If structures placing data on the stack why we do not getting stackoveflow while we creating array of structures? Or for example big structure.

Am I right understand that structures placing data _only_ on stack? But the stack size is very limited (on Widnows it's just 1MB).

So how it's work?

On 16/08/2017 8:06 AM, Suliman wrote:
> If structures placing data on the stack why we do not getting stackoveflow while we creating array of structures? Or for example big structure.
> 
> Am I right understand that structures placing data _only_ on stack? But the stack size is very limited (on Widnows it's just 1MB).
> 
> So how it's work?

Struct's by themselves go on the stack.
If they are allocated via new/malloc its on the heap (and hence are pointers).
Same situation with arrays or inside a class.

On Wednesday, 16 August 2017 at 07:09:02 UTC, rikki cattermole wrote:
> On 16/08/2017 8:06 AM, Suliman wrote:
>> If structures placing data on the stack why we do not getting stackoveflow while we creating array of structures? Or for example big structure.
>> 
>> Am I right understand that structures placing data _only_ on stack? But the stack size is very limited (on Widnows it's just 1MB).
>> 
>> So how it's work?
>
> Struct's by themselves go on the stack.
> If they are allocated via new/malloc its on the heap (and hence are pointers).
> Same situation with arrays or inside a class.

But for example if I am getting array of structs and getting data to it, where it's locating?

On 16/08/2017 8:14 AM, Suliman wrote:
> On Wednesday, 16 August 2017 at 07:09:02 UTC, rikki cattermole wrote:
>> On 16/08/2017 8:06 AM, Suliman wrote:
>>> If structures placing data on the stack why we do not getting stackoveflow while we creating array of structures? Or for example big structure.
>>>
>>> Am I right understand that structures placing data _only_ on stack? But the stack size is very limited (on Widnows it's just 1MB).
>>>
>>> So how it's work?
>>
>> Struct's by themselves go on the stack.
>> If they are allocated via new/malloc its on the heap (and hence are pointers).
>> Same situation with arrays or inside a class.
> 
> But for example if I am getting array of structs and getting data to it, where it's locating?

On the heap, unless you are allocating it via e.g. alloca.

> On the heap, unless you are allocating it via e.g. alloca.

If
struct MyStruct
{
 int x;
 int y;
}

MyStruct mystruct;

is located on stack, why:

MyStruct [] mystructs;

should located on heap?

On Wednesday, 16 August 2017 at 07:39:01 UTC, Suliman wrote:
>> On the heap, unless you are allocating it via e.g. alloca.
>
> If
> struct MyStruct
> {
>  int x;
>  int y;
> }
>
> MyStruct mystruct;
>
> is located on stack, why:
>
> MyStruct [] mystructs;
>
> should located on heap?

because in D

MyStruct [] mystructs;

is the equivalent of

struct {
   MyStruct *ptr;
   size_t size;
}

On Wednesday, 16 August 2017 at 07:39:01 UTC, Suliman wrote:
>> On the heap, unless you are allocating it via e.g. alloca.
>
> If
> struct MyStruct
> {
>  int x;
>  int y;
> }
>
> MyStruct mystruct;
>
> is located on stack, why:
>
> MyStruct [] mystructs;
>
> should located on heap?

MyStruct[] is actually a struct similar to this:

struct MyStruct[] {
    MyStruct* ptr;
    size_t length;
}

That struct is placed on the stack, but the data it points to, via the ptr field, is heap allocated.

One explanation of why is that the compiler doesn't know how many elements are in the array, and that that number may change. If it was stack-allocated and a new element was added to the array, everything on the stack would have to be moved.

If the compiler does know the number of elements, it can allocate the array on the stack (theoretically, this could be done as an optimization, but in practice I don't think it is). You can give the compiler this information:

MyStruct[10] mystructs;

This will allocate 10 MyStructs (80 bytes) on the stack, and if you change 10 to a large number, will give a stack overflow.

--
  Biotronic

> MyStruct[] is actually a struct similar to this:
>
> struct MyStruct[] {
>     MyStruct* ptr;
>     size_t length;
> }
>
> That struct is placed on the stack, but the data it points to, via the ptr field, is heap allocated.

What is struct? Just name and size?

On Wednesday, 16 August 2017 at 12:50:07 UTC, Suliman wrote:
>> MyStruct[] is actually a struct similar to this:
>>
>> struct MyStruct[] {
>>     MyStruct* ptr;
>>     size_t length;
>> }
>>
>> That struct is placed on the stack, but the data it points to, via the ptr field, is heap allocated.
>
> What is struct? Just name and size?

I'm sorry, I don't understand what you're asking. Can you please repeat with more information?

--
  Biotronic

On Wednesday, 16 August 2017 at 13:41:29 UTC, Biotronic wrote:
> On Wednesday, 16 August 2017 at 12:50:07 UTC, Suliman wrote:
>>> MyStruct[] is actually a struct similar to this:
>>>
>>> struct MyStruct[] {
>>>     MyStruct* ptr;
>>>     size_t length;
>>> }
>>>
>>> That struct is placed on the stack, but the data it points to, via the ptr field, is heap allocated.
>>
>> What is struct? Just name and size?
>
> I'm sorry, I don't understand what you're asking. Can you please repeat with more information?
>
> --
>   Biotronic

I am trying to understand what structure is. It's name + associated with this name data? I can't understand for my self what mean no put structure to stack. Just put it's name to it or something another?