Re: [Qemu-devel] [PATCH 5/6] error: Link qemu-img, qemu-nbd, qemu-io with qemu-error.o

[Blue Swirl <blauwirbel@gmail.com>]

On 3/18/10, Markus Armbruster <armbru@redhat.com> wrote:
> Blue Swirl <blauwirbel@gmail.com> writes:
>
>  > On 3/18/10, Markus Armbruster <armbru@redhat.com> wrote:
>  >> Blue Swirl <blauwirbel@gmail.com> writes:
>  >>
>  >>  > On 3/17/10, Markus Armbruster <armbru@redhat.com> wrote:
>  >>  >> Blue Swirl <blauwirbel@gmail.com> writes:
>  >>  >>
>  >>  >>  > On 3/17/10, Markus Armbruster <armbru@redhat.com> wrote:
>  >>
>  >> [...]
>  >>
>  >> >>  >>  +void monitor_set_error(Monitor *mon, QError *qerror)
>  >>  >>  >>  +{
>  >>  >>  >>  +    assert(0);
>  >>  >>  >
>  >>  >>  > Please use abort().
>  >>  >>
>  >>  >>
>  >>  >> Why?
>  >>  >
>  >>  > Because assert(0) does not abort when compiled with -DNDEBUG.
>  >>
>  >>
>  >> Why is that a problem?  And why isn't it a problem for the 300+ other
>  >>  assertions in the code?
>  >
>  > We didn't support -DNDEBUG build until recently. Therefore it's safe
>  > to assume that also on production builds assert(0) was equal to
>  > abort(). If the default for production builds changes to -DNDEBUG, we
>  > want to retain the same abort() behaviour.
>  >
>  > The assertions which perform debugging checks aren't a problem. But
>  > assert(0) clearly isn't a debugging check, if you ever reach this line
>  > of code, it's abort() time.
>
>
> I *know* that this line cannot be reached.  That's why I asserted it
>  cannot be reached.
>
>  If you want "this can't ever happen" assertions to be checked, then you
>  shouldn't define NDEBUG.

If you know for sure that this line can't be reached, why bother with
any code at all?

>  Do you still want me to use abort() here?

abort() or nothing at all, as you wish.

>  By the way, a quick grep shows >50 uses of assert(0).

Not anymore since 43dc2a645e00e6761a741e3d16c27c5b5a373b66.