[Bug c++/986] g++ misses warning for & on temporary

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

------- Comment #16 from bangerth at dealii dot org  2007-05-08 17:25 -------
(In reply to comment #14)
> Which was wrong, I reported the bug and a guy from MinGW kindly explained that
> if it worked then that would be purely by accident and added:
> " When you declare the argument without '&' then it will make a temporary copy
> of the Automobile object on the stack, but it is wrong to store a reference to
> a temporary object because it will be invalid after the constructor returns.". 

You misunderstand my point: the international C++ standard quite clearly
specifies under what circumstances a program is what it calls "ill-formed"
and when a compiler has to issue an error. Taking the address of a temporary
is completely valid according to this standard (i.e. it conforms to the
*syntax*
of the C++ language), and consequently a compiler can't issue an error.

The fact that the program does something you may not expect, i.e. that the
*semantics* are not what you want, is an entirely different matter. In this
case, the C++ standard says that the behavior of your program is undefined.
Compilers may warn about this, but they may not issue an error.

W.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=986