December 2017 - ghc-tickets

[GHC] #9269: Type families returning quantified types
by GHC 14 Feb '18

14 Feb '18

#9269: Type families returning quantified types ------------------------------------+------------------------------------- Reporter: pumpkin | Owner: Type: feature request | 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: | ------------------------------------+------------------------------------- Is there a fundamental reason for not being able to use quantification in a type family? I'd very much like to be able to do it, obviously turning on RankNTypes if necessary. I'm looking for things like this: {{{#!haskell type family Foo (x :: Bool) where Foo True = forall a. [a] Foo False = () }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9269> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12422: Add decidable equality class
by GHC 14 Feb '18

14 Feb '18

#12422: Add decidable equality class -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Core | Version: 8.0.1 Libraries | 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: -------------------------------------+------------------------------------- Currently, we have a `TestEquality` class {{{#!hs class TestEquality f where testEquality :: f a -> f b -> Maybe (a :~: b) }}} It would be nice to add a class for fully decidable equality. There are a few options, but this one gets to the point rather quickly: {{{#!hs data EqDec a b where NotEqual :: (forall c . a :~: b -> c) -> EqDec a b Equal :: EqDec a a class DecEq f where decEq :: f a -> f b -> EqDec a b }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12422> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14619: Output value of program changes upon compiling with -O optimizations
by GHC 12 Feb '18

12 Feb '18

#14619: Output value of program changes upon compiling with -O optimizations -------------------------------------+------------------------------------- Reporter: sheaf | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Keywords: | Operating System: Windows Architecture: x86_64 | Type of failure: Incorrect result (amd64) | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The optimisation pass seems to affect the behaviour of the attached program (a basic ray-sphere intersection test, 40 lines long, no dependencies). Specifically, compiling the attached source file with -O or -O2, and considering the definition of main: {{{#!hs result = sphereIntersection testRay testSphere main :: IO() main = do print $ result print $ sphereIntersection testRay testSphere }}} I get the troubling output: {{{ > bug.exe Just ((0.0,0.0,0.0),0.0) Just ((0.0,0.0,100.0),1.0) }}} This is especially troubling because the second component of the output should always be 1.0: {{{#!hs testRay = ((0, 0, 0),(0, 0, 1)) sphereIntersection (orig, dir@(_, _, dirz)) (c,r) | disc < 0 = Nothing | t1 > 0 = Just (t1 *> dir <+> orig, dirz) | t2 > 0 = Just (t2 *> dir <+> orig, dirz) | otherwise = Nothing where ... }}} as we are returning the "dirz" component of the input ray straight back out. On the other hand, when the program is run without optimisations, I get the expected output: {{{ > bug.exe Just ((0.0,0.0,100.0),1.0) Just ((0.0,0.0,100.0),1.0) }}} This behaviour was present on all versions of GHC that I tested (7.10.1, 8.0.1, 8.2.1, 8.2.2). I initially ran into this issue when I noticed that the profiling builds of my program produced different results, which was boiled down to this problem. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14619> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14535: ghc: panic! (the 'impossible' happened) (GHC version 8.2.1 for x86_64-apple-darwin): stack depth overflow
by GHC 12 Feb '18

12 Feb '18

#14535: ghc: panic! (the 'impossible' happened) (GHC version 8.2.1 for x86_64 -apple-darwin): stack depth overflow -------------------------------------+------------------------------------- Reporter: iTotallyExist | Owner: (none) Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 8.2.1 Keywords: panic! stack | Operating System: MacOS X depth overflow | Architecture: | Type of failure: GHCi crash Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I created a neural network library within haskell. I was able to create, test, and train the net (using data from the mNist dataset). I could only test manually (try one input at a time and compare the two outputs), so i made a function which allowed me to test many test inputs on the net at once. Recreating bug: first, load main.hs in ghci (duh) then, run the entirety of trainedNetwork.txt as a command to initialise the network (i.e. copy paste the file into the ghci command line) then run the entirety of test.txt as a command. Here you will get the error. To test with different input values for the function "test" (the function whose being run caused the crash), you can open the jupyter notebook and run the function mnistTest with higher or lower values (higher using more test cases, lower using less) and run the output of that function as a command in haskell. (i know from testing that 30 inputs does not cause a crash, but 50 does). What i know is not the problem/probably causes: I know that y was initiliased correctly. The function being run here is : {{{#!hs --takes in a network and an array of test inputs and their corresponding outputs and returns the accuracy of the network --only works for classification networks testClassification :: [Layer] -> [[Double]] -> [[Double]] -> Double testClassification net inputs outputs = testClassificationHelper net inputs outputs 0 0 testClassificationHelper :: [Layer] -> [[Double]] -> [[Double]] -> Double -> Double -> Double testClassificationHelper _ [] _ correct incorrect = (correct/(correct+incorrect)) testClassificationHelper net (input:inputs) (output:outputs) correct incorrect | netMax == outMax = next (correct+1) incorrect | otherwise = next correct (incorrect+1) where next = testClassificationHelper net inputs outputs netMax = greatestIndex (getOutput net input) outMax = greatestIndex output }}} I know that getOutput and greatestIndex work\\ I know that it works with a small amount of inputs (test3.txt is essentially the same command except instead of using the first 100 test examples of the mnist data set, it uses the first 3)\\ I know that it works when using the first 30 data points, but not with the first 50.\\ I know that doing it for the first 30 inputs only takes 2 seconds and 270 MB, while training the network took 40 minutes and 820GB, take from that what you will\\ -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14535> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12262: Binary output is not deterministic
by GHC 07 Feb '18

07 Feb '18

#12262: Binary output is not deterministic -------------------------------------+------------------------------------- Reporter: niteria | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- The goal of DeterministicBuilds (#4012) was to get ABI-compatible binaries given the same sources, flags and the environment. There's a stronger goal of getting bit-for-bit identical binaries and this ticket will track that. Known causes of binary nondeterminism: * Unique comparison * Uniques converted to strings for symbol names * everything else from #4012 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12262> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12685: getNumProcessors semantics dont match documentation
by GHC 07 Feb '18

07 Feb '18

#12685: getNumProcessors semantics dont match documentation ----------------------------------------+--------------------------------- Reporter: Llgn | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries/base | Version: 8.0.1 Keywords: | Operating System: Linux Architecture: Unknown/Multiple | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+--------------------------------- Hi, The documentation of getNumProcessors says : "Returns the number of CPUs that the machine has", but it is true only for program compiled with -threaded option. https://hackage.haskell.org/package/base-4.9.0.0/docs/GHC-Conc- Sync.html#v:getNumProcessors I guess the documentation is just misleading. Or is it a bug ? Regards -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12685> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14396: Hs-boot woes during family instance consistency checks
by GHC 05 Feb '18

05 Feb '18

#14396: Hs-boot woes during family instance consistency checks -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 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: -------------------------------------+------------------------------------- Consider this set of modules (related to #13981 but not the same) {{{ {-# LANGUAGE TypeFamilies #-} module Fam where type family XListPat a {-# LANGUAGE TypeFamilies #-} module T1 where import Fam import {-# SOURCE #-} T( SyntaxExpr ) type instance XListPat Int = SyntaxExpr {-# LANGUAGE TypeFamilies #-} module T2 where import Fam type instance XListPat Bool = Int -- T.hs-boot module T where data SyntaxExpr = S -- T.hs module T where import T1 import T2 data SyntaxExpr = S }}} Compiled with GHC 8.0, 8.2, and HEAD we get {{{ ghc.exe: panic! (the 'impossible' happened) (GHC version 8.0.2 for x86_64-unknown-mingw32): tcIfaceGlobal (local): not found You are in a maze of twisty little passages, all alike. While forcing the thunk for TyThing SyntaxExpr which was lazily initialized by initIfaceTcRn, I tried to tie the knot, but I couldn't find SyntaxExpr in the current type environment. If you are developing GHC, please read Note [Tying the knot] and Note [Type-checking inside the knot]. Consider rebuilding GHC with profiling for a better stack trace. Contents of current type environment: [] }}} Reason: * After renaming, but before type checking, we try to do family-instance consistency checking in `FamInst.checkFamInstConsistency` * To do so we have to pull in the axioms from `T1` and `T2`. * Then we poke on those axioms, to check consistency, we pull in both LHS and RHS of the type instances. * Alas that pulls on `SyntaxExpr`, which we have not yet typechecked. I don't think it's enough to make lazier the loading of the RHS of the axiom, because I think `checkFamInstConsistency` ends up looking at the RHS too. See the call to `compatibleBranches` in `lookupFamInstEnvConflicts`. This setup is actually used in Alan's `wip/ttg-2017-10-13` branch for Trees That Grow. Here module `T` is `HsExpr`, `T1` is `HsPat`. And indeed GHC 8.0 crashes when compiling this branch. SO it's becoming a real problem. Generally I'm concerned that #13981 may also become more pressing; and #14080 is still open -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14396> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8684: hWaitForInput cannot be interrupted by async exceptions on unix
by GHC 05 Feb '18

05 Feb '18

#8684: hWaitForInput cannot be interrupted by async exceptions on unix ------------------------------------+------------------------------------- Reporter: nh2 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries/base | 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: | ------------------------------------+------------------------------------- http://hackage.haskell.org/package/base-4.6.0.1/docs/System-Timeout.html claims that {{{timeout}}} can interrupt {{{hWaitForInput}}}, but in fact that's false (e.g. mentioned in https://ghc.haskell.org/trac/ghc/ticket/7353#comment:4) {{{ -- import Control.Concurrent import System.IO import System.Timeout main = timeout (1 * 1000000) $ hWaitForInput stdin (5 * 1000) }}} will not be killed after 1 second, but instead wait for the full 5 seconds timeout passed to {{{hWaitForInput}}}. The implementation is {{{ready}}} at http://www.haskell.org/ghc/docs/latest/html/libraries/base/src/GHC-IO- FD.html, where we have two foreign calls: {{{safe fdReady}}} and {{{unsafe unsafe_fdReady}}}. The actual C implementation is at https://github.com/haskell- suite/base/blob/master/cbits/inputReady.c#L16. It uses {{{select}}} on Unix, and does check for {{{EINTR}}}, so I believe that according to http://www.haskell.org/ghc/docs/7.6.3/html/users_guide/ffi.html#ffi- interruptible both foreign calls can be replaced by a single {{{interruptible}}} one. Is that true? If not, it's a documentation bug in {{{timeout}}} at least. Also, does {{{interruptible}}}, apart from allowing the function to be interrupted, behave more like {{{safe}}} or {{{unsafe}}}? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8684> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8228: GHC built under Windows does not generate dyn_hi files
by GHC 04 Feb '18

04 Feb '18

#8228: GHC built under Windows does not generate dyn_hi files ------------------------------+-------------------------------------------- Reporter: ezyang | Owner: Type: bug | Status: new Priority: high | Milestone: 7.8.1 Component: Compiler | Version: 7.7 Keywords: | Operating System: Windows Architecture: | Type of failure: GHC doesn't work at all Unknown/Multiple | Test Case: cabal01 Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | ------------------------------+-------------------------------------------- I found cabal01 failing with: {{{ =====> cabal01(normal) 1 of 1 [0, 0, 0] cd . && $MAKE -s --no-print-directory cabal01 VANILLA=--enable-library- vanilla PROF=--disable-l ibrary-profiling DYN=--enable-shared </dev/null >cabal01.run.stdout 2>cabal01.run.stderr Wrong exit code (expected 0 , actual 2 ) Stdout: Stderr: Creating library file: dist\build\libHStest-1.0-ghc7.7.20130904.dll.a setup.exe: Error: Could not find module: A with any suffix: ["dyn_hi"] in the search path: ["dist\\build"] make[2]: *** [cabal01] Error 1 }}} but I bet some of the other failures are due to this. Indeed, in dist/build, there are no dyn_hi files When I look more closely at the commands being run, I see: {{{ bash.exe-3.1$ c:/Users/ezyang/Dev/ghc-validate/inplace/bin/ghc-stage2.exe --make -fbuilding-ca bal-package -O -static -dynamic-too -dynosuf dyn_o -dynhisuf dyn_hi -outputdir dist/build -odi r dist/build -hidir dist/build -stubdir dist/build -i -idist/build -i. -idist/build/autogen -I dist/build/autogen -Idist/build -optP-include -optPdist/build/autogen/cabal_macros.h -package- name test-1.0 -hide-all- packages -no-user-package-db -package-db local.db -package-db dist/pac kage.conf.inplace -package-id base-4.7.0.0-inplace -XHaskell98 -XForeignFunctionInterface A B. A -fforce-recomp -dcore-lint -dcmm-lint -dno-debug-output -no-user-package-db [1 of 2] Compiling B.A ( B\A.hs, dist\build\B\A.o ) [2 of 2] Compiling A ( A.hs, dist\build\A.o ) }}} which should result in dyn_hi files but does not. I haven't traced it any further yet. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8228> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14244: ghc-prim: hs_atomicread* and hs_atomicwrite* missing barriers
by GHC 04 Feb '18

04 Feb '18

#14244: ghc-prim: hs_atomicread* and hs_atomicwrite* missing barriers -------------------------------------+------------------------------------- Reporter: trommler | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Prelude | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect result Unknown/Multiple | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: #12537 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The comments in `compiler/prelude/primops.txt.pp` for both operations say "... Implies a full memory barrier." The implementation does not issue any barriers as exemplified by the 32-bit variants as can be seen in the excerpts from `libraries/ghc- prim/cbits/atomic.c`. {{{#!c StgWord hs_atomicread32(StgWord x) { return *(volatile StgWord32 *) x; } }}} and {{{#!c void hs_atomicwrite32(StgWord x, StgWord val) { *(volatile StgWord32 *) x = (StgWord32) val; } }}} The native code generator for X86/amd64 and the LLVM backend do not generate calls to these functions but generate the necessary barrier (`mfence`) directly and thus are not affected by this issue. There are no gcc `__sync_*` intrinsics for the two operations. The new `__atomic_*` intrinisics have the required operations but require gcc 4.7 or later. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14244> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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