On Thu, Dec 05, 2019 at 10:37:33PM +0000, Jonathan Wakely wrote:
> On Thu, 5 Dec 2019 at 22:19, Segher Boessenkool wrote:
> > Or you could write
> >
> > auto __c = (__builtin_memcmp(&*__first1, &*__first2, __len) <=> 0);
> > if (__c)
> > return __c;
> >
> > which is much easier to read, to my eyes anyway. And it is exactly the
> > same for the compiler.
>
> In this case yes, but not in general.
>
> Given:
>
> auto x = foo();
> if (bar(x))
> { }
> some_type y;
>
> The destructor of x won't run until after y has been destroyed. That's
> not at all identical to:
>
> if (auto x = foo(); bar(x))
> { }
> some_type y;
>
> Please don't try to tell me how C++ works :-)
I don't, I wouldn't even *know* that. But this is just the same as in C,
and I do know how to write good C code.
I don't think doing non-trivial things with constructors and destructors
(or anything else!) implicitly is a good idea at all, but that's an
altogether different subject.
Segher
