Re: Is it possible to modify shared struct array in a function.
On Friday, February 8, 2019 4:27:44 AM MST Eduard Staniloiu via Digitalmars-
d-learn wrote:
> On Friday, 8 February 2019 at 06:55:15 UTC, Jerry wrote:
> > On Friday, 8 February 2019 at 04:51:08 UTC, Sudhi wrote:
> >> On Friday, 8 February 2019 at 04:30:23 UTC, Arun
> >>
> >> Chandrasekaran wrote:
> >>> On Friday, 8 February 2019 at 04:13:39 UTC, Sudhi wrote:
> [...]
> >>>
> >>> Works fine for me with DMD64 D Compiler v2.083.1.
> >>> https://run.dlang.io/is/RRM8GU
> >>
> >> My example code was wrong. Below is the right one.
> >>
> >> struct Company
> >> {
> >>
> >> string name;
> >> string location;
> >>
> >> }
> >>
> >> struct Racks
> >> {
> >>
> >> int number;
> >> int location;
> >>
> >> }
> >>
> >> struct Metadata
> >> {
> >>
> >> string name;
> >> Company[] companies;
> >> Racks[] racks;
> >>
> >> }
> >>
> >> struct Item
> >> {
> >>
> >> Metadata[] met;
> >> int count;
> >>
> >> }
> >>
> >> shared (Item) item;
> >>
> >> void main()
> >> {
> >>
> >>updateMetadata();
> >>
> >> }
> >>
> >> void updateMetadata()
> >> {
> >>
> >>Company company;
> >>company.name = "Hello";
> >>company.location = "Bangalore";
> >>item.met.companies ~= company;
> >>import std.stdio: writeln;
> >>writeln(item);
> >>
> >> }
> >>
> >> https://run.dlang.io/is/iem0PY
> >
> > You have to cast away shared:
> >
> > auto loc_item = cast(Item) item;
> > loc_item.met ~= m;
> > item = cast(shared) loc_item;
> >
> > Just to be clear, this is not threadsafe and require a mutex if
> > you do this other than as init in main.
>
> You do not need to cast away shared. You had a couple of issues
> with your `updateMetadata()` function.
>
> First of, `met` is an array, so you need to index it: your code
> `item.met.companies ~= company` becomes `item.met[0].companies ~=
> company`. This will compile, but throw a range error because you
> don't have any `Metadata` object in your `met` array.
>
> I have typed below the revised form of your function
>
> ```
> void updateMetadata()
> {
> // create a Company instance. This must be shared
> shared Company company;
> company.name = "Hello";
> company.location = "Bangalore";
>
> // create a shared Metadata instance
> shared Metadata m;
> m.name = "m";
>
> // append m to the array of meta
> item.met ~= m;
> // append the company to the array of companies, for a given
> meta
> item.met[0].companies ~= company;
>
> import std.stdio: writeln;
> writeln(item);
> }
> ```
>
> The working version is at https://run.dlang.io/is/RvRKrU
>
> Cheers,
> Edi
Honestly, the fact that that code compiles is a bug. You're not supposed to
be able to modify shared objects in a manner which isn't guaranteed to be
atomic, because it's not thread-safe. The compiler catches it in a number of
places, but there are many where it currently doesn't.
But regardless of whether the compiler allows such mutation, a mutex (or
similar protection mechanism) needs to be used in order to make the code
thread-safe.
- Jonathan M Davis
Re: Is it possible to modify shared struct array in a function.
On Friday, 8 February 2019 at 06:55:15 UTC, Jerry wrote:
On Friday, 8 February 2019 at 04:51:08 UTC, Sudhi wrote:
On Friday, 8 February 2019 at 04:30:23 UTC, Arun
Chandrasekaran wrote:
On Friday, 8 February 2019 at 04:13:39 UTC, Sudhi wrote:
[...]
Works fine for me with DMD64 D Compiler v2.083.1.
https://run.dlang.io/is/RRM8GU
My example code was wrong. Below is the right one.
struct Company
{
string name;
string location;
}
struct Racks
{
int number;
int location;
}
struct Metadata
{
string name;
Company[] companies;
Racks[] racks;
}
struct Item
{
Metadata[] met;
int count;
}
shared (Item) item;
void main()
{
updateMetadata();
}
void updateMetadata()
{
Company company;
company.name = "Hello";
company.location = "Bangalore";
item.met.companies ~= company;
import std.stdio: writeln;
writeln(item);
}
https://run.dlang.io/is/iem0PY
You have to cast away shared:
auto loc_item = cast(Item) item;
loc_item.met ~= m;
item = cast(shared) loc_item;
Just to be clear, this is not threadsafe and require a mutex if
you do this other than as init in main.
You do not need to cast away shared. You had a couple of issues
with your `updateMetadata()` function.
First of, `met` is an array, so you need to index it: your code
`item.met.companies ~= company` becomes `item.met[0].companies ~=
company`. This will compile, but throw a range error because you
don't have any `Metadata` object in your `met` array.
I have typed below the revised form of your function
```
void updateMetadata()
{
// create a Company instance. This must be shared
shared Company company;
company.name = "Hello";
company.location = "Bangalore";
// create a shared Metadata instance
shared Metadata m;
m.name = "m";
// append m to the array of meta
item.met ~= m;
// append the company to the array of companies, for a given
meta
item.met[0].companies ~= company;
import std.stdio: writeln;
writeln(item);
}
```
The working version is at https://run.dlang.io/is/RvRKrU
Cheers,
Edi
Re: Is it possible to modify shared struct array in a function.
On Friday, 8 February 2019 at 04:51:08 UTC, Sudhi wrote:
On Friday, 8 February 2019 at 04:30:23 UTC, Arun Chandrasekaran
wrote:
On Friday, 8 February 2019 at 04:13:39 UTC, Sudhi wrote:
[...]
Works fine for me with DMD64 D Compiler v2.083.1.
https://run.dlang.io/is/RRM8GU
My example code was wrong. Below is the right one.
struct Company
{
string name;
string location;
}
struct Racks
{
int number;
int location;
}
struct Metadata
{
string name;
Company[] companies;
Racks[] racks;
}
struct Item
{
Metadata[] met;
int count;
}
shared (Item) item;
void main()
{
updateMetadata();
}
void updateMetadata()
{
Company company;
company.name = "Hello";
company.location = "Bangalore";
item.met.companies ~= company;
import std.stdio: writeln;
writeln(item);
}
https://run.dlang.io/is/iem0PY
You have to cast away shared:
auto loc_item = cast(Item) item;
loc_item.met ~= m;
item = cast(shared) loc_item;
Just to be clear, this is not threadsafe and require a mutex if
you do this other than as init in main.
Re: Is it possible to modify shared struct array in a function.
On Friday, 8 February 2019 at 04:51:08 UTC, Sudhi wrote:
On Friday, 8 February 2019 at 04:30:23 UTC, Arun Chandrasekaran
wrote:
[...]
My example code was wrong. Below is the right one.
struct Company
{
string name;
string location;
}
struct Racks
{
int number;
int location;
}
struct Metadata
{
string name;
Company[] companies;
Racks[] racks;
}
struct Item
{
Metadata[] met;
int count;
}
shared (Item) item;
void main()
{
updateMetadata();
}
void updateMetadata()
{
Company company;
company.name = "Hello";
company.location = "Bangalore";
item.met.companies ~= company;
import std.stdio: writeln;
writeln(item);
}
https://run.dlang.io/is/iem0PY
`shared struct Metadata` should make it work.
Turtles (shared) all the way down.
Re: Is it possible to modify shared struct array in a function.
On Friday, 8 February 2019 at 04:30:23 UTC, Arun Chandrasekaran
wrote:
On Friday, 8 February 2019 at 04:13:39 UTC, Sudhi wrote:
I have a situation, where i want to modify a shared variable
in a function. Something like below
struct Company
{
string name;
string location;
}
struct Racks
{
int number;
int location;
}
struct Metadata
{
string name;
Company[] companies;
Racks[] racks;
}
struct Item
{
Metadata met;
int count;
}
shared (Item) item
void main()
{
updateMetadata()
}
void updateMetadata()
{
Company company;
company.name = "Hello";
company.location = "Bangalore";
item.met.companies ~= company;
}
Compiler throws me error in last line for appending as below.
"cannot append type Metadata to type shared(Metadata[])".
Please let me know if there is a way to acheive this.
Thanks,
Sudhi
Works fine for me with DMD64 D Compiler v2.083.1.
https://run.dlang.io/is/RRM8GU
My example code was wrong. Below is the right one.
struct Company
{
string name;
string location;
}
struct Racks
{
int number;
int location;
}
struct Metadata
{
string name;
Company[] companies;
Racks[] racks;
}
struct Item
{
Metadata[] met;
int count;
}
shared (Item) item;
void main()
{
updateMetadata();
}
void updateMetadata()
{
Company company;
company.name = "Hello";
company.location = "Bangalore";
item.met.companies ~= company;
import std.stdio: writeln;
writeln(item);
}
https://run.dlang.io/is/iem0PY
Re: Is it possible to modify shared struct array in a function.
On Friday, 8 February 2019 at 04:13:39 UTC, Sudhi wrote:
I have a situation, where i want to modify a shared variable in
a function. Something like below
struct Company
{
string name;
string location;
}
struct Racks
{
int number;
int location;
}
struct Metadata
{
string name;
Company[] companies;
Racks[] racks;
}
struct Item
{
Metadata met;
int count;
}
shared (Item) item
void main()
{
updateMetadata()
}
void updateMetadata()
{
Company company;
company.name = "Hello";
company.location = "Bangalore";
item.met.companies ~= company;
}
Compiler throws me error in last line for appending as below.
"cannot append type Metadata to type shared(Metadata[])".
Please let me know if there is a way to acheive this.
Thanks,
Sudhi
Works fine for me with DMD64 D Compiler v2.083.1.
https://run.dlang.io/is/RRM8GU
