std.allocator.allocate(0) -> return null or std.allocator.allocate(1)?

Andrei Alexandrescu via Digitalmars-d digitalmars-d at puremagic.com
Fri May 15 11:51:43 PDT 2015


On 5/15/15 11:37 AM, deadalnix wrote:
> On Friday, 15 May 2015 at 16:36:29 UTC, Andrei Alexandrescu wrote:
>> This is a matter with some history behind it. In C, malloc(0) always
>> returns a new, legit pointer that can be subsequently reallocated,
>> freed etc. What most malloc() implementations practically do in their
>> first line is:
>>
>> if (size == 0) size = 1;
>>
>> and take it from there.
>>
>
> There are actually 2 way to do this in malloc. Either you return null,
> but then you need to be able to accept null in the free implementation
> (as malloc must return a freeable pointer) or you just bump to 1.
>
> Both are valid per spec and there are implementations of malloc for both.

Ah, nice. I was under the misconception that malloc(0) cannot return 
null in C. Apparently it's implementation defined at least since C99, 
see http://stackoverflow.com/a/2132318/348571. Thanks!

Andrei


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