February 2015 - ghc-tickets

[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 10 Jul '15

10 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] #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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[GHC] #10023: Relax Monad constraint in traceM and traceShowM to Applicative
by GHC 07 Jul '15

07 Jul '15

#10023: Relax Monad constraint in traceM and traceShowM to Applicative -------------------------------------+------------------------------------- Reporter: | Owner: RyanGlScott | Status: new Type: feature | Milestone: request | Version: 7.10.1-rc1 Priority: normal | Operating System: Unknown/Multiple Component: | Type of failure: Other libraries/base | Blocked By: Keywords: | Related Tickets: Architecture: | Unknown/Multiple | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Now that {{{Applicative}}} is a superclass of {{{Monad}}} in GHC 7.10, the current type signatures of {{{traceM}}} and {{{traceShowM}}} from {{{Debug.Trace}}} are too constricted: {{{#!hs traceM :: Monad m => String -> m () traceM string = trace string $ return () traceShowM :: (Show a, Monad m) => a -> m () traceShowM = traceM . show }}} These can be equivalently defined with {{{Applicative}}}: {{{#!hs traceM :: Applicative m => String -> m () traceM string = trace string $ pure () traceShowM :: (Show a, Applicative m) => a -> m () traceShowM = traceM . show }}} However, the {{{M}}} suffixes probably won't make sense after changing the type signatures, so it might be wise to create new {{{traceA}}} and {{{traceShowA}}} functions and deprecate {{{traceM}}} and {{{traceShowM}}}. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10023> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9863: Provide PowerPC 64 bit native code generator
by GHC 07 Jul '15

07 Jul '15

#9863: Provide PowerPC 64 bit native code generator -------------------------------------+------------------------------------- Reporter: trommler | Owner: trommler Type: feature request | Status: new Priority: normal | Milestone: 7.12.1 Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Linux Architecture: powerpc64 | Type of failure: Difficulty: Project (more | None/Unknown than a week) | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- I have started work on a native code generator for PowerPC 64 bit by extending the 32 bit code generator. The code is hosted on github: [https://github.com/trommler/ghc/tree/native] So far I plan to support the old ELF v1.9 ABI on big endian. I might look into little endian and ELF 2.0 later. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9863> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9839: RTS options parser silently accepts invalid flags
by GHC 05 Jul '15

05 Jul '15

#9839: RTS options parser silently accepts invalid flags -------------------------------------+------------------------------------- Reporter: adamgundry | Owner: simonmar Type: bug | 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: Incorrect Blocked By: | result at runtime Related Tickets: #4243 | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- RTS options that do not take arguments (such as `-T`) silently ignore anything that comes afterwards. For example, `+RTS -T,-s` or `+RTS -T-s` turns on collection of GC statistics (`-T`) but does not print out a summary (`-s`). Instead, this should produce an error message. Otherwise, users may mistakenly think that options have been applied. (This has just bitten us in a production system.) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9839> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8206: Add support for Portable Native Client
by GHC 05 Jul '15

05 Jul '15

#8206: Add support for Portable Native Client -------------------------------------------------+------------------------- Reporter: guest | Owner: Alex Type: feature request | Sayers Priority: normal | Status: new Component: Compiler | Milestone: Keywords: NaCl PNaCl Portable Native | Version: Client pexe | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Project (more than a week) | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: -------------------------------------------------+------------------------- == Motivation == [http://www.chromium.org/nativeclient/pnacl/building-and-testing-portable- native-client Portable Native Client] (PNaCl) is a feature in Google Chrome which (roughly) allows it to use LLVM bitcode like browsers use javascript today. The bitcode is downloaded, validated, compiled, and (safely) executed, with access to an API for manipulating the DOM of the page which loaded it. The dream: Haskell executed in the browser at near- native speed. Unfortunately, while GHC has an LLVM backend, the bitcode it generates doesn't satisfy the PNaCl validator. == Portable Native Client == The user visits a page with an <embed> tag pointing to a "pexe" - a PNaCl bitcode file. The bitcode is downloaded and streamed first into a code validator, and then into a compiler. The resulting machine code is then executed as a memory-protected process. The [https://developers.google.com /native-client/pepperc/ Pepper API], a library Google provides, provides access to the browser for things like connecting to websockets, playing audio, and communicating with javascript running on the page. PNaCl is present in Chrome 29 (go to chrome://flags to enable it), and will be enabled for arbitrary sources (the "open web") in Chrome 30. Mozilla have announced that they don't intend to support Native Client. == The Easily-Fixed == The pexe bitcode format is a frozen subset of LLVM bitcode. The PNaCl toolchain provides `pnacl-finalize`, which translates LLVM bitcode into pexe bitcode. PNaCl [http://www.chromium.org/nativeclient/pnacl/bitcode- abi##callingconventions only allows] the standard "ccc" calling convention, whereas GHC likes to use its own "cc 10" calling convention. You can make GHC use ccc by using an unregisterised build, for a slow-down factor of about 2. It seems likely that code-next-to-tables will upset the validator. If so, this can be turned off for a small performance hit. == The Not-So-Easily-Fixed == The validator requires that requests for IO are sent to Pepper. PNaCl also requires that you use newlib instead of glibc. Spawning new processes is forbidden (although creating pthreads is fine). It also seems likely that the validator with take umbrage at calls to `mmap`, which the GHC runtime uses to request memory allocation. It seems, therefore, that significant chunks of the RTS will have to be ported. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8206> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8353: Easy way to defer type errors
by GHC 04 Jul '15

04 Jul '15

#8353: Easy way to defer type errors ------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: GHCi | 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: | ------------------------------------+------------------------------------- A number of comments I've heard recently have focused on the joy of `-fdefer-type-errors`, especially for newcomers to Haskell. However, in GHCi, one has to 1. be aware that `-fdefer-type-errors` exists 2. know the `:set ...` syntax to turn it on, and then 3. is stuck with this setting on until they turn it off Instead, I propose new `:load!` and `:reload!` commands (abbreviated to `:l!` and `:r!`) which turn on `-fdefer-type-errors` just for that one command. When a load or reload fails, the error message could suggest these alternate forms. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8353> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9723: Give Tab warning only once per file
by GHC 04 Jul '15

04 Jul '15

#9723: Give Tab warning only once per file -------------------------------------+------------------------------------- Reporter: nomeata | Owner: Type: feature request | Status: new Priority: low | Milestone: Component: Compiler | 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: -------------------------------------+------------------------------------- Currently, when compiling a tabbed file, GHC spits out a huge number of warnings: {{{ Main.hs:1:1: Warning: Tab character [..] Main.hs:89:1: Warning: Tab character Main.hs:90:1: Warning: Tab character Main.hs:91:1: Warning: Tab character Main.hs:92:1: Warning: Tab character Main.hs:99:4: Warning: Tab character Main.hs:100:4: Warning: Tab character Main.hs:101:4: Warning: Tab character }}} This is annoying and not very nice to our users. I suggest to replace it by {{{ This file contains tabs (e.g. line n column m); please use spaces instead }}} or (to be nice to tools that parse this output) {{{ Main.hs:1:1: Tab found here, and in n further locations. Please use spaces instead. }}} (This is clearly a low priority request, but also possibly some low- hanging fruit for new contributors.) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9723> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8881: No way to unsubscribe a bug
by GHC 04 Jul '15

04 Jul '15

#8881: No way to unsubscribe a bug ------------------------------------+------------------------------------- Reporter: nomeata | Owner: hvr Type: feature request | Status: new Priority: normal | Milestone: Component: Trac & Git | Version: Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- The current trac settings are so that when I comment on a bug, I am automatically subscribed to it. This is good, but there should be way to unsubscribe from a bug as well. Also, and I’m not sure if this is the same thing or not, if I put myself in the “Observer” list (possibly wrong translation), I cannot undo that. Generally, we might give our users more permissions, e.g. to edit ticket descriptions (and not just the summary). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8881> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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