On Fri, Oct 22, 2004 at 05:13:02PM -0700, John Meacham wrote:
What happens when there are cicular dependencies between modules. Perhaps the circular dependency is only because of sharing of types, and there is a valid order for the initialization. But, is it easy for the compiler to determine this?
I don't see a problem with letting the compiler run them in an arbitrary order. I don't see much need for ordering things intermodule as long as the actions are executed in order within each module.
Although many programs will not depend on the ordering, others can. What if one module initialized a file, and another was expecting it to be setup correctly. Or, perhaps there is a shared IORef that needs to be initialized. Once IO is in the picture, the dependency computation can become complex. In general, if module A references module B, then module B's initialization should have finished before module B's. As long as there are no circular references, it isn't difficult to come up with a valid ordering (aside from references to external entities). When A and B each refer to the other, the compiler can't automatically determine which initialization must be done first. Dave