^~~