On Tuesday, 10 March 2020 at 10:02:16 UTC, Simen Kjærås wrote:
[snip]
As the error message hints at, the problem is Deb may hold
references to data that is shared with other objects on the
thread from which it originates. Since you know this is not the
case, even if the compiler can't prove it, you can safely cast
your Deb to immutable:
if (deb.valid)
send(parentTid, cast(immutable)deb.dup);
In fact, even the .dup is unnecessary here, since no data is
shared with other objects, so you can simply write
send(parentTid, cast(immutable)deb);. (Note on this point:
since you have not included all your code, it could be other
parts create shared mutable state, in which case .dup is
necessary, and if badly written may not be sufficient.
Thanks, that's led to some progress.
Once each Deb is populated its contents are never modified.
Nonetheless I've kept with .dup since I reuse the same Deb each
time to populate, then send a copy, then clear and reuse the
original.
Unfortunately, I'm now getting different errors:
src/model.d(85,30): Error: template std.concurrency.spawn cannot
deduce function from argument types !()(void delegate(Tid
parentTid, string filename), Tid, string), candidates are:
/home/mark/opt/ldc2-1.20.0-linux-x86_64/bin/../import/std/concurrency.d(460,5):
spawn(F, T...)(F fn, T args)
with F = void delegate(Tid, string),
T = (Tid, string)
must satisfy the following constraint:
isSpawnable!(F, T)
src/model.d(86,13): Warning: statement is not reachable
src/model.d(87,13): Warning: statement is not reachable
src/model.d(86,13): Warning: statement is not reachable
src/model.d(87,13): Warning: statement is not reachable
/home/mark/opt/ldc2-1.20.0-linux-x86_64/bin/../import/std/variant.d(701,26):
Error: cannot implicitly convert expression rhs of type immutable(Deb) to Deb
/home/mark/opt/ldc2-1.20.0-linux-x86_64/bin/../import/std/variant.d(603,17):
Error: template instance
std.variant.VariantN!32LU.VariantN.opAssign!(immutable(Deb)) error instantiating
/home/mark/opt/ldc2-1.20.0-linux-x86_64/bin/../import/std/concurrency.d(126,22):
instantiated from here: __ctor!(immutable(Deb))
/home/mark/opt/ldc2-1.20.0-linux-x86_64/bin/../import/std/concurrency.d(656,23):
instantiated from here: __ctor!(immutable(Deb))
/home/mark/opt/ldc2-1.20.0-linux-x86_64/bin/../import/std/concurrency.d(647,10):
instantiated from here: _send!(immutable(Deb))
/home/mark/opt/ldc2-1.20.0-linux-x86_64/bin/../import/std/concurrency.d(626,10):
instantiated from here: _send!(immutable(Deb))
src/model.d(115,21): instantiated from here:
send!(immutable(Deb))
/home/mark/opt/ldc2-1.20.0-linux-x86_64/bin/ldc2 failed with exit
code 1.
Should I be somehow casting away the immutable at the receive
end? (Even though received Debs are never modified?)
