#8425: ghc-7.6.3: crossmodule inline leads to buggy code (-O2) ----------------------------------+------------------------------------- Reporter: slyfox | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: x86_64 (amd64) | Type of failure: Runtime crash Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ----------------------------------+------------------------------------- The bug is found as a crash of gf-3.4 ('Grammatical Framework') package compiled with -O2. With some debugging I've come to roughly following minimal example: This code compiles incorrectly: {{{ import BuggyOpt() -- bug inducer! import qualified Data.Map as Map import Data.Array.IArray {-# NOINLINE mkLin #-} mkLin :: Array Int (Array Int Int) -> Map.Map (Array Int Int) Int -> Int -> (Map.Map (Array Int Int) Int, Int) mkLin mseqs seqs seqid = let seq_ = mseqs ! seqid -- lookup/insert pair. exactly as in 'BuggyOpt' module in case Map.lookup seq_ seqs of Just seqid' -> (seqs,seqid') Nothing -> let seqid'' = Map.size seqs seqs' = Map.insert seq_ seqid'' seqs in (seqs',seqid'') }}} And this works fine: {{{ --import BuggyOpt() -- bug inducer! import qualified Data.Map as Map import Data.Array.IArray {-# NOINLINE mkLin #-} mkLin :: Array Int (Array Int Int) -> Map.Map (Array Int Int) Int -> Int -> (Map.Map (Array Int Int) Int, Int) mkLin mseqs seqs seqid = let seq_ = mseqs ! seqid -- lookup/insert pair. exactly as in 'BuggyOpt' module in case Map.lookup seq_ seqs of Just seqid' -> (seqs,seqid') Nothing -> let seqid'' = Map.size seqs seqs' = Map.insert seq_ seqid'' seqs in (seqs',seqid'') }}} Attached minimal test tarball and my results on it are: {{{ [("Project name","The Glorious Glasgow Haskell Compilation System") ,("GCC extra via C opts"," -fwrapv") ,("C compiler command","x86_64-pc-linux-gnu-gcc") ,("C compiler flags"," -fno-stack-protector -Wl,--hash-size=31 -Wl ,--reduce-memory-overheads") ,("ar command","/usr/bin/ar") ,("ar flags","q") ,("ar supports at file","YES") ,("touch command","touch") ,("dllwrap command","/bin/false") ,("windres command","/bin/false") ,("perl command","/usr/bin/perl") ,("target os","OSLinux") ,("target arch","ArchX86_64") ,("target word size","8") ,("target has GNU nonexec stack","True") ,("target has .ident directive","True") ,("target has subsections via symbols","False") ,("LLVM llc command","/usr/bin/llc") ,("LLVM opt command","/usr/bin/opt") ,("Project version","7.6.3") ,("Booter version","7.6.3") ,("Stage","2") ,("Build platform","x86_64-unknown-linux") ,("Host platform","x86_64-unknown-linux") ,("Target platform","x86_64-unknown-linux") ,("Have interpreter","YES") ,("Object splitting supported","YES") ,("Have native code generator","YES") ,("Support SMP","YES") ,("Unregisterised","NO") ,("Tables next to code","YES") ,("RTS ways","l debug thr thr_debug thr_l thr_p dyn debug_dyn thr_dyn thr_debug_dyn") ,("Leading underscore","NO") ,("Debug on","False") ,("LibDir","/usr/lib64/ghc-7.6.3") ,("Global Package DB","/usr/lib64/ghc-7.6.3/package.conf.d") ,("Gcc Linker flags","[\"-Wl,--hash-size=31\",\"-Wl,--reduce-memory- overheads\"]") ,("Ld Linker flags","[\"--hash-size=31\",\"--reduce-memory-overheads\"]") ] RUN good [1 of 2] Compiling Susp ( good/Susp.hs, good/Susp.o ) [2 of 2] Compiling Main ( good/main.hs, good/main.o ) Linking good/main ... (fromList [(array (0,0) [(0,42)],0)],0) RUN bad [1 of 3] Compiling BuggyOpt ( bad/BuggyOpt.hs, bad/BuggyOpt.o ) [2 of 3] Compiling Susp ( bad/Susp.hs, bad/Susp.o ) [3 of 3] Compiling Main ( bad/main.hs, bad/main.o ) Linking bad/main ... main: Error in array index; 0 not in range [0..0) TEST FAILED in bad }}} What we see here is the test with useless import mysteriously fails:
main: Error in array index; 0 not in range [0..0)
while without import it works fine:
(fromList [(array (0,0) [(0,42)],0)],0)
The functions in both BuggyOpt and Susp modules contain suspiciously similar code: {{{ case Map.lookup seq' seqs of Just id' -> (seqs,id') Nothing -> let last_seq = Map.size seqs in (Map.insert seq' last_seq seqs, last_seq) }}} But in BuggyOpt ghc somehow deduces some arguments and applies that effect to (unrelated, but looking similar) Susp module. Thanks! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8425 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler