#14085: powModInteger sometimes ignores sign of argument -------------------------------------+------------------------------------- Reporter: ocheron | Owner: ocheron Type: bug | Status: new Priority: normal | Milestone: Component: Core Libraries | Version: 8.2.1 Resolution: | Keywords: integer-gmp Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D3826 Wiki Page: | -------------------------------------+------------------------------------- Comment (by ocheron): Working on a patch I found another issue with `gcdExtInteger` when first argument is negative. Program: {{{#!haskell {-# LANGUAGE MagicHash #-} {-# LANGUAGE UnboxedTuples #-} import GHC.Integer.GMP.Internals f a b = let (# g, s #) = gcdExtInteger a b in (g, s) main = do print $ f 100000000000000000000000000000 7 print $ f (-100000000000000000000000000000) 7 }}} crashes with assertion when executed: {{{ $ ghc -V && ghc --make a The Glorious Glasgow Haskell Compilation System, version 8.2.1 [1 of 1] Compiling Main ( a.hs, a.o ) Linking a ... $ ./a (1,3) Assertion failed: (sn <= xn), function integer_gmp_gcdext, file libraries /integer-gmp/cbits/wrappers.c, line 315. Abort trap: 6 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14085#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#14085: powModInteger sometimes ignores sign of argument -------------------------------------+------------------------------------- Reporter: ocheron | Owner: ocheron Type: bug | Status: new Priority: normal | Milestone: Component: Core Libraries | Version: 8.2.1 Resolution: | Keywords: integer-gmp Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D3826 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"c5605ae00e9bff90db7a5f24ff3b8de2aba3b55b/ghc" c5605ae0/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="c5605ae00e9bff90db7a5f24ff3b8de2aba3b55b" Make function intToSBigNat# preserve sign (fixes #14085) Impacts only functions gcdExtInteger, powModInteger and recipModInteger which gave invalid results on negative S# inputs. Also fixes gcdExtInteger assertion when first argument is negative. Test Plan: Updated test case integerGmpInternals Reviewers: austin, hvr, goldfire, bgamari Reviewed By: bgamari Subscribers: rwbarton, thomie GHC Trac Issues: #14085 Differential Revision: https://phabricator.haskell.org/D3826 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14085#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler