On Tuesday, 12 September 2017 at 09:11:20 UTC, Joseph wrote:
I have two nearly duplicate files I added a static this() to
initialize some static members of an interface.
On one file when I add an empty static this() it crashes while
the other one does not.
The exception that happens is
Cyclic dependency between module A and B.
Why does this occur on an empty static this? Is it being ran
twice or something? Anyway to fix this?
The compiler errors because the spec states [1]
Each module is assumed to depend on any imported modules being
statically constructed first
, which means two modules that import each other and both use
static construction have no valid static construction order.
One reason, I think, why the spec states that is because in
theory it would not always be possible for the compiler to decide
the order, e.g. when executing them changes the ("shared")
execution environment's state:
---
module a;
import b;
static this()
{
// Does something to the OS state
syscall_a();
}
---
---
module b;
import a;
static this()
{
// Also does something to the OS state
syscall_b();
}
---
The "fix" as I see it would be to either not use static
construction in modules that import each other, or propose a set
of rules for the spec that define a always solvable subset for
the compiler.
[1] https://dlang.org/spec/module.html#order_of_static_ctor
