[Issue 11188] std.math.abs fails for shared BigInt type

[d-bugmail--- via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=11188

Basile-z  changed:

   What|Removed |Added

 CC|b2.t...@gmx.com |

--

[Issue 11188] std.math.abs fails for shared BigInt type

[d-bugmail--- via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=11188

Simen Kjaeraas  changed:

   What|Removed |Added

 Status|NEW |RESOLVED
 Resolution|--- |WONTFIX

--- Comment #14 from Simen Kjaeraas  ---
True - access to the BigInt would need to be protected somehow, and letting
abs(shared BigInt) simply compile without warning signals to the user that it's
perfectly safe, while tearing could still happen (unsynced ptr/length for the
data field, or wrong sign). The way shared works in D today, it's simply the
wrong choice. Thanks for enlightening me! :)

Closing this issue as wontfix because while important parts of the original
issue are fixed, the current name indicates shared only, and forcing the user
to cast (and thus hopefully think about locking or otherwise limiting access).

--

[Issue 11188] std.math.abs fails for shared BigInt type

[d-bugmail--- via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=11188

--- Comment #13 from anonymous4  ---
Indeed, but it's still big and shallow mutable. How would you avoid tearing? It
suggests different data layout with increased pressure on GC.

--

[Issue 11188] std.math.abs fails for shared BigInt type

[d-bugmail--- via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=11188

--- Comment #12 from Simen Kjaeraas  ---
(In reply to anonymous4 from comment #11)
> I think concurrency support is unreasonable here (and lacks rationale and
> use case). How it would work? Create a mutex for every BigInt?

BigInt internals are immutable, and abs takes its argument by value, so no
mutex is necessary.

For anyone who wants to fix this, the problem is not actually in std.math.abs,
but in BigInt - its operator overloads are not shared-aware.

--

[Issue 11188] std.math.abs fails for shared BigInt type

[d-bugmail--- via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=11188

--- Comment #11 from anonymous4  ---
I think concurrency support is unreasonable here (and lacks rationale and use
case). How it would work? Create a mutex for every BigInt?

--

[Issue 11188] std.math.abs fails for shared BigInt type

[d-bugmail--- via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=11188

b2.t...@gmx.com changed:

   What|Removed |Added

 CC||b2.t...@gmx.com
Summary|std.math.abs fails for  |std.math.abs fails for
   |shared, const or immutable  |shared BigInt type
   |BigInt types|

--- Comment #10 from b2.t...@gmx.com ---
Only valid for shared nowadays

import std.bigint, std.math, std.typetuple;

auto foo(T)()
{
T n = -3;
return std.math.abs(n);
}

void main()
{
foreach (T; TypeTuple!(byte, short, int, long, BigInt))
{
assert(foo!T() == 3); // works
assert(foo!(shared(T)) == 3); // fails for BigInt
}
}

The problem is that operator overloads don't accept shared

void main()
{
import std.bigint;
shared(BigInt) i = 0;
assert(i >= 0);
}

--