assert(obj) is an atrocity

[Alex Rønne Petersen]

On 09-11-2011 01:19, dsimcha wrote:
> On 11/8/2011 7:05 PM, Timon Gehr wrote:
>> On 11/08/2011 11:35 PM, Alex Rønne Petersen wrote:
>>> Hi,
>>>
>>> As the title suggests, I'm going to be rather blunt about this.
>>> assert(obj) testing the invariant *without* doing a null check is insane
>>> for the following reasons:
>>>
>>> 1) It is not what a user expects. It is *unintuitive*.
>>> 2) assert(!obj) does an is-null check. assert(obj) is a completely
>>> broken opposite of this.
>>> 3) No AssertError is thrown, which is the entire point of the built-in
>>> assert().
>>> 4) The few added instructions for the null check hardly matter in a
>>> *debug* build of all things.
>>>
>>> I don't mind assert(obj) testing the invariant of obj. In fact, that
>>> very much makes sense. But please, please, *please* check the object for
>>> null first.
>>
>> +1.
>
> +1. **AND** in debug mode all pointers should be checked for null.
> Conceptually, I fail to see how a null pointer dereference is different
> from an array bounds error. A null pointer is effectively an array with
> length zero.

I agree on that point. Though right now I'd just be happy to have sane 
asserts.

- Alex