Segmentation fault after having a certain number of elements in an array?

[Steven Schveighoffer via Digitalmars-d-learn]

On 12/13/14 3:59 AM, Jeremy DeHaan wrote:
> I'll be trying to narrow it down even more tomorrow, but I was hoping
> somone here might have some insight into this weird issue I am having.
>
> I have a dynamic array of shorts that I had been trying to append to
> (capturing sound data). I kept getting a segfault when doing the append,
> and have narrowed it down to getting a segfault when the length of the
> array is equal to or greater than 1024.
>
> It looks wonky because of my many tests, but this is the code that was
> causing the segfault:
>
> override bool onProcessSamples(const(short)[] samples)
> {
>          import std.stdio;
>      for(int i = 0; i<samples.length; ++i)
>      {
>      writeln(m_samples.length);
>      m_samples.length +=1;
>      }
>      return true;
> }
>
> It will print all the numbers, endikng with 1023, and then it shows
> "Segmentation fault" and if I comment out the writeln line it just shows
> the Segmentation fault line. Similar code that would cause the length to
> be at 1024 or higher will also cause a segfault.
>
> The class that this method belongs to is wraped up in a C++ interface
> and it gets called C++ side.
>
> Also, if I set the length to 1024 or higher in the class constructor or
> if I create a different array elsewhere and set its length to 1024 or
> higher, I don't get the segfault anymore.
>
> As far as I can tell, this only happens because it is called in C++
> code. It doesn't appear to happen on my system at all if I do anything
> like this outside of my C++ interoperating. So far my fix is to set the
> length of the array to 1024, and then right away set it back to 0 in the
> class' constructor, but I'd like to get this to work without any strange
> hacks.

A guess -- is the class instantiated in C++? if so, it probably is not 
on the D heap, and probably is not scanned during GC collections. I 
think your m_samples array is reallocated during a collection, and you 
are using dangling memory.

Try GC.addRoot(this) at the start of the function, and see if it helps.

-Steve