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References: <bug-32132-7667@http.gcc.gnu.org/bugzilla/>
Subject: [Bug c++/32132] bogus warning at -O3 ( 'r' may be used uninitialized in this function ).
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From: "pinskia at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
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------- Comment #5 from pinskia at gcc dot gnu dot org  2007-05-28 21:48 -------
The warning is correct you need to check if str had an error after reading the
integer.  This is not a GCC bug.

The IR looks like:
<bb 7>:
  __comp_ctor  (&str, s, 8);
  this.104 = (struct ios_base *) &str.D.25711;
  __s = this.104 + *(int *) (str.D.25711._vptr.basic_istream + -12);
  D.40158 = __s->_M_fmtflags;
  __s->_M_fmtflags = D.40158 & -57 | 16;
  _M_get_num (&str.D.25711, &__lval);

<bb 8>:
  if (((this.104 + *(int *) (str.D.25711._vptr.basic_istream +
-12))->_M_iostate & 5) != 0)
    goto <bb 10>;
  else
    goto <bb 9>;

<bb 9>:
  __lval.107 = __lval;
  r = __lval.107;

<bb 10>:
  __comp_dtor  (&str);
  return r;

Which shows for sure r may be used unitialized.   

Note using libstdc++ does not warn about this because we made >> out of line
only which means you will not see the warning (even though the warning is
correct).


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32132