Re: Where can find fix length array memory layout document
On Tuesday, 18 June 2019 at 12:26:14 UTC, lili wrote: Hi guys: Is the Dlang fix-length array alloc on stack? when a test writeln([1]).sizeof //16 writeln([2]).sizeof //16 Why, What is the fix-length array memory layout. You are quite confused... [...] is an array literal, not a static array. Those aren't the same thing. When you pass a array literal anywhere in your code, it will in principle be referred as a slice variable. This will not reallocate the contents. However the slice reference is another variable that takes up two words of space (see code below). This slice type is the same variable type that stores dynamic arrays -- be they allocated or null. Array literals are not necessarily allocated. The compiler is free to embed them into the program machine code itself. If you want a static array, you can just declare it directly e.g. int[n] arr. Of course you can also generate is out of an array literal with the staticArray std library function. PS the layout of D arrays is of course linear and contiguous. Both static or dynamic, just like C/C++ static arrays or std::vectors respectively. Hopefully this code makes things clear: /*/ enum lenInts = int.sizeof; static assert(lenInts == 4); int[1] arrStatic; static assert(lenInts == arrStatic.sizeof); auto slice = arrStatic[]; alias sliceType = typeof(slice); static assert(is(sliceType == int[])); enum lenPointers = size_t.sizeof; // fyi (unsinged) pointers static assert(ptrdiff_t.sizeof == lenPointers); // fyi signed pointer diff static assert(sliceType.sizeof == 2 * lenPointers); // because a D array reference remembers a pointer (like C) plus the length (stored in a word-length integer)
Re: Where can find fix length array memory layout document
On Wednesday, 19 June 2019 at 12:53:05 UTC, Cym13 wrote:
Did you import it properly?
```
void main() {
import core.stdcpp.array;
auto a = array!(int, 4)();
}
```
compiles and runs without issue for me. You'll have to show
your code if you want people to help you there.
Ok, where has some mistake in my code. thanks.
Re: Where can find fix length array memory layout document
On Wednesday, 19 June 2019 at 05:27:12 UTC, lili wrote:
On Tuesday, 18 June 2019 at 17:29:49 UTC, Cym13 wrote:
On Tuesday, 18 June 2019 at 17:25:42 UTC, Cym13 wrote:
On Tuesday, 18 June 2019 at 13:05:03 UTC, lili wrote:
On Tuesday, 18 June 2019 at 12:39:45 UTC, Dennis wrote:
[...]
Thanks a lot, where is a core.stdcpp.array , How to user it?
I test but get a error
```
auto aa = array!(int, 4); //error
```
Please don't shorten your code or errors to the point where
there's hardly any information left: it's hard to help you if
we can't know what you did and what went wrong.
Forgot to say that it's probably because you don't actually
build an array here, try adding parentheses:
```
auto aa = array!(int, 4)();
```
array!(int,4)(); compile occurs a error say: no overload
matches for array
Did you import it properly?
```
void main() {
import core.stdcpp.array;
auto a = array!(int, 4)();
}
```
compiles and runs without issue for me. You'll have to show your
code if you want people to help you there.
Re: Where can find fix length array memory layout document
On Tuesday, 18 June 2019 at 17:29:49 UTC, Cym13 wrote: On Tuesday, 18 June 2019 at 17:25:42 UTC, Cym13 wrote: On Tuesday, 18 June 2019 at 13:05:03 UTC, lili wrote: On Tuesday, 18 June 2019 at 12:39:45 UTC, Dennis wrote: [...] Thanks a lot, where is a core.stdcpp.array , How to user it? I test but get a error ``` auto aa = array!(int, 4); //error ``` Please don't shorten your code or errors to the point where there's hardly any information left: it's hard to help you if we can't know what you did and what went wrong. Forgot to say that it's probably because you don't actually build an array here, try adding parentheses: ``` auto aa = array!(int, 4)(); ``` array!(int,4)(); compile occurs a error say: no overload matches for array
Re: Where can find fix length array memory layout document
On Tuesday, 18 June 2019 at 17:25:42 UTC, Cym13 wrote: On Tuesday, 18 June 2019 at 13:05:03 UTC, lili wrote: On Tuesday, 18 June 2019 at 12:39:45 UTC, Dennis wrote: [...] Thanks a lot, where is a core.stdcpp.array , How to user it? I test but get a error ``` auto aa = array!(int, 4); //error ``` Please don't shorten your code or errors to the point where there's hardly any information left: it's hard to help you if we can't know what you did and what went wrong. Forgot to say that it's probably because you don't actually build an array here, try adding parentheses: ``` auto aa = array!(int, 4)(); ```
Re: Where can find fix length array memory layout document
On Tuesday, 18 June 2019 at 13:05:03 UTC, lili wrote: On Tuesday, 18 June 2019 at 12:39:45 UTC, Dennis wrote: On Tuesday, 18 June 2019 at 12:26:14 UTC, lili wrote: [...] I'm assuming you mean writeln([1].sizeof). An array literal is a slice of a dynamic array (which is length + pointer, so 2*size_t size). A fixed size array has to be declared as a local / member variable, and then the content is on the stack: ``` int[10] a; writeln(a.sizeof); // 40 writeln(a[].sizeof); // 16 on 64-bit or 8 on 32-bit ``` To get a static array literal, you can use the library function staticArray: ``` import std.array; writeln([1, 2, 3].staticArray.sizeof); // 12 ``` Thanks a lot, where is a core.stdcpp.array , How to user it? I test but get a error ``` auto aa = array!(int, 4); //error ``` Please don't shorten your code or errors to the point where there's hardly any information left: it's hard to help you if we can't know what you did and what went wrong.
Re: Where can find fix length array memory layout document
On Tuesday, 18 June 2019 at 12:39:45 UTC, Dennis wrote: On Tuesday, 18 June 2019 at 12:26:14 UTC, lili wrote: Hi guys: Is the Dlang fix-length array alloc on stack? when a test writeln([1]).sizeof //16 writeln([2]).sizeof //16 Why, What is the fix-length array memory layout. I'm assuming you mean writeln([1].sizeof). An array literal is a slice of a dynamic array (which is length + pointer, so 2*size_t size). A fixed size array has to be declared as a local / member variable, and then the content is on the stack: ``` int[10] a; writeln(a.sizeof); // 40 writeln(a[].sizeof); // 16 on 64-bit or 8 on 32-bit ``` To get a static array literal, you can use the library function staticArray: ``` import std.array; writeln([1, 2, 3].staticArray.sizeof); // 12 ``` Thanks a lot, where is a core.stdcpp.array , How to user it? I test but get a error ``` auto aa = array!(int, 4); //error ```
Re: Where can find fix length array memory layout document
On Tue, Jun 18, 2019 at 2:30 PM lili via Digitalmars-d-learn < digitalmars-d-learn@puremagic.com> wrote: > Hi guys: > Is the Dlang fix-length array alloc on stack? when a test > writeln([1]).sizeof //16 > writeln([2]).sizeof //16 > Why, What is the fix-length array memory layout. > When you do [1] without staticArray it will be automaticaly change to array slice which consist of pointer to data (8bytes on 64bit) and length of array again 8byte on 64bit
Re: Where can find fix length array memory layout document
On Tuesday, 18 June 2019 at 12:26:14 UTC, lili wrote: Hi guys: Is the Dlang fix-length array alloc on stack? when a test writeln([1]).sizeof //16 writeln([2]).sizeof //16 Why, What is the fix-length array memory layout. I'm assuming you mean writeln([1].sizeof). An array literal is a slice of a dynamic array (which is length + pointer, so 2*size_t size). A fixed size array has to be declared as a local / member variable, and then the content is on the stack: ``` int[10] a; writeln(a.sizeof); // 40 writeln(a[].sizeof); // 16 on 64-bit or 8 on 32-bit ``` To get a static array literal, you can use the library function staticArray: ``` import std.array; writeln([1, 2, 3].staticArray.sizeof); // 12 ```
Re: Where can find fix length array memory layout document
import std.stdio;
import std.array : staticArray;
void main() {
writeln([1].staticArray.sizeof); //4
writeln([2,5].staticArray.sizeof); //8
}
On Tue, Jun 18, 2019 at 2:30 PM lili via Digitalmars-d-learn <
digitalmars-d-learn@puremagic.com> wrote:
> Hi guys:
> Is the Dlang fix-length array alloc on stack? when a test
> writeln([1]).sizeof //16
> writeln([2]).sizeof //16
> Why, What is the fix-length array memory layout.
>
Where can find fix length array memory layout document
Hi guys: Is the Dlang fix-length array alloc on stack? when a test writeln([1]).sizeof //16 writeln([2]).sizeof //16 Why, What is the fix-length array memory layout.
