Michiel Helvensteijn wrote:
Rainer Deyke wrote:
I still find it silly that it was built that way. Seems to me you should
be able to forward-reference *any* symbol that has a value that can't
change over its lifetime. Functions, const/immutable vars, typedefs,
classes, etc.
That can lead to subtle problems in the case of functions:
int i = f();
int f() { return i; }
You're right, I forgot about that. You can conservatively statically forbid
this. But I admit it makes the 'constant data should obviously be
forward-referenceable' thing less convincing. :-)
I can't see how it can be done in the general case, other than by
constructing a dependency tree of top-level symbols.
Pass over the tree, evaluating everything which is a leaf of the tree.
If you have a pass where you don't succeed in removing any leaf nodes,
you have a circular dependency.
DMD sort of does this, I think, but it only does two passes, and it's
not very good at backing out when it discovers something is not a leaf.
It'd be hard to make that efficient when there are potentially infinite
passes.
