static array crashes my program

Steven Schveighoffer via Digitalmars-d-learn digitalmars-d-learn at puremagic.com
Sat Dec 5 06:19:49 PST 2015


On 12/5/15 8:09 AM, John Colvin wrote:
> On Saturday, 5 December 2015 at 09:49:06 UTC, ref2401 wrote:
>> I want to create a static array large enough to store 1MB of float
>> values.
>> What am I doing wrong?
>> Here is a sample code with notes:
>>
>> void main(string[] args) {
>>     enum size_t COUNT = 1024 * 512 / float.sizeof; // works OK :)
>>     //enum size_t COUNT = 1024 * 512 * 2 / float.sizeof; // constantly
>> crashes :(
>>     float[COUNT] arr;
>>     writeln(arr.length);
>> }
>>
>> DMD: 2069.2
>> OS: Win 8.1 Pro
>
> The default stack size is probably 1MB, which means your 1MB array plus
> a few local variables is too much. Arrays that large should be allocated
> on the heap in most circumstances.
>
> Watch out for this:
> static assert(is(typeof(new float[3]) == float[]));
> because `new T[n]` is a special case in the grammar. If you really must
> have a static array on the heap (as opposed to a dynamic array / slice
> T[]), you can use something like this, but i wouldn't recommend it:
>
> T[N]* heapStaticArray(T, size_t N)()
> {
>      return cast(T[N]*)((new T[N]).ptr);
> }
>
> void main()
> {
>      int[4]* a = heapStaticArray!(int, 4)();
>      (*a)[] = 3;
> }

T[N]* heapStaticArray(T, size_t N)()
{
    auto arr = new T[N][1];
    return &arr[0];
}

-Steve


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