#12935: Object code produced by GHC is non-deterministic -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by nh2):
It's not an entirely trivial task. We use uniques quite often to name symbols in code produced by the native codegen. Fixing this without compromising compiler performance is rather tricky.
@bgamari Question: Why cannot the uniques be predetermined by a seed that's dependent on the module name? My understanding so far is this: We need an infinite stream of unused strings to generate symbols. Parallel compilation with `-j` and "partial" compilation of the projects (resumes, incremental compilation), means some number or pseudorandom generator has a different initial state when we come by the file next time. So couldn't we initialise the seed of that pseudorandom generator as `hash(module name)`, so that each time a module is compiled, it always generates the same uniques in the same order (as within a module there is no parallel compilation)? And when a module name changes, we have to recompile anyway and it's probably OK if the object code changes when that happens. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12935#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler