On Wednesday, 16 October 2013 at 07:27:25 UTC, Namespace wrote:
On Wednesday, 16 October 2013 at 07:23:45 UTC, monarch_dodra
wrote:
On Tuesday, 15 October 2013 at 21:37:40 UTC, Namespace wrote:
I get this error:
----
/d701/f223.d(11): Error: pure function 'f223.getA' cannot
call impure function 'f223.A.~this'
----
with this code:
----
import std.stdio;
struct A {
public:
~this() {
writeln("DTor");
}
}
A getA() pure nothrow {
return A();
}
void main()
{
A a = getA();
writeln("end of main");
}
----
But without pure and nothrow I get this output:
----
end of main
DTor
----
Why the compiler thinks that the function should/could call
A::~this?
It could have something to do with the fact that RVO is an
optimization *opportunity* that the compiler is allowed to go
for, even if it changes the program output.
Hoewever, being an *opportunity*, the compiler still has to
make sure the code is valid without said optimization, which
in this case, isn't: getA would destroy it's temporary after
blitting it on the stac, leading to an impure call.
So it _could_ be impure, but mostly it isn't, right?
I guess that's one way to put it. I'd say it *is* impure, but all
its impure bits have been optimized out. That's my explanation
anyways.
I'm curious: Is this a problem for you? The function calling getA
*can't* be pure either, so marking getA as pure is ...
I was going to say useless, but I guess "pure" is always an
optimization opportunity for the compiler.
I'd file an ER, you never know.
