Is comparison of shared data thread-safe?

[Nick Treleaven via Digitalmars-d-learn]

With -preview=nosharedaccess, I get:

int y = 2;
shared int x = y; // OK

assert(x == 2); // no error
y = x; // error

So for the assignment to y, reading x is an error and atomicLoad 
should be used instead. But is it an oversight that reading x in 
the assert is not an error?


I have also found this in a unittest in core.atomic:

shared(size_t) i;

atomicOp!"+="(i, cast(size_t) 1);
assert(i == 1);

Is the assert somehow thread-safe?

Re: Is comparison of shared data thread-safe?

[Nick Treleaven via Digitalmars-d-learn]

On Thursday, 16 March 2023 at 12:32:34 UTC, Nick Treleaven wrote:

With -preview=nosharedaccess, I get:

int y = 2;
shared int x = y; // OK

assert(x == 2); // no error
y = x; // error


This also does not error:
```d
bool b = x == 3;
```
Filed:
https://issues.dlang.org/show_bug.cgi?id=23783

Re: Is comparison of shared data thread-safe?

[bauss via Digitalmars-d-learn]

On Thursday, 16 March 2023 at 12:32:34 UTC, Nick Treleaven wrote:

With -preview=nosharedaccess, I get:

int y = 2;
shared int x = y; // OK

assert(x == 2); // no error
y = x; // error

So for the assignment to y, reading x is an error and 
atomicLoad should be used instead. But is it an oversight that 
reading x in the assert is not an error?


I have also found this in a unittest in core.atomic:

shared(size_t) i;

atomicOp!"+="(i, cast(size_t) 1);
assert(i == 1);

Is the assert somehow thread-safe?


I think it __should__ be fine since `i` cannot be in a state 
where it gets modified and read at the same time.