[Bug middle-end/39891] Bogus location given for warning, no warning at real location: dereferencing pointer �� does break strict-aliasing rules

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2009-04-25 10:41 -------
Thanks for the short testcase.  I'll try to improve the location information.

The compiler at the point of the warning sees

  D.1756_5 = (struct APSInt &) &Val.Data;
  AdditionalOffset.D.1723 = D.1756_5->D.1723;

and complains about dereferencing D.1756_5 which is of type APSInt * but
the object that is accessed is of type void *.  So yes, this is an alias
violation.

What you probably want to do is sth like

class APValue {
private:
  char Data[sizeof(APSInt)];
public:
  APSInt &getInt() {
    return *(new (Data) APSInt);
  }
};

to be conforming.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |diagnostic
   Last reconfirmed|0000-00-00 00:00:00         |2009-04-25 10:41:02
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39891