On 08/24/2011 03:35 PM, Timon Gehr wrote:
On 08/24/2011 03:13 PM, Alex Rønne Petersen wrote:
Hi,
This is an odd one. Consider the following code:
interface I
{
void foo()
out { assert(bar()); }
bool bar();
}
class C : I
{
void foo() {}
bool bar() { return true; }
}
void main()
{
C c = new C();
c.foo();
}
This will crash and burn when run:
object.Error: Access Violation
----------------
40DB64
40D9DB
402050
402074
4026F3
4022EF
4127B5
----------------
I assume this is a bug, but has anyone encountered this before or have
any idea why exactly it happens when calling other interface methods in
an interface method's out contract? (It seems to work fine in the in
contract.)
- Alex
I think it actually makes a lot of sense. I.foo's out contract assumes
an I this reference, but C.foo passes a C this reference without
adjustment. What I don't quite get yet is what is the matter with in
contracts on interface member functions. Not only do they not crash,
apparently they are not even executed.
Have you already filed a bug report?
This seems to confirm I was on the right path:
import std.stdio;
interface I
{
void foo()
out { writeln(typeid(this));}
bool bar();
final void qux(){ writeln(typeid(this)); }
}
class C : I
{
void foo() { }
bool bar() { return false; }
}
void main()
{
C c = new C();
c.qux(); // "modulename.I"
c.foo(); // "TypeInfo_Class", not sure why it is not modulename.C.
}
So, basically interfaces are the only place in D?/DMD where you can even
specify contracts without a function body and there they don't work. I
think the bug is not the only problem, actual contracts should /always/
be part of the function declaration and not require an implementation to
work. Everything else degrades contracts to simple syntactic sugar for
assertions.
