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Attempt to fix issue 23868
https://issues.dlang.org/show_bug.cgi?id=23868
Not sure if this is correct.
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Bugzilla references
Auto-close | Bugzilla | Severity | Description |
---|---|---|---|
✗ | 23868 | major | Compiler-generated opAssign has very high stack frame usage |
Testing this PR locally
If you don't have a local development environment setup, you can use Digger to test this PR:
dub run digger -- build "master + dmd#15148"
@WalterBright
This probably needs some extra work to make it exception-safe (what if exception is thrown in the dtor)
This probably needs some extra work to make it exception-safe (what if exception is thrown in the dtor)
This case wasn't treated previously either. Since we are not constructing anything I don't see why we would need to do anything extra.
This probably needs some extra work to make it exception-safe (what if exception is thrown in the dtor)
This case wasn't treated previously either. Since we are not constructing anything I don't see why we would need to do anything extra.
The state is different after exception is thrown in dtor:
Before: this
object contains new assigned object
After: this
object contains old value (on which the dtor failed). The assign object value is lost.
Testcase whose behavior changes with this change (i.e. I think the PR is wrong currently) :
import std.stdio;
import std.exception;
struct S {
int i;
~this() {
writeln("~S(", i, ")");
if (i == 1)
throw new Exception("thorw");
}
}
void main() {
S s;
s.i = 1;
try {
s = S(2);
} catch (Throwable) {}
writeln(s.i);
}
Without the change:
~S(1)
2
~S(2)
With this PR:
~S(1)
1
~S(1)
object.Exception@../dtor_throw.d(11): thorw
----------------
??:? void dtor_throw.S.__dtor() [0x100fd3689]
??:? _Dmain [0x100fd35ce]
The deconstructor should be nogc and nothrow by default here.
The deconstructor should be nogc and nothrow by default here.
Why? Is that a language requirement? (do you have a reference?)
Please see https://issues.dlang.org/show_bug.cgi?id=23868 which explains that this solution is not correct, and offers suggestions on how to avoid the issue.