https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19808
--- Comment #40 from Jason Merrill <jason at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #39)
> so - how do I make X::X used and thus prevail? It looks like it doesn't
> really exist
True, for C++14 and up, "X x{};" does aggregate initialization rather than
calling the constructor. We ought to warn about this at function scope, but we
clear the object first, so it isn't actually uninitialized.
As you found, removing the {} makes it use the constructor.
> OK, doing void foo() { X x; } shows
>
> X::X (struct X * const this)
> {
> _1 = this->x2;
> this->x1 = _1;
> this->x2 = 0;
> }
>
> foo ()
> {
> struct X x;
>
> try
> {
> X::X (&x);
> }
> finally
> {
> x = {CLOBBER};
> }
> }
>
> warning would need inlining of the constructor which only happens after
> the early warning pass, the late one isn't run at -O0 and with optimization
> everything of course vanishes.
I was wondering about a maybe-uninitialized warning for the constructor without
considering where it's called from; even if a particular object is
zero-initialized when we enter the implicit constructor, the constructor
shouldn't rely on that. Basically, warn as if there were a clobber, without
there actually being one.
