#4012: Compilation results are not deterministic -------------------------------------+------------------------------------- Reporter: kili | Owner: niteria Type: bug | Status: patch Priority: high | Milestone: 8.0.1 Component: Compiler | Version: 6.12.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: | Blocking: Related Tickets: #10424 | Differential Rev(s): Phab:D910, | Phab:D1073, Phab:D1133, Phab:D1192, Wiki Page: | Phab:D1268 -------------------------------------+------------------------------------- Comment (by Ben Gamari <ben@…>): In [changeset:"158d2a91581d82dc1690a858b474eaab3a02e43e/ghc" 158d2a9/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="158d2a91581d82dc1690a858b474eaab3a02e43e" Make it possible to have different UniqSupply strategies To get reproducible/deterministic builds, the way that the Uniques are assigned shouldn't matter. This allows to test for that. It add 2 new flags: * `-dinitial-unique` * `-dunique-increment` And by varying these you can get interesting effects: * `-dinitial-unique=0 -dunique-increment 1` - current sequential UniqSupply * `-dinitial-unique=16777215 -dunique-increment -1` - UniqSupply that generates in decreasing order * `-dinitial-unique=1 -dunique-increment PRIME` - where PRIME big enough to overflow often - nonsequential order I haven't proven the usefullness of the last one yet and it's the reason why we have to mask the bits with `0xFFFFFF` in `genSym`, so I can remove it if it becomes contentious. Test Plan: validate on harbormaster Reviewers: simonmar, austin, ezyang, bgamari Reviewed By: austin, bgamari Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D1360 GHC Trac Issues: #4012 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4012#comment:127> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler