November 2017 - ghc-tickets

[GHC] #12152: panic: Loading temp shared object failed
by GHC 03 Jun '18

03 Jun '18

#12152: panic: Loading temp shared object failed -------------------------------------+------------------------------------- Reporter: crockeea | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 (Linking) | Keywords: | Operating System: Linux Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I've attached a no-Haskell-code project that fails when I run `cabal repl` with the following: {{{ ghc: panic! (the 'impossible' happened) (GHC version 7.10.3 for x86_64-unknown-linux): Loading temp shared object failed: /tmp/ghc60744_0/libghc_1.so: undefined symbol: _ZN2Zq1qE }}} Building the project works fine, so the problem seems to be (only) with dynamic linking. The issue can be resolved by swapping the order of the .cpp files in the cabal file. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12152> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14546: -Woverlapping-patterns warns on wrong patterns for Int
by GHC 03 Jun '18

03 Jun '18

#14546: -Woverlapping-patterns warns on wrong patterns for Int -------------------------------------+------------------------------------- Reporter: Lemming | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect Unknown/Multiple | error/warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- GHC-8.0 introduced a new warning on redundant pattern matches in `case` clauses. But there is something strange. {{{ $ cat RedundantCase.hs main :: IO () main = do case 0::Int of 0 -> putStrLn "A" 1 -> putStrLn "B" _ -> putStrLn "C" case 0::Int of 0 -> putStrLn "A" 1 -> putStrLn "B" 2 -> putStrLn "C" case 0::Integer of 0 -> putStrLn "A" 1 -> putStrLn "B" _ -> putStrLn "C" case 0::Integer of 0 -> putStrLn "A" 1 -> putStrLn "B" 2 -> putStrLn "C" case 0::Integer of 1 -> putStrLn "B" 2 -> putStrLn "C" let dummy :: Integer dummy = 0 case dummy of 0 -> putStrLn "A" 1 -> putStrLn "B" _ -> putStrLn "C" case "foo" of "foo" -> putStrLn "A" "bar" -> putStrLn "B" "baz" -> putStrLn "C" if True then putStrLn "X" else putStrLn "Y" }}} {{{ $ ghc-8.2.2 -Wall RedundantCase.hs [1 of 1] Compiling Main ( RedundantCase.hs, RedundantCase.o ) RedundantCase.hs:4:7: warning: [-Woverlapping-patterns] Pattern match is redundant In a case alternative: 0 -> ... | 4 | 0 -> putStrLn "A" | ^^^^^^^^^^^^^^^^^ RedundantCase.hs:5:7: warning: [-Woverlapping-patterns] Pattern match is redundant In a case alternative: 1 -> ... | 5 | 1 -> putStrLn "B" | ^^^^^^^^^^^^^^^^^ RedundantCase.hs:8:4: warning: [-Wincomplete-patterns] Pattern match(es) are non-exhaustive In a case alternative: Patterns not matched: 0 | 8 | case 0::Int of | ^^^^^^^^^^^^^^... RedundantCase.hs:9:7: warning: [-Woverlapping-patterns] Pattern match is redundant In a case alternative: 0 -> ... | 9 | 0 -> putStrLn "A" | ^^^^^^^^^^^^^^^^^ RedundantCase.hs:10:7: warning: [-Woverlapping-patterns] Pattern match is redundant In a case alternative: 1 -> ... | 10 | 1 -> putStrLn "B" | ^^^^^^^^^^^^^^^^^ RedundantCase.hs:11:7: warning: [-Woverlapping-patterns] Pattern match is redundant In a case alternative: 2 -> ... | 11 | 2 -> putStrLn "C" | ^^^^^^^^^^^^^^^^^ RedundantCase.hs:15:7: warning: [-Woverlapping-patterns] Pattern match is redundant In a case alternative: 1 -> ... | 15 | 1 -> putStrLn "B" | ^^^^^^^^^^^^^^^^^ RedundantCase.hs:16:7: warning: [-Woverlapping-patterns] Pattern match is redundant In a case alternative: _ -> ... | 16 | _ -> putStrLn "C" | ^^^^^^^^^^^^^^^^^ RedundantCase.hs:20:7: warning: [-Woverlapping-patterns] Pattern match is redundant In a case alternative: 1 -> ... | 20 | 1 -> putStrLn "B" | ^^^^^^^^^^^^^^^^^ RedundantCase.hs:21:7: warning: [-Woverlapping-patterns] Pattern match is redundant In a case alternative: 2 -> ... | 21 | 2 -> putStrLn "C" | ^^^^^^^^^^^^^^^^^ RedundantCase.hs:23:4: warning: [-Wincomplete-patterns] Pattern match(es) are non-exhaustive In a case alternative: Patterns not matched: 0 | 23 | case 0::Integer of | ^^^^^^^^^^^^^^^^^^... RedundantCase.hs:24:7: warning: [-Woverlapping-patterns] Pattern match is redundant In a case alternative: 1 -> ... | 24 | 1 -> putStrLn "B" | ^^^^^^^^^^^^^^^^^ RedundantCase.hs:25:7: warning: [-Woverlapping-patterns] Pattern match is redundant In a case alternative: 2 -> ... | 25 | 2 -> putStrLn "C" | ^^^^^^^^^^^^^^^^^ RedundantCase.hs:34:4: warning: [-Wincomplete-patterns] Pattern match(es) are non-exhaustive In a case alternative: Patterns not matched: [] (p:_) where p is not one of {'b', 'f'} ['b'] ('b':p:_) where p is not one of {'a'} ... | 34 | case "foo" of | ^^^^^^^^^^^^^... Linking RedundantCase ... }}} In the first case it warns about the wrong patterns, in the second case it warns about all patterns and a non-exhaustive pattern list. In the following three cases using `Integer` the warnings seem to be correct. The next case shows that I can suppress the warning if I hide the constant nature of the case selector a bit. Then a case on a `String` - GHC does not seem to try to detect redundant pattern matches but falls back to a general test on exhaustive pattern lists. Finally, in a constant `case` on `Bool` I can avoid the warning using a plain `if-then-else`. Now I wonder what the purpose of the warning is at all. First I thought that it wants to warn me, that the patterns overlap, i.e. pattern `_` contains the already handled case `0`. This does not seem to be the purpose of the warning - and such overlapping patterns are pretty common, aren't they? Second thought: GHC wants to warn me about redundant patterns in the presence of a constant case selector. But then, it does so with varying degrees of success: For `Integer` it works, but not for `Int` or `String`. Is it really only about constant case selectors? Then, not only some pattern matches are redundant but the whole `case` clause is redundant. Then again, can't we assume that the programmer wrote such a `case` clause by intend? At least, this is how I use a `case` clause with constant selector: as a type-safe way to out-comment alternative implementations. Thus my question: Where is this warning useful? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14546> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9247: Document -XDatatypeContexts in flag reference
by GHC 03 Jun '18

03 Jun '18

#9247: Document -XDatatypeContexts in flag reference ------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire Type: bug | Status: new Priority: low | Milestone: Component: Documentation | 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: | ------------------------------------+------------------------------------- It may be a deprecated feature, but it still exists and should be listed. I can do this. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9247> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11066: Inacessible branch should be warning - otherwise breaks type soundness?
by GHC 03 Jun '18

03 Jun '18

#11066: Inacessible branch should be warning - otherwise breaks type soundness? -------------------------------------+------------------------------------- Reporter: rrnewton | Owner: Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- GHC 7.10.2 reports inaccessible branches as a type error, and I think this is really a bug. First, the implicit thinking seems to be "why would a user want to write inaccessible cases, they'd be crazy!". But that only applies to human-written code. Program generators can have a great deal of trouble avoiding this error, unless they replicate the GHC type checker to predict the problem and prune branches. (That's why we are hitting this error and are stuck.) Second, it seems like this is a problem for type soundness. See the attached program where "step1" typechecks but "step2" does not. And yet, the operational semantics should allow step1 to reduce to step2. Indeed, in the "GADTs meet their match" paper it seems like the intent was to warn for these inaccessible cases, not error. For example, the paper contains the language: "If we warn that a right-hand side of a non-redundant clause is inaccessible," -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11066> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14059: COMPLETE sets don't work at all with data family instances
by GHC 03 Jun '18

03 Jun '18

#14059: COMPLETE sets don't work at all with data family instances -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple PatternSynonyms, | PatternMatchWarnings | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Here's some code that uses a pattern synonym for a data family GADT constructor, along with a corresponding `COMPLETE` set: {{{#!hs {-# LANGUAGE GADTs #-} {-# LANGUAGE PatternSynonyms #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeInType #-} {-# LANGUAGE TypeOperators #-} {-# OPTIONS_GHC -Wincomplete-patterns #-} module Bug where data family Sing (a :: k) data instance Sing (z :: Bool) where SFalse :: Sing False STrue :: Sing True pattern STooGoodToBeTrue :: forall (z :: Bool). () => z ~ True => Sing z pattern STooGoodToBeTrue = STrue {-# COMPLETE SFalse, STooGoodToBeTrue #-} wibble :: Sing (z :: Bool) -> Bool wibble STrue = True wobble :: Sing (z :: Bool) -> Bool wobble STooGoodToBeTrue = True }}} However, if you compile this, you might be surprised to find out that GHC only warns about `wibble` being non-exhaustive: {{{ $ ghci Bug.hs GHCi, version 8.2.1: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted ) Bug.hs:23:1: warning: [-Wincomplete-patterns] Pattern match(es) are non-exhaustive In an equation for ‘wibble’: Patterns not matched: SFalse | 23 | wibble STrue = True | ^^^^^^^^^^^^^^^^^^^ }}} I believe the use of data families is the culprit here, since a variant of this program which doesn't use data families correctly warns for both `wibble` and `wobble`: {{{#!hs {-# LANGUAGE GADTs #-} {-# LANGUAGE PatternSynonyms #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeInType #-} {-# LANGUAGE TypeOperators #-} {-# OPTIONS_GHC -Wincomplete-patterns #-} module Foo where data SBool (z :: Bool) where SFalse :: SBool False STrue :: SBool True pattern STooGoodToBeTrue :: forall (z :: Bool). () => z ~ True => SBool z pattern STooGoodToBeTrue = STrue {-# COMPLETE SFalse, STooGoodToBeTrue #-} wibble :: SBool z -> Bool wibble STrue = True wobble :: SBool z -> Bool wobble STooGoodToBeTrue = True }}} {{{ $ ghci Foo.hs GHCi, version 8.2.1: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Foo ( Foo.hs, interpreted ) Foo.hs:20:1: warning: [-Wincomplete-patterns] Pattern match(es) are non-exhaustive In an equation for ‘wibble’: Patterns not matched: SFalse | 20 | wibble STrue = True | ^^^^^^^^^^^^^^^^^^^ Foo.hs:23:1: warning: [-Wincomplete-patterns] Pattern match(es) are non-exhaustive In an equation for ‘wobble’: Patterns not matched: SFalse | 23 | wobble STooGoodToBeTrue = True | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14059> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13777: Poor error message around CUSKs
by GHC 02 Jun '18

02 Jun '18

#13777: Poor error message around CUSKs -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1-rc2 Keywords: TypeInType, | Operating System: Unknown/Multiple CUSKs | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- While typing up comment:7:ticket:13761, I came across a poor error message around CUSKs. {{{ data Proxy (a :: k) = P data S :: forall k. Proxy k -> Type where MkS :: S (P :: Proxy Maybe) }}} produces {{{ You have written a *complete user-suppled kind signature*, but the following variable is undetermined: k0 :: * Perhaps add a kind signature. Inferred kinds of user-written variables: }}} That promised list of the kinds of user-written variables is empty. Either GHC should find something to print (like `k :: k0`, perhaps) or omit the header. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13777> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14324: Consider deprecating STM invariant mechanism
by GHC 02 Jun '18

02 Jun '18

#14324: Consider deprecating STM invariant mechanism -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: task | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- fryguybob and I were recently discussing the STM invariant mechanism. This mechanism is, presumably, intended to expose problems from odd interleavings of transactions. However, fryguybob pointed out that the implementation currently takes so many locks that it very likely prevents these odd interleavings from occurring. In addition, * the implementation doesn't handle nested STM invariants correctly (#7930) * the locking behavior of the implementation was, until very recently, utterly wrong (#14310) * the feature introduces quite a bit of complexity in the RTS * the interface has essentially no users, as evidenced by a Hackage search and the fact that #14310 went unnoticed for years All of this raises the question: Is the STM invariants feature really where we want to spend our complexity budget? Perhaps it is time for this feature to quietly pass (after an appropriate deprecation period, of course). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14324> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14310: Assertion triggered by STM invariant.
by GHC 02 Jun '18

02 Jun '18

#14310: Assertion triggered by STM invariant. --------------------------------------+---------------------------------- Reporter: mbw | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Linux Architecture: x86_64 (amd64) | Type of failure: Runtime crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+---------------------------------- The program attached depends on the async and stm packages. It will push some numbers through a pipeline, while keeping track of some state. If invoked without arguments, the program will output the state and result of each iteration. If invoked via "./repro check", an STM invariant will be installed when the state is initialized. This invariant will cause the program to a) hangup, presumably due to a livelock, if the program has been compiled without "-debug", b) crash with the following error: "internal error: ASSERTION FAILED: file rts/RaiseAsync.c, line 1001", if the "-debug" flag has been used for compilation. The latter case also happens with GHC 8.0.2: "internal error: ASSERTION FAILED: file rts/RaiseAsync.c, line 997". Furthermore, this problem only occurs if the program is compiled using the additional flags "-rtsopts -threaded -with-rtsopts=-N". -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14310> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12939: ghc-8.0.1.20161117 did not install ghc.1 manpage
by GHC 02 Jun '18

02 Jun '18

#12939: ghc-8.0.1.20161117 did not install ghc.1 manpage ----------------------------------------+--------------------------------- Reporter: juhpetersen | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.2 Component: Build System | Version: 8.0.2-rc1 Keywords: | Operating System: Linux Architecture: Unknown/Multiple | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+--------------------------------- This seems to be a build regression from ghc-8.0.1. The ghc.1 manpage was not installed for the 8.0.2 RC1 build. I reported this in mail earlier and unfortunately in the meantime lost the buildlogs on Fedora Copr, but since the upstream binary tarballs for Linux also don't seem to contain ghc.1 either it should not be too hard to reproduce. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12939> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13426: compile-time memory-usage regression for DynFlags between GHC 8.0 and GHC 8.2
by GHC 01 Jun '18

01 Jun '18

#13426: compile-time memory-usage regression for DynFlags between GHC 8.0 and GHC 8.2 -------------------------------------+------------------------------------- Reporter: hvr | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 8.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I notice that buildbots were having a hard-time building GHC 8.2 snapshots... so I investigated... One thing that jumped at me was the memory usage while compiling DynFlags which is the worst memory-offender with 4777MiB of resident size: {{{ "inplace/bin/ghc-stage1" -hisuf hi -osuf o -hcsuf hc -static -H32m -O -Wall -Iincludes -Iincludes/dist -Iincludes/dist-derivedconstants/header -Iincludes/dist-ghcconstants/header -this-unit-id ghc-8.2.0.201 70313 -hide-all-packages -i -icompiler/backpack -icompiler/basicTypes -icompiler/cmm -icompiler/codeGen -icompiler/coreSyn -icompiler/deSugar -icompiler/ghci -icompiler/hsSyn -icompiler/iface -icompiler/llvmGen - icompiler/main -icompiler/nativeGen -icompiler/parser -icompiler/prelude -icompiler/profiling -icompiler/rename -icompiler/simplCore -icompiler/simplStg -icompiler/specialise -icompiler/stgSyn -icompiler/stranal -icompiler/typecheck -icompiler/types -icompiler/utils -icompiler/vectorise -icompiler/stage2/build -Icompiler/stage2/build -icompiler/stage2/build/./autogen -Icompiler/stage2/build/./autogen -Icompiler/. -Icompi ler/parser -Icompiler/utils -Icompiler/../rts/dist/build -Icompiler/stage2 -optP-DGHCI -optP-include -optPcompiler/stage2/build/./autogen/cabal_macros.h -package-id base-4.10.0.0 -package-id deepseq-1.4.3.0 -pa ckage-id directory-1.3.0.2 -package-id process-1.4.3.0 -package-id bytestring-0.10.8.2 -package-id binary-0.8.4.1 -package-id time-1.8.0.1 -package-id containers-0.5.10.2 -package-id array-0.5.1.2 -package-id fil epath-1.4.1.1 -package-id template-haskell-2.12.0.0 -package-id hpc-0.6.0.3 -package-id transformers-0.5.2.0 -package-id ghc- boot-8.2.0.20170313 -package-id ghc-boot-th-8.2.0.20170313 -package-id ghci-8.2.0.20170 313 -package-id hoopl-3.10.2.2 -package-id unix-2.7.2.1 -package-id terminfo-0.4.0.2 -Wall -fno-warn-name-shadowing -this-unit-id ghc -XHaskell2010 -optc-DTHREADED_RTS -DGHCI_TABLES_NEXT_TO_CODE -DSTAGE=2 -Rghc-t iming -O2 -no-user-package-db -rtsopts -Wnoncanonical-monad- instances -odir compiler/stage2/build -hidir compiler/stage2/build -stubdir compiler/stage2/build -dynamic-too -c compiler/main/DynFlags.hs -o compiler/stage2/build/DynFlags.o -dyno compiler/stage2/build/DynFlags.dyn_o }}} {{{ <<ghc: 63014533832 bytes, 4032 GCs, 395131448/1973969928 avg/max bytes residency (24 samples), 4777M in use, 0.000 INIT (0.000 elapsed), 32.207 MUT (33.221 elapsed), 26.682 GC (26.685 elapsed) :ghc>> }}} Then I did two clean full builds of the `ghc-8.0` and `ghc-8.2` branch, and collected the -Rghc-timings output into simple 3-columns .csv files; Here's are the respective top-12 entries for GHC 8.0 and GHC 8.2 respectively: {{{#!bash $ sort -t, -k2n build.80.csv | tail -n12 "inplace/bin/ghc-stage1",560,compiler/stage2/build/TcRnDriver.o "inplace/bin/ghc-stage1",572,compiler/stage2/build/TcRnDriver.p_o "inplace/bin/ghc-stage1",572,compiler/stage2/build/TcSplice.o "inplace/bin/ghc-stage1",847,compiler/stage2/build/OptCoercion.p_o "/opt/ghc/bin/ghc",979,compiler/stage1/build/OptCoercion.o "/opt/ghc/bin/ghc",1036,compiler/stage1/build/DynFlags.o "/opt/ghc/bin/ghc",1040,compiler/stage1/build/X86/CodeGen.o "inplace/bin/ghc-stage1",1119,compiler/stage2/build/DynFlags.p_o "inplace/bin/ghc-stage1",1123,compiler/stage2/build/DynFlags.o "inplace/bin/ghc-stage1",1178,compiler/stage2/build/OptCoercion.o "inplace/bin/ghc-stage1",1233,compiler/stage2/build/X86/CodeGen.o "inplace/bin/ghc-stage1",1282,compiler/stage2/build/X86/CodeGen.p_o }}} {{{#!bash $ sort -t, -k2n build.82.csv | tail -n12 "inplace/bin/ghc-stage1",891,compiler/stage2/build/CmmParse.p_o "/opt/ghc/bin/ghc",1053,compiler/stage1/build/DynFlags.o "/opt/ghc/bin/ghc",1058,compiler/stage1/build/OptCoercion.o "inplace/bin/ghc-stage1",1284,compiler/stage2/build/HsExpr.p_o "inplace/bin/ghc-stage1",1313,compiler/stage2/build/HsExpr.o "/opt/ghc/bin/ghc",1394,compiler/stage1/build/X86/CodeGen.o "inplace/bin/ghc-stage1",1495,compiler/stage2/build/X86/CodeGen.o "inplace/bin/ghc-stage1",1605,compiler/stage2/build/X86/CodeGen.p_o "inplace/bin/ghc-stage1",1620,compiler/stage2/build/OptCoercion.o "inplace/bin/ghc-stage1",1733,compiler/stage2/build/OptCoercion.p_o "inplace/bin/ghc-stage1",3989,compiler/stage2/build/DynFlags.p_o "inplace/bin/ghc-stage1",4777,compiler/stage2/build/DynFlags.o }}} What's apparent from this data: - GHC stage0 (which was GHC 8.0.2) is able to build DynFlags.o for GHC 8.0 and GHC 8.2 w/ roughtly the same amount of max resident memory, i.e. 1 GiB - **GHC 8.2 stage1 however needs 4 times the amount of memory more than GHC 8.0 to build the same `DynFlags.hs` module!** -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13426> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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