Does 'D' language supports 'C' like VLA?

CraigDillabaugh via Digitalmars-d digitalmars-d at puremagic.com
Mon Apr 13 10:08:56 PDT 2015


On Monday, 13 April 2015 at 17:05:59 UTC, BS & LD wrote:
> On Monday, 13 April 2015 at 17:02:13 UTC, CraigDillabaugh wrote:
>> On Monday, 13 April 2015 at 16:53:55 UTC, BS & LD wrote:
>>> As you know in 'C' you can create a variable-length-array 
>>> using variably modified type and a run-time variable 
>>> allocating a storage for it - the same way for any local 
>>> (normally using the stack).
>>>
>>> However in 'D' I don't see such feature. Code like this fails:
>>>
>>> void main()
>>> {
>>>   size_t szArr = 3;
>>>
>>>   int[szArr] arr;
>>> }
>>>
>>> With this error message:
>>>
>>> error: variable szArr cannot be read at compile time
>>>    int[szArr] arr;
>>>
>>> Life example - 
>>> http://melpon.org/wandbox/permlink/a6CzBhYk88FohKlf
>>>
>>> Note:  I'm also amazed why 'D' compiler can't detect that 
>>> 'szArr' is a constant anyway.
>>
>> This likely belongs in D.learn.  What you are looking for is:
>>
>> int[] arr;
>> arr.length = 3;
>
> I suppose this will allocate the array on the 'heap' or it's 
> storage will last past the function scope doesn't it?
>
> What I want is to allocate such variable-length-array on the 
> stack as any other local variable.

Yes, and as John pointed out it isn't the nicest way to do this. 
Sorry for the noise.


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