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

[Markus Armbruster <armbru@redhat.com>]

Blue Swirl <blauwirbel@gmail.com> writes:

> 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.

Okay, nothing it is.

>>  By the way, a quick grep shows >50 uses of assert(0).
>
> Not anymore since 43dc2a645e00e6761a741e3d16c27c5b5a373b66.

I doubt the wisdom of such a wholesale conversion, but I it's hardly
worth arguing now.