On Thu, 29 Dec 2011 16:10:03 +1300, chrisyco@gmail.com wrote:
In fact, this is required behavior according to the Haskell Report:
Implementations should enforce as far as possible, at least locally to the Haskell process, multiple-reader single-writer locking on files. That is, there may either be many handles on the same file which manage input, or just one handle on the file which manages output.
The second sentence somewhat contradicts the first. The first sentence says, "multiple-reader single-writer" which implies multiple readers AND at most one writer (i.e., at the same time). This is pretty typical file-locking behavior, and, from the symptoms, appears to be the way that Framemaker opens the file. The second sentence, on the other hand, implies that there can be multiple readers OR one writer, but not both (which appears to be the way that GHC operates).
I guess on Windows, "as far as possible" means locking it across the whole system.
Windows does allow finer-grained control (including byte-range locking), but most applications don't bother. -Steve Schafer