April 2015 - ghc-tickets

[GHC] #8123: GHCi warns about -eventlog even though it's sometimes necessary
by GHC 20 Jul '15

20 Jul '15

#8123: GHCi warns about -eventlog even though it's sometimes necessary -------------------------+------------------------------------------------- Reporter: akio | Owner: Type: bug | Status: new Priority: | Milestone: normal | Version: 7.6.3 Component: GHCi | Operating System: Linux Keywords: | Type of failure: Incorrect warning at Architecture: | compile-time x86_64 (amd64) | Test Case: Difficulty: | Blocking: Unknown | Blocked By: | Related Tickets: | -------------------------+------------------------------------------------- If I invoke GHCi as {{{ghci -eventlog}}}, it says: {{{Warning: -debug, -threaded and -ticky are ignored by GHCi}}}. However, the flag does make a difference, in that GHCi will be able to load object files that were compiled using {{{-eventlog}}}. For this reason, I don't think {{{-eventlog}}} should trigger the warning. Also runghc has the same issue. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8123> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10224: Partial type signatures generate typed hole warnings
by GHC 18 Jul '15

18 Jul '15

#10224: Partial type signatures generate typed hole warnings -------------------------------------+------------------------------------- Reporter: quchen | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.10.2 Component: Compiler | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect Unknown/Multiple | warning at compile-time Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- GHCi generates typed hole warnings in type signatures even when PartialTypeSignatures is enabled: {{{ > :set -XPartialTypeSignatures > :t (==) :: Char -> _ <interactive>:1:17: Warning: Found hole ‘_’ with type: Char -> Bool In an expression type signature: Char -> _ In the expression: (==) :: Char -> _ (==) :: Char -> _ :: Char -> Char -> Bool > :set -XNoPartialTypeSignatures > :t (==) :: Char -> _ <interactive>:1:17: Found hole ‘_’ with type: Char -> Bool To use the inferred type, enable PartialTypeSignatures In an expression type signature: Char -> _ In the expression: (==) :: Char -> _ }}} Similarly, GHC 7.10.1, when given the following source, {{{ {-# LANGUAGE PartialTypeSignatures #-} f = (==) :: Char -> _ main = return () }}} mentions that it "found a hole". -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10224> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9243: Recompilation avoidance works imperfectly with -fno-code/-fwrite-interface
by GHC 18 Jul '15

18 Jul '15

#9243: Recompilation avoidance works imperfectly with -fno-code/-fwrite-interface -------------------------+------------------------------------------------- Reporter: | Owner: ezyang | Status: new Type: bug | Milestone: Priority: | Version: 7.9 normal | Operating System: Unknown/Multiple Component: | Type of failure: Compile-time performance bug Compiler | Test Case: Keywords: | Blocking: Architecture: | Unknown/Multiple | Difficulty: | Unknown | Blocked By: | Related Tickets: | -------------------------+------------------------------------------------- With the latest `-fwrite-interface` enhancements, a build directory can contain interface files independently of object files. In cases like this, we would like to have recompilation avoidance avoid typechecking files whose interface files are up-to-date. However, this does not currently work: we always re-typecheck: {{{ t-edyang@cam-05-unx:/5playpen/t-edyang/sandbox/q$ /5playpen/t-edyang/ghc- backpack/inplace/bin/ghc-stage2 --make A.hs -fno-code -fwrite-interface [1 of 1] Compiling A ( A.hs, nothing ) t-edyang@cam-05-unx:/5playpen/t-edyang/sandbox/q$ /5playpen/t-edyang/ghc- backpack/inplace/bin/ghc-stage2 --make A.hs -fno-code -fwrite-interface [1 of 1] Compiling A ( A.hs, nothing ) }}} The reason for this is that recompilation avoidance logic in `compileOne` (in `DriverPipeline.hs`) seems to rely exclusively on "linkables" in order to figure out if source has been modified or not. We never generate an object file with `-fwrite-interface`, so the compiler always concludes that we need to retypecheck. However, recompilation avoidance for hs-boot does work. The reason for this is because we create a dummy o-boot linkable. We can't use this strategy for `-fno-code`, because the dummy object file would imply that we actually compiled the file (which we didn't). The upshot is that to fix this problem, it looks like we might have to rejigger all of the logic in `compileOne`, which why I gave up on this for now. Related to https://github.com/haskell/cabal/issues/1179 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9243> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9618: Undocument ImpredicativeTypes
by GHC 17 Jul '15

17 Jul '15

#9618: Undocument ImpredicativeTypes -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Documentation | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Easy (less than 1 | Type of failure: hour) | None/Unknown Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- I understand that Simon Peyton Jones intends to make `ImpredicativeTypes` work some day, but it doesn't work now. I think the thing to do for now is to remove it from the user manual. It can be put back in later if it's ever fixed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9618> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10226: Regression in constraint solver from 7.8 to 7.10
by GHC 13 Jul '15

13 Jul '15

#10226: Regression in constraint solver from 7.8 to 7.10 -------------------------------------+------------------------------------- Reporter: edsko | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 (Type checker) | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Best explained by example: {{{#!hs {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE AllowAmbiguousTypes #-} -- only necessary in 7.10 {-# LANGUAGE FlexibleContexts #-} -- necessary for showFromF' example type family F a type family FInv a -- This definition is accepted in 7.8 without anything extra, but requires -- AllowAmbiguousTypes in 7.10 (this, by itself, is not a problem): showFromF :: (Show a, FInv (F a) ~ a) => F a -> String showFromF fa = undefined -- Consider what happens when we attempt to call `showFromF` at some type b. -- In order to check that this is valid, we have to find an a such that -- -- > b ~ F a /\ Show a /\ FInv (F a) ~ a -- -- Introducing an intermeidate variable `x` for the result of `F a` gives us -- -- > b ~ F a /\ Show a /\ FInv x ~ a /\ F a ~ x -- -- Simplifying -- -- > b ~ x /\ Show a /\ FInv x ~ a /\ F a ~ x -- -- Set x := b -- -- > Show a /\ FInv b ~ a /\ F a ~ b -- -- Set a := FInv b -- -- > Show (FInv b) /\ FInv b ~ FInv b /\ F (FInv b) ~ b -- -- Simplifying -- -- > Show (FInv b) /\ F (FInv b) ~ b -- -- Indeed, we can give this definition in 7.8, but not in 7.10: showFromF' :: (Show (FInv b), F (FInv b) ~ b) => b -> String showFromF' = showFromF {------------------------------------------------------------------------------- In 7.10 the definition of showFromF' is not accepted, but it gets stranger. In 7.10 we cannot _call_ showFromF at all all, even at a concrete type. Below we try to call it at type b ~ Int. It would need to show > Show (FInv Int) /\ F (FInt Int) ~ Int all of which should easily get resolved, but somehow don't. -------------------------------------------------------------------------------} type instance F Int = Int type instance FInv Int = Int test :: String test = showFromF (0 :: Int) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10226> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10009: type inference regression when faking injective type families
by GHC 13 Jul '15

13 Jul '15

#10009: type inference regression when faking injective type families -------------------------------------+------------------------------------- Reporter: aavogt | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1-rc1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- ghc-7.10.0.20141222 does not accept the program unless I uncomment the type signature (a :: a). ghc-7.8 accepts it as-is. {{{#!hs {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeFamilies #-} class (UnF (F a) ~ a, Show a) => C a where type F a f :: F a -> a type family UnF a g :: forall a. C a => a -> String g _ = show a where a = f (undefined :: F a) -- :: a }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10009> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8709: `make 1` does not work (well)
by GHC 11 Jul '15

11 Jul '15

#8709: `make 1` does not work (well) ------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Build System | 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: | ------------------------------------+------------------------------------- Say I do a `sync-all pull` and then fix a bunch of merge errors. The changes mean that I need to recompile the stage-1 compiler. So, I dutifully `make distclean` and start rebuilding. I then find a bunch of compiler errors in my edited code. Now, I'd like to start the fix error/recompile loop. BUT, when I do `make 1` in the `compiler/` directory, I get errors: {{{ rae:13:49:29 ~/Documents/ghc/compiler> make 1 make -C .. stage=1 all_ghc_stage1 compiler_dist_NO_BUILD_DEPS=YES compiler_dist-boot_NO_BUILD_DEPS=YES compiler_dist- install_NO_BUILD_DEPS=YES NO_GENERATED_MAKEFILE_RULES=YES OMIT_PHASE_0=YES OMIT_PHASE_1=YES compiler_stage1_NO_BUILD_DEPS=YES compiler_stage2_NO_BUILD_DEPS=YES compiler_stage3_NO_BUILD_DEPS=YES ghc_stage1_NO_BUILD_DEPS=YES ghc_stage2_NO_BUILD_DEPS=YES ghc_stage3_NO_BUILD_DEPS=YES ONLY_DEPS_FOR="compiler_stage1 ghc_stage1" ===--- building final phase make -r --no-print-directory -f ghc.mk phase=final all_ghc_stage1 libraries/old-time/ghc.mk:5: libraries/old-time/dist-install/package- data.mk: No such file or directory libraries/haskell98/ghc.mk:5: libraries/haskell98/dist-install/package- data.mk: No such file or directory libraries/haskell2010/ghc.mk:5: libraries/haskell2010/dist-install /package-data.mk: No such file or directory libraries/random/ghc.mk:5: libraries/random/dist-install/package-data.mk: No such file or directory libraries/primitive/ghc.mk:5: libraries/primitive/dist-install/package- data.mk: No such file or directory libraries/vector/ghc.mk:5: libraries/vector/dist-install/package-data.mk: No such file or directory libraries/dph/dph-base/ghc.mk:5: libraries/dph/dph-base/dist-install /package-data.mk: No such file or directory libraries/dph/dph-prim-interface/ghc.mk:5: libraries/dph/dph-prim- interface/dist-install/package-data.mk: No such file or directory libraries/dph/dph-prim-seq/ghc.mk:5: libraries/dph/dph-prim-seq/dist- install/package-data.mk: No such file or directory libraries/dph/dph-prim-par/ghc.mk:5: libraries/dph/dph-prim-par/dist- install/package-data.mk: No such file or directory libraries/dph/dph-lifted-base/ghc.mk:5: libraries/dph/dph-lifted-base /dist-install/package-data.mk: No such file or directory libraries/dph/dph-lifted-boxed/ghc.mk:5: libraries/dph/dph-lifted-boxed /dist-install/package-data.mk: No such file or directory libraries/dph/dph-lifted-copy/ghc.mk:5: libraries/dph/dph-lifted-copy /dist-install/package-data.mk: No such file or directory libraries/dph/dph-lifted-vseg/ghc.mk:5: libraries/dph/dph-lifted-vseg /dist-install/package-data.mk: No such file or directory libraries/ghc-prim/ghc.mk:4: libraries/ghc-prim/dist-install/package- data.mk: No such file or directory libraries/integer-gmp/ghc.mk:4: libraries/integer-gmp/dist-install /package-data.mk: No such file or directory libraries/base/ghc.mk:4: libraries/base/dist-install/package-data.mk: No such file or directory libraries/filepath/ghc.mk:4: libraries/filepath/dist-install/package- data.mk: No such file or directory libraries/array/ghc.mk:4: libraries/array/dist-install/package-data.mk: No such file or directory libraries/deepseq/ghc.mk:4: libraries/deepseq/dist-install/package- data.mk: No such file or directory libraries/bytestring/ghc.mk:4: libraries/bytestring/dist-install/package- data.mk: No such file or directory libraries/containers/ghc.mk:4: libraries/containers/dist-install/package- data.mk: No such file or directory libraries/old-locale/ghc.mk:4: libraries/old-locale/dist-install/package- data.mk: No such file or directory libraries/time/ghc.mk:4: libraries/time/dist-install/package-data.mk: No such file or directory libraries/unix/ghc.mk:4: libraries/unix/dist-install/package-data.mk: No such file or directory libraries/directory/ghc.mk:4: libraries/directory/dist-install/package- data.mk: No such file or directory libraries/process/ghc.mk:4: libraries/process/dist-install/package- data.mk: No such file or directory libraries/hpc/ghc.mk:4: libraries/hpc/dist-install/package-data.mk: No such file or directory libraries/pretty/ghc.mk:4: libraries/pretty/dist-install/package-data.mk: No such file or directory libraries/template-haskell/ghc.mk:4: libraries/template-haskell/dist- install/package-data.mk: No such file or directory libraries/Cabal/Cabal/ghc.mk:4: libraries/Cabal/Cabal/dist-install /package-data.mk: No such file or directory libraries/binary/ghc.mk:4: libraries/binary/dist-install/package-data.mk: No such file or directory libraries/bin-package-db/ghc.mk:4: libraries/bin-package-db/dist-install /package-data.mk: No such file or directory libraries/hoopl/ghc.mk:4: libraries/hoopl/dist-install/package-data.mk: No such file or directory libraries/transformers/ghc.mk:4: libraries/transformers/dist-install /package-data.mk: No such file or directory libraries/xhtml/ghc.mk:4: libraries/xhtml/dist-install/package-data.mk: No such file or directory libraries/terminfo/ghc.mk:4: libraries/terminfo/dist-install/package- data.mk: No such file or directory libraries/haskeline/ghc.mk:4: libraries/haskeline/dist-install/package- data.mk: No such file or directory libraries/integer-gmp/gmp/ghc.mk:49: libraries/integer-gmp/gmp/config.mk: No such file or directory utils/hsc2hs/ghc.mk:16: utils/hsc2hs/dist-install/package-data.mk: No such file or directory utils/ghc-pkg/ghc.mk:66: utils/ghc-pkg/dist-install/package-data.mk: No such file or directory utils/dll-split/ghc.mk:18: utils/dll-split/dist-install/package-data.mk: No such file or directory utils/ghc-pwd/ghc.mk:8: utils/ghc-pwd/dist-install/package-data.mk: No such file or directory utils/ghc-cabal/ghc.mk:67: utils/ghc-cabal/dist-install/package-data.mk: No such file or directory utils/hpc/ghc.mk:18: utils/hpc/dist-install/package-data.mk: No such file or directory utils/runghc/ghc.mk:28: utils/runghc/dist-install/package-data.mk: No such file or directory utils/mkUserGuidePart/ghc.mk:18: utils/mkUserGuidePart/dist/package- data.mk: No such file or directory utils/compare_sizes/ghc.mk:8: utils/compare_sizes/dist-install/package- data.mk: No such file or directory make[2]: *** No rule to make target `libraries/integer-gmp/gmp/config.mk'. Stop. make[1]: *** [all_ghc_stage1] Error 2 make: *** [1] Error 2 }}} Using `make stage=1` works fine, but computing the dependencies each time is annoying. In past experience, I've seen that, once the stage-1 compiler builds to completion at least once, `make 1` works just fine -- it just fails after a `clean`. I don't recall having this problem with `make 2`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8709> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10298: Infinite loop when shared libraries are unavailable
by GHC 10 Jul '15

10 Jul '15

#10298: Infinite loop when shared libraries are unavailable -------------------------------------+------------------------------------- Reporter: snoyberg | Owner: simonmar Type: bug | Status: new Priority: normal | Milestone: Component: Runtime | Version: 7.10.1 System | Operating System: Linux Keywords: | Type of failure: Runtime crash Architecture: x86_64 | Blocked By: (amd64) | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Originally discussed at: https://groups.google.com/d/msg/haskell- cafe/5ZTv5mCG_HI/hBJ-VkdpxdoJ. Note that this was originally discussed as a static linking and Docker issue, but in fact affects dynamically linked executables without any containerization. I've put together the following script that reproduces my problem: {{{ cat > hello.hs <<EOF main :: IO () main = putStrLn "Hello World" EOF ghc hello.hs rm -rf tmp mkdir tmp cp hello tmp mkdir -p tmp/usr/lib/x86_64-linux-gnu cp /usr/lib/x86_64-linux-gnu/libgmp.so.10 tmp/usr/lib/x86_64-linux-gnu mkdir -p tmp/lib/x86_64-linux-gnu cp \ /lib/x86_64-linux-gnu/libm.so.6 \ /lib/x86_64-linux-gnu/librt.so.1 \ /lib/x86_64-linux-gnu/libdl.so.2 \ /lib/x86_64-linux-gnu/libc.so.6 \ /lib/x86_64-linux-gnu/libpthread.so.0 \ tmp/lib/x86_64-linux-gnu mkdir -p tmp/lib64 cp /lib64/ld-linux-x86-64.so.2 tmp/lib64 #mkdir -p tmp/usr/lib/x86_64-linux-gnu/gconv/ #cp \ # /usr/lib/x86_64-linux-gnu/gconv/UTF-32.so \ # /usr/lib/x86_64-linux-gnu/gconv/gconv-modules \ # tmp/usr/lib/x86_64-linux-gnu/gconv sudo chroot tmp /hello }}} If I uncomment the block that copies the gconv files, the program runs as expected. However, without those files copied, the program burns CPU and consumes memory until killed by the OS. I ran strace on a similar executable, and got the results at: https://gist.github.com/snoyberg/095efb17e36acc1d6360 Note that this problem also occurs with statically linked executables when some of the other dynamically linked libraries are not available in the chroot environment. Expected behavior: ideal would be not to require the gconv files and other shared libraries be present, especially when statically linked. Barring that, it would be much better if the RTS could produce a meaningful error message about the missing file. Note that strace does demonstrate that a open system call is failing, e.g.: open("/usr/lib/x86_64-linux-gnu/gconv/gconv-modules.cache", O_RDONLY) = -1 ENOENT (No such file or directory) Reproduced on GHC 7.8.4 and 7.10.1, on Ubuntu 14.04 64-bit. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10298> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10351: Inferred type is rejected
by GHC 09 Jul '15

09 Jul '15

#10351: Inferred type is rejected -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Consider {{{ class C a where op :: a -> () f x = op [x] }}} we get {{{ Foo.hs:14:1: error: Non type-variable argument in the constraint: C [t] (Use FlexibleContexts to permit this) When checking that ‘f’ has the inferred type f :: forall t. C [t] => t -> () }}} Arguably, if `FlexibleContexts` is not on, we should not infer a type that will immediately be rejected. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10351> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9665: Add "since" information to LANGUAGE extensions in GHC user guide
by GHC 07 Jul '15

07 Jul '15

#9665: Add "since" information to LANGUAGE extensions in GHC user guide -------------------------------------+------------------------------------- Reporter: andreas.abel | Owner: Type: task | Status: new Priority: high | Milestone: Component: Documentation | Version: 7.9 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- If one wants to support older versions of GHC, it is hard to find out whether one can use a certain LANGUAGE extension. One has to go to older versions of the GHC manual to find out whether the corresponding documentation was already there, or browse release notes. Requests: 1. Document for new LANGUAGE extensions that they are available since version 7.10. For example, by adding "(Since GHC 7.10)" to the heading of the new feature. 2. Do this also for the previous LANGUAGE extensions, by adding e.g., "(Since GHC 7.6)" etc. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9665> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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