On Monday, 8 August 2022 at 12:45:20 UTC, bauss wrote:
On Monday, 8 August 2022 at 10:17:57 UTC, ag0aep6g wrote:
Never ever use `__gshared` ever.
[...]
To sum it up:
Single-write/Single-read?
__gshared
Single-write/Multi-read?
__gshared
Multi-write/Single-read?
shared
Multi-write/Multi-read?
shared
Nope. All of those can be race conditions.
Here's a single-write, single-read one:
```d
align(64) static struct S
{
align(1):
ubyte[60] off;
ulong x = 0;
}
__gshared S s;
void main()
{
import core.thread: Thread;
import std.conv: to;
new Thread(() {
foreach (i; 0 .. uint.max)
{
s.x = 0;
s.x = -1;
}
}).start();
foreach (i; 0 .. uint.max)
{
auto x = s.x;
assert(x == 0 || x == -1, to!string(x, 16));
}
}
```
If you know how to access the variable safely, you can do it with
`shared`.
I maintain: Never ever use `__gshared` ever.
