assert(obj) is an atrocity

[Timon Gehr]

On 11/09/2011 04:52 AM, bcs wrote:
> On 11/08/2011 04:28 PM, Timon Gehr wrote:
>> On 11/09/2011 01:21 AM, Timon Gehr wrote:
>>> On 11/09/2011 01:18 AM, Martin Nowak wrote:
>>>> On Tue, 08 Nov 2011 23:35:33 +0100, Alex Rønne Petersen
>>>> <xtzgzorex at gmail.com> 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. This is a random inconsistency in the language with no
>>>>> other justification than "seg faults are convenient in a debugger". By
>>>>> the same logic, we might as well not have array bounds checks.
>>>>> However, the state of things is that array bounds checks are emitted
>>>>> by default and users can disable them for e.g. a release build. I
>>>>> don't see why this case is any different.
>>>>>
>>>>> - Alex
>>>>
>>>> It does check for null.
>>>> Only it's a runtime support function (_d_invariant) and druntime is
>>>> likely
>>>> compiled without assertions. Are you really suggesting to add a null
>>>> check before
>>>> every method call?
>>>>
>>>> martin
>>>
>>> No, he is suggesting to add a null check for assert(objref);, a
>>> construct that *looks* as if it was a null check, but does something
>>> almost unrelated.
>>
>> BTW, the number of occurrences of assert(objref && 1); in my code is
>> huge.
>>
>
> I would have used assert(!!obj) because it's shorter.
>

If you have already typed 'assert(obj', it is not shorter.