November 2014 - ghc-tickets

[GHC] #9820: Apparently inconsistent behaviour in the presence of OverlappingInstances
by GHC 15 Dec '15

15 Dec '15

#9820: Apparently inconsistent behaviour in the presence of OverlappingInstances -------------------------------------+------------------------------------- Reporter: kosmikus | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- This report is inspired by http://stackoverflow.com/questions/27051640 /strange-behavior-when-adding-constraint-to-instance I'm not sure if it is a bug, but it certainly feels strange and inconsistent to me, so I'd like to get some clarification. Here's a self-contained example of the behaviour: {{{#!hs {-# LANGUAGE FlexibleInstances, OverlappingInstances #-} module Overlap where class C a where foo :: a -> a instance C a where foo = id instance C Int where foo = (+1) -- Note that this one does not mention class C anywhere: class D a where bar :: a -> a instance D a where bar = foo -- this works and picks the 'C a' instance always -- The following does not compile without IncoherentInstances: {- baz :: a -> a baz = foo -} }}} I'm surprised that the definitions of `bar` and `baz` are treated differently. Shouldn't they either both require `IncoherentInstances`, or both work? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9820> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9846: GHC --make should also look for .hi, not only for .hs
by GHC 15 Dec '15

15 Dec '15

#9846: GHC --make should also look for .hi, not only for .hs -------------------------------------+------------------------------------- Reporter: larsrh | Owner: Type: feature request | Status: new Priority: normal | Milestone: ⊥ Component: Compiler | Version: Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Currently, `ghc --make` will only consider .hs source files from the include path. Example (assuming `Library` can't be resolved from the package database): `A.hs` {{{#!hs module A where import B import Library }}} `B.hs` {{{#!hs module B where }}} Compiling these files with `ghc --make -Idir A.hs B.hs` will succeed only if GHC finds a `Library.hs` file. In a thread on [https://www.haskell.org/pipermail/glasgow-haskell- users/2014-November/025476.html glasgow-haskell-users], Simon proposed relaxing this constraint; namely: In `--make` mode, when encountering an import `X`, GHC will try the following in order: 1. resolve the import from a package 2. search the include path for `X.hs` or `X.lhs` 3. search the include path for `X.hi` It already does 1 and 2, and this proposal would add 3. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9846> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8294: T7478 fails on Mac OS X with "unexpected bindingNone" from ld
by GHC 15 Dec '15

15 Dec '15

#8294: T7478 fails on Mac OS X with "unexpected bindingNone" from ld -----------------------------------+--------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHC API | Version: 7.7 Keywords: | Operating System: MacOS X Architecture: | Type of failure: Compile-time crash Unknown/Multiple | Test Case: T7478 Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | -----------------------------------+--------------------------------------- (Tangentially, the test script was swallowing up relevant output; you need to get rid of the output hook to see any debugging output from GHC proper). Linker step fails: {{{ *** Linker: /usr/bin/gcc -m64 -fno-stack-protector -DTABLES_NEXT_TO_CODE -m64 -v -o A -Wl,-no_compact_unwind C.o -L/Users/ezyang/Dev/ghc-init/libraries/base /dist-install/build -L/Users/ezyang/Dev/ghc-init/libraries/integer-gmp /dist-install/build -L/Users/ezyang/Dev/ghc-init/libraries/ghc-prim/dist- install/build -L/Users/ezyang/Dev/ghc-init/rts/dist/build /var/folders/l8/1lth36c11yg8dv_3kz779_th0000gn/T/ghc26290_0/ghc26290_10.o -lHSbase-4.7.0.0-ghc7.7.20130913 -lHSinteger-gmp-0.5.1.0-ghc7.7.20130913 -lHSghc-prim-0.3.1.0-ghc7.7.20130913 -lHSrts-ghc7.7.20130913 -lffi -liconv -lm -ldl -Wl,-u,_ghczmprim_GHCziTypes_Izh_static_info -Wl,-u,_ghczmprim_GHCziTypes_Czh_static_info -Wl,-u,_ghczmprim_GHCziTypes_Fzh_static_info -Wl,-u,_ghczmprim_GHCziTypes_Dzh_static_info -Wl,-u,_base_GHCziPtr_Ptr_static_info -Wl,-u,_ghczmprim_GHCziTypes_Wzh_static_info -Wl,-u,_base_GHCziInt_I8zh_static_info -Wl,-u,_base_GHCziInt_I16zh_static_info -Wl,-u,_base_GHCziInt_I32zh_static_info -Wl,-u,_base_GHCziInt_I64zh_static_info -Wl,-u,_base_GHCziWord_W8zh_static_info -Wl,-u,_base_GHCziWord_W16zh_static_info -Wl,-u,_base_GHCziWord_W32zh_static_info -Wl,-u,_base_GHCziWord_W64zh_static_info -Wl,-u,_base_GHCziStable_StablePtr_static_info -Wl,-u,_ghczmprim_GHCziTypes_Izh_con_info -Wl,-u,_ghczmprim_GHCziTypes_Czh_con_info -Wl,-u,_ghczmprim_GHCziTypes_Fzh_con_info -Wl,-u,_ghczmprim_GHCziTypes_Dzh_con_info -Wl,-u,_base_GHCziPtr_Ptr_con_info -Wl,-u,_base_GHCziPtr_FunPtr_con_info -Wl,-u,_base_GHCziStable_StablePtr_con_info -Wl,-u,_ghczmprim_GHCziTypes_False_closure -Wl,-u,_ghczmprim_GHCziTypes_True_closure -Wl,-u,_base_GHCziPack_unpackCString_closure -Wl,-u,_base_GHCziIOziException_stackOverflow_closure -Wl,-u,_base_GHCziIOziException_heapOverflow_closure -Wl,-u,_base_ControlziExceptionziBase_nonTermination_closure -Wl,-u,_base_GHCziIOziException_blockedIndefinitelyOnMVar_closure -Wl,-u,_base_GHCziIOziException_blockedIndefinitelyOnSTM_closure -Wl,-u,_base_ControlziExceptionziBase_nestedAtomically_closure -Wl,-u,_base_GHCziWeak_runFinalizzerBatch_closure -Wl,-u,_base_GHCziTopHandler_flushStdHandles_closure -Wl,-u,_base_GHCziTopHandler_runIO_closure -Wl,-u,_base_GHCziTopHandler_runNonIO_closure -Wl,-u,_base_GHCziConcziIO_ensureIOManagerIsRunning_closure -Wl,-u,_base_GHCziConcziIO_ioManagerCapabilitiesChanged_closure -Wl,-u,_base_GHCziConcziSync_runSparks_closure -Wl,-u,_base_GHCziConcziSignal_runHandlers_closure -Wl,-search_paths_first Using built-in specs. Target: i686-apple-darwin11 Configured with: /private/var/tmp/llvmgcc42/llvmgcc42-2336.11~182/src/configure --disable- checking --enable-werror --prefix=/Applications/Xcode.app/Contents/Developer/usr/llvm-gcc-4.2 --mandir=/share/man --enable-languages=c,objc,c++,obj-c++ --program- prefix=llvm- --program-transform-name=/^[cg][^.-]*$/s/$/-4.2/ --with- slibdir=/usr/lib --build=i686-apple-darwin11 --enable- llvm=/private/var/tmp/llvmgcc42/llvmgcc42-2336.11~182/dst- llvmCore/Developer/usr/local --program-prefix=i686-apple-darwin11- --host=x86_64-apple-darwin11 --target=i686-apple-darwin11 --with-gxx- include-dir=/usr/include/c++/4.2.1 Thread model: posix gcc version 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.11.00) /usr/llvm-gcc-4.2/bin/../libexec/gcc/i686-apple-darwin11/4.2.1/collect2 -dynamic -arch x86_64 -macosx_version_min 10.8.3 -weak_reference_mismatches non-weak -o A -lcrt1.10.6.o -L/Users/ezyang/Dev /ghc-init/libraries/base/dist-install/build -L/Users/ezyang/Dev/ghc- init/libraries/integer-gmp/dist-install/build -L/Users/ezyang/Dev/ghc- init/libraries/ghc-prim/dist-install/build -L/Users/ezyang/Dev/ghc- init/rts/dist/build -L/usr/llvm-gcc-4.2/bin/../lib/gcc/i686-apple- darwin11/4.2.1/x86_64 -L/Applications/Xcode.app/Contents/Developer/usr /llvm-gcc-4.2/lib/gcc/i686-apple-darwin11/4.2.1/x86_64 -L/usr/llvm- gcc-4.2/bin/../lib/gcc/i686-apple-darwin11/4.2.1 -L/usr/llvm- gcc-4.2/bin/../lib/gcc -L/Applications/Xcode.app/Contents/Developer/usr /llvm-gcc-4.2/lib/gcc/i686-apple-darwin11/4.2.1 -L/usr/llvm- gcc-4.2/bin/../lib/gcc/i686-apple-darwin11/4.2.1/../../.. -L/Applications/Xcode.app/Contents/Developer/usr/llvm-gcc-4.2/lib/gcc/i686 -apple-darwin11/4.2.1/../../.. -no_compact_unwind C.o /var/folders/l8/1lth36c11yg8dv_3kz779_th0000gn/T/ghc26290_0/ghc26290_10.o -lHSbase-4.7.0.0-ghc7.7.20130913 -lHSinteger-gmp-0.5.1.0-ghc7.7.20130913 -lHSghc-prim-0.3.1.0-ghc7.7.20130913 -lHSrts-ghc7.7.20130913 -lffi -liconv -lm -ldl -u _ghczmprim_GHCziTypes_Izh_static_info -u _ghczmprim_GHCziTypes_Czh_static_info -u _ghczmprim_GHCziTypes_Fzh_static_info -u _ghczmprim_GHCziTypes_Dzh_static_info -u _base_GHCziPtr_Ptr_static_info -u _ghczmprim_GHCziTypes_Wzh_static_info -u _base_GHCziInt_I8zh_static_info -u _base_GHCziInt_I16zh_static_info -u _base_GHCziInt_I32zh_static_info -u _base_GHCziInt_I64zh_static_info -u _base_GHCziWord_W8zh_static_info -u _base_GHCziWord_W16zh_static_info -u _base_GHCziWord_W32zh_static_info -u _base_GHCziWord_W64zh_static_info -u _base_GHCziStable_StablePtr_static_info -u _ghczmprim_GHCziTypes_Izh_con_info -u _ghczmprim_GHCziTypes_Czh_con_info -u _ghczmprim_GHCziTypes_Fzh_con_info -u _ghczmprim_GHCziTypes_Dzh_con_info -u _base_GHCziPtr_Ptr_con_info -u _base_GHCziPtr_FunPtr_con_info -u _base_GHCziStable_StablePtr_con_info -u _ghczmprim_GHCziTypes_False_closure -u _ghczmprim_GHCziTypes_True_closure -u _base_GHCziPack_unpackCString_closure -u _base_GHCziIOziException_stackOverflow_closure -u _base_GHCziIOziException_heapOverflow_closure -u _base_ControlziExceptionziBase_nonTermination_closure -u _base_GHCziIOziException_blockedIndefinitelyOnMVar_closure -u _base_GHCziIOziException_blockedIndefinitelyOnSTM_closure -u _base_ControlziExceptionziBase_nestedAtomically_closure -u _base_GHCziWeak_runFinalizzerBatch_closure -u _base_GHCziTopHandler_flushStdHandles_closure -u _base_GHCziTopHandler_runIO_closure -u _base_GHCziTopHandler_runNonIO_closure -u _base_GHCziConcziIO_ensureIOManagerIsRunning_closure -u _base_GHCziConcziIO_ioManagerCapabilitiesChanged_closure -u _base_GHCziConcziSync_runSparks_closure -u _base_GHCziConcziSignal_runHandlers_closure -search_paths_first -lSystem -lgcc -lSystem ld: warning: PIE disabled. Absolute addressing (perhaps -mdynamic-no-pic) not allowed in code signed PIE, but used in _Main_main_info from C.o. To fix this warning, don't compile with -mdynamic-no-pic or link with -Wl,-no_pie final section layout: __TEXT/__text addr=0x100000D30, size=0x00000218, fileOffset=0x00000D30, type=1 __TEXT/__stubs addr=0x100000F48, size=0x0000001E, fileOffset=0x00000F48, type=27 __TEXT/__stub_helper addr=0x100000F68, size=0x00000042, fileOffset=0x00000F68, type=31 __TEXT/__eh_frame addr=0x100000FB0, size=0x00000048, fileOffset=0x00000FB0, type=18 __DATA/__program_vars addr=0x100001000, size=0x00000028, fileOffset=0x00001000, type=29 __DATA/__got addr=0x100001028, size=0x00000020, fileOffset=0x00001028, type=28 __DATA/__nl_symbol_ptr addr=0x100001048, size=0x00000010, fileOffset=0x00001048, type=28 __DATA/__la_symbol_ptr addr=0x100001058, size=0x00000028, fileOffset=0x00001058, type=26 __DATA/__data addr=0x100001080, size=0x00000040, fileOffset=0x00001080, type=0 __DATA/__const addr=0x1000010C0, size=0x00000018, fileOffset=0x000010C0, type=0 __DATA/__common addr=0x1000010D8, size=0x00000020, fileOffset=0x00000000, type=24 ld: unexpected bindingNone in '_Main_main_info' from C.o for architecture x86_64 collect2: ld returned 1 exit status T7478: T7478: phase `Linker' failed (exitcode = 1) }}} Unfortunately, I don't know what a bindingNone is... -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8294> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9632: Promotable type synonyms (or: synonyms to promoted types)
by GHC 14 Dec '15

14 Dec '15

#9632: Promotable type synonyms (or: synonyms to promoted types) -------------------------------------+------------------------------------- Reporter: jstolarek | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: checker) | Operating System: Keywords: | Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Difficulty: Unknown | None/Unknown Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- I want to use '''synonyms to promoted types''' in the same places where I can use the '''promoted types''': {{{#!hs {-# LANGUAGE DataKinds, KindSignatures #-} module PromotableTypeSynonyms where data B = T | F data P :: B -> * type B' = B data P' :: B' -> * -- using B' synonym here is currently not allowed }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9632> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8566: Panic with kindFunResult
by GHC 12 Dec '15

12 Dec '15

#8566: Panic with kindFunResult ------------------------------------+------------------------------------- Reporter: dreixel | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- The following program: {{{ {-# LANGUAGE DataKinds #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeOperators #-} {-# LANGUAGE UndecidableInstances #-} {-# LANGUAGE MultiParamTypeClasses #-} module Bug where data U (s :: *) = forall k. AA k [U s] data I (u :: U *) (r :: [*]) :: * where A :: I (AA t as) r -- fs unused, but needs to be present for the bug class C (u :: U *) (r :: [*]) (fs :: [*]) where c :: I u r -> I u r instance (C (AA (t (I a ps)) as) ps fs) => C (AA t (a ': as)) ps fs where c A = c undefined }}} crashes a fresh copy of GHC HEAD with the following: {{{ ghc-stage2: panic! (the 'impossible' happened) (GHC version 7.7.20131126 for i386-unknown-linux): kindFunResult k1{tv a24f} [ssk] }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8566> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9017: Confusing error message with PolyKinds
by GHC 12 Dec '15

12 Dec '15

#9017: Confusing error message with PolyKinds ------------------------------------+------------------------------------- Reporter: edsko | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- Consider the following example code: {{{ import Control.Arrow foo :: a b (m b) foo = arr return }}} if we typecheck this we rightly get two errors about missing instances (Arrow a, Monad m). However, if we enable `PolyKinds` we get the following error message: {{{ T.hs:4:7: Kind incompatibility when matching types: a0 :: * -> * -> * a :: k1 -> k -> * Expected type: a b (m b) Actual type: a0 b0 (m0 b0) Relevant bindings include foo :: a b (m b) (bound at T.hs:4:1) In the expression: arr return In an equation for ‘foo’: foo = arr return }}} I can ''sort of'' see where this is coming from if I think really hard :), so perhaps it's not a bug per se, but it's definitely confusing; and it's a pity that a type error (forgotten type qualifier) is reported as a kind error. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9017> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9389: Full Test Suite Failures
by GHC 11 Dec '15

11 Dec '15

#9389: Full Test Suite Failures ------------------------------------+---------------------------------- Reporter: jrp | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Test Suite | Version: 7.8.3 Keywords: | Operating System: MacOS X Architecture: Unknown/Multiple | Type of failure: Other Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: ------------------------------------+---------------------------------- This is just to record progress on running the full test suite on OS X for the current HEAD using a BuildFlavour = perf build. I'll check through these (some of which are configuration issues because of the non-standard build or some required libraries are not being pulled in). {{{ OVERALL SUMMARY for test run started at Thu Jul 31 23:03:39 2014 BST 0:32:31 spent to go through 4036 total tests, which gave rise to 19262 test cases, of which 4218 were skipped 358 had missing libraries 14485 expected passes 135 expected failures 0 caused framework failures 0 unexpected passes 66 unexpected failures Unexpected failures: ../../libraries/base/tests enum01 [exit code non-0] (normal,hpc,optasm,profasm,threaded1,threaded2,dyn,profthreaded,optllvm) ../../libraries/base/tests enum01 [bad stdout or stderr] (ghci) ../../libraries/base/tests enum02 [exit code non-0] (normal,hpc,optasm,profasm,threaded1,threaded2,dyn,profthreaded,optllvm) ../../libraries/base/tests enum02 [bad stdout or stderr] (ghci) ../../libraries/base/tests enum03 [exit code non-0] (normal,hpc,optasm,profasm,threaded1,threaded2,dyn,profthreaded,optllvm) ../../libraries/base/tests enum03 [bad stdout or stderr] (ghci) ../../libraries/unix/tests signals004 [bad exit code] (threaded2) concurrent/should_run T367_letnoescape [bad exit code] (optllvm) concurrent/should_run conc012 [bad exit code] (ghci) driver/objc objc-hi [bad profile] (profthreaded) driver/objc objc-hi [bad heap profile] (profasm) driver/objc objcpp-hi [bad profile] (profthreaded) driver/objc objcpp-hi [bad heap profile] (profasm) ffi/should_run ffi002 [bad exit code] (threaded2) indexed-types/should_compile T7837 [stderr mismatch] (profasm) perf/compiler T4801 [stat too good] (normal) perf/haddock haddock.base [stat not good enough] (normal) perf/should_run T9203 [stat too good] (normal) profiling/should_run callstack001 [bad stdout] (prof) quasiquotation/qq007 qq007 [exit code non-0] (profasm) quasiquotation/qq008 qq008 [exit code non-0] (profasm) rts T5435_dyn_asm [bad stdout] (normal) rts T7919 [exit code non-0] (profasm,profthreaded) rts T9078 [exit code non-0] (profasm) rts derefnull [bad profile] (profasm,profthreaded) rts divbyzero [bad profile] (profasm,profthreaded) rts overflow1 [bad exit code] (hpc,optasm,profasm,threaded2,dyn,profthreaded,optllvm) rts overflow2 [bad profile] (profasm,profthreaded) rts overflow3 [bad profile] (profasm,profthreaded) simplCore/should_compile T5550 [exit code non-0] (profasm) simplCore/should_compile T7702 [exit code non-0] (profasm) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9389> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8245: ghc-pkg list prints packages in non-alphabetical order
by GHC 07 Dec '15

07 Dec '15

#8245: ghc-pkg list prints packages in non-alphabetical order ------------------------------------+------------------------------------- Reporter: nh2 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- Instead, it prints the ones with the smallest version first. That does not make much sense. I will attach a patch. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8245> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9015: A documented way to differentiate between statements, declarations, imports, etc.
by GHC 07 Dec '15

07 Dec '15

#9015: A documented way to differentiate between statements, declarations, imports, etc. -------------------------------------+------------------------------------- Reporter: splinterofchaos | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: GHC API | Version: 7.8.2 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Documentation Difficulty: Moderate (less | bug than a day) | Test Case: Blocked By: | Blocking: Related Tickets: | -------------------------------------+------------------------------------- I'm working on a little REPL and the GHC API seems to supply two functions for evaluating one line, without compiling and evaluating into an `HValue`, which doesn't seem to have an `Outputable` instace: `runStmt` and `runDecls`. As it turns out, I need slightly different code to run on declarations verses statements, so this makes sense, but given a random string from the user, how can I tell the difference? I don't see anything in the documentation about this. I took a look at ghci's source (https://github.com/ghc/ghc/blob/a6f2c852d49313fa8acea2deb3741ab86c6ef995/gh…] and it looks like they just peek at the first word of the input, and that may be correct and sufficient, but impossible to verify without looking at Haskell's grammar. But even if I did verify it, that doesn't make explicit the difference between what `runDecls` and `runStmt` will accept. For a contrived example, consider if GHC implemented a feature that allowed for a new type of decl. It might be enabled by a language extension which means that testing whether a string is a statement or declaration cannot be done purely as we have to check the dynflags. Furthermore, the client may not be aware of the extension and thus send the input to `runStmt` instead. It would seem to me that requiring the user to manually parse the input violates separation of concerns since truly GHC knows best what source GHC will accept. The user should not have to examine the input except for if they need to modify or interpret it as something other than Haskell source code. The GHC API should either document an example function for differentiating declarations from statements (and even import statements), supply one itself, or supply several along the lines of `isDecl, isStmt, isImport :: String -> Bool`. This would improve ease-of-use by making client code more obvious and correct. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9015> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9706: New block-structured heap organization for 64-bit
by GHC 05 Dec '15

05 Dec '15

#9706: New block-structured heap organization for 64-bit -------------------------------------+------------------------------------- Reporter: ezyang | Owner: simonmar Type: task | Status: new Priority: normal | Milestone: Component: Runtime System | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- I was having some discussion about GHC's block structured heap with Sergio Benitez and Adam Belay, and during the discussion it was suggested that the way GHC manages the block structured heap is suboptimal when we're on 64-bit architectures. At the moment, we allocate memory from the operating system per-megablock, storing metadata in the very first megablock. We have to do this because, on 32-bit, we can't generally be too picky about what address our memory ends up living. On 64-bits, we have a lot more flexibility. Here is the proposal: 1. Statically decide on a maximum heap size in a power of two. 2. Next, probe for some appropriately aligned chunk of available virtual address space for this. On POSIX, we can mmap /dev/null using PROT_NONE and MAP_NORESERVE. On Windows, we can use VirtualAlloc with MEM_RESERVE. (There are few other runtimes which do this trick, including GCC Go.) 3. Divide this region into blocks as before. The maximum heap size is now the megablock size, and the block size is still the same as before. Masking to find the block descriptor works as before. 4. To allocate, we keep track of the high-watermark, and mmap in 1MB pages as they are requested. We also keep track of how much metadata we need, and mmap extra pages to store metadata as necessary. We still want to request memory from the operating system in conveniently sized chunks, but we can now abolish the notion of a megablock and the megablock allocator, and work purely with block coalescing. Additionally, the recorded heap location means that we can check if a pointer is HEAP_ALLOCED using a mask and equality check, solving #8199. What do people think? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9706> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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