December 2016 - ghc-tickets

[GHC] #12994: Module and export level signature thinning in Backpack
by GHC 11 Jan '17

11 Jan '17

#12994: Module and export level signature thinning in Backpack -------------------------------------+------------------------------------- Reporter: ezyang | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Type checker) | Keywords: backpack | 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 problem.** We want to write signature packages to allow us to reuse signatures, but Backpack in its current incarnation forces us to depend on ALL of the signatures from the signature package. This is troublesome if we only really needed a subset of the signatures from the package. What we'd like is a way to "thin" out the signatures, keeping only the ones we need. In the original design of Backpack, this was not allowed, because if a signature was requiring a function so that a module from that package could use it, you're not permitted to just drop that requirement (someone really needs it!) But signature packages: packages that consist of only signatures (no modules) do not have any such requirement. So let's allow module and export level signature thinning here. **Design.** First, during the course of mix-in linking we infer if a package is a signature package or not. A package is a signature package if it does not have any modules, and itself depends only on fully instantiated packages or signature packages. A signature package is eligible for requirement thinning. A signature package can be thinned at the module level using the `signature-mixins` field, by saying `include-signatures: sig-pkg (A)` (we don't reuse `mixins` field to distinguish signature packages from regular indefinite packages); this means that we only are bringing the signature `A` into scope. If `A` imports another signature `B`, the user is obligated to also bring that signature into scope (if they do not, we will error, although this can only be done by GHC.) By default, all signatures in scope at a name get merged to a name. We add a pragma for controlling what declarations from packages get merged in: {{{ signature A where {-# MERGE "sig-pkg" (T, S, foo, bar, baz) #-} data T qux :: T -> T }}} This line means, "merge in the declarations T, foo, bar, baz from the signature in sig-pkg." Two things to note: 1. If `foo :: S`, you're obligated to also declare `S` in the import list, even if you are not otherwise using it. The reason for this is to make it always explicit what is going to be required in the end. 2. Even if `T` is in the merge list, you still have to declare it locally if you want to make use of it. These are not imports! (:TODO: There is no provision for disambiguating between two signatures from the same package, but mix-linked differently. This seems like a pretty rare case.) The semantics is that we proceed as we do now, but when merging, we apply the explicit import list to reduce the set of entities we actually typecheck and merge in (checking, however, to ensure that these are all well-formed.) That's it, I think. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12994> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12808: For primitive (Addr#) operations, Loop Invariant Code Flow not lifted outside the loop...
by GHC 11 Jan '17

11 Jan '17

#12808: For primitive (Addr#) operations, Loop Invariant Code Flow not lifted outside the loop... -------------------------------------+------------------------------------- Reporter: GordonBGood | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- '''Background:''' I've been intrigued investigating whether GHC can produce code "as fast as Cee (C/C++/Rust/etc.)" by-any-means-possible, and have been using the very tight inner composite culling loops (purely integer operations) of a basic Sieve of Eratosthenes implementation as a test vehicle. '''Synopsis:''' This is a follow-on of the work leading to finding the efficiency problem described in ticket #12798, but involves pushing the speed even further as per the method described for "primesieve as per [http://primesieve.org/] in the "Highly optimized inner loop" section. '''Description of test code:''' Essentially, this method involves extreme loop unrolling with very imperative code although coded functionally; in the case of the following code it means that, recognizing that for all odd primes (which they all are other than two), and that all word sizes are of an even number of bits, there will be a repeating pattern of composite number culls that repeats every word size number of bits. Thus for a word size of one eight-bit byte, we can unroll to eight composite culls in the body of one loop, with loops cases for the primes modulo 8 of 1, 3, 5, and 7, and for the eight bit start positions (b0..b7) meaning there are four times eight is 32 loop cases. When there are no longer a full eight culls left, the culling reverts to conventional single-cull-per-loop as per the test program of ticket #12798. To do this using GHC we need pointer arithmetic, and the only way to implement pointer arithmetic in GHC is to use the Addr# primitive. GHC/Haskell has one other slight overhead over Cee languages in that we need to move the culling array to a pinned array to avoid having it moved while the culling is going on and then move it back when finished but this takes a negligible amount of time (one percent or so) as compared to the culling. As usual for test programs, the culling operations are repeated in a loop for a number of times to give more accurate timing not influenced by execution not related to the culling. All of this is included in the following code (truncated as to loop coses for inclusion here): {{{#!hs -- EfficiencyBug.hs -- showing that there is a register loop invariant bug in generation of assembler code... -- LLVM shows the bug clearer since the code is generally a little faster... {-# LANGUAGE FlexibleContexts, BangPatterns, MagicHash, UnboxedTuples #-} {-# OPTIONS_GHC -O2 -rtsopts -keep-s-files #-} -- or -O2 -fllvm import Data.Word import Data.Bits import Data.Array.ST (runSTUArray) import Data.Array.Base import GHC.ST ( ST(..) ) import GHC.Exts numLOOPS = 10000 :: Int -- Uses a very simple Sieve of Eratosthenes for fixed 2 ^ 18 range (so one L1 cache size) to prove it. twos :: UArray Int Word32 twos = listArray (0, 31) [1 `shiftL` i | i <- [0 .. 31]] soep1 :: () -> [Word32] soep1() = 2 : [fromIntegral i * 2 + 3 | (i, False) <- assocs bufb] where bufb = runSTUArray $ do let bfBts = (256 * 1024) `div` 2 -- to 2^18 + 2 is 128 KBits = 16 KBytes bf <- newArray (0, bfBts - 1) False :: ST s (STUArray s Int Bool) cullb bf cullb bf@(STUArray l u n marr#) = ST $ \s0# -> case getSizeofMutableByteArray# marr# s0# of { (# s1#, n# #) -> let loop t mr# s0# = -- cull a number of times to test timing if t <= 0 then (# s0#, STUArray l u n mr# #) else case getSizeofMutableByteArray# mr# s0# of { (# s1#, n# #) -> case newPinnedByteArray# n# s1# of { (# s2#, marr'# #) -> case copyMutableByteArray# mr# 0# marr'# 0# n# s2# of { s3# -> case unsafeFreezeByteArray# marr'# s3# of { (# s4#, arr# #) -> -- must do this case byteArrayContents# arr# of { adr# -> -- to obtain the addr# here let cullp i@(I# i#) sp# = let !p@(I# p#) = i + i + 3 in let !s@(I# s#) = (p * p - 3) `div` 2 in if s >= n then case copyMutableByteArray# marr'# 0# mr# 0# n# sp# of so# -> (# so#, mr# #) else let !(UArray _ _ _ tarr#) = twos in case readWord64Array# marr# (i# `uncheckedIShiftRL#` 6#) sp# of { (# sp0#, v0# #) -> case (v0# `and#` ((int2Word# 1#) `uncheckedShiftL#` (i# `andI#` 63#))) `eqWord#` (int2Word# 0#) of 0# -> cullp (i + 1) sp0# -- not prime _ -> -- is prime -- most program execution time spent in the following tight loops. -- the following code implments extream loop unrolling... let !pi@(I# pi#) = fromIntegral p in let !sw@(I# sw#) = s `shiftR` 3 in let !sb@(I# sb#) = s .&. 7 in let p1 = sb + pi in let !(I# r1#) = p1 `shiftR` 3 in let p2 = p1 + pi in let !(I# r2#) = p2 `shiftR` 3 in let p3 = p2 + pi in let !(I# r3#) = p3 `shiftR` 3 in let p4 = p3 + pi in let !(I# r4#) = p4 `shiftR` 3 in let p5 = p4 + pi in let !(I# r5#) = p5 `shiftR` 3 in let p6 = p5 + pi in let !(I# r6#) = p6 `shiftR` 3 in let p7 = p6 + pi in let !(I# r7#) = p7 `shiftR` 3 in let !lmt@(I# lmt#) = (fromIntegral n `shiftR` 3) - p7 in let !lmt1# = plusAddr# adr# lmt# in let !strt# = plusAddr# adr# sw# in let !(I# n#) = n in let (# !so#, !sco# #) = case ((((p - 1) `div` 2) .&. 3) `shiftL` 3) + sb of { 0 -> let cull c# sp# = case c# `ltAddr#` lmt1# of 0# -> (# c#, sp# #) _ -> case readWord8OffAddr# c# 0# sp# of { (# sp0#, v0# #) -> case writeWord8OffAddr# c# 0# (v0# `or#` (int2Word# 1#)) sp0# of { sp1# -> case readWord8OffAddr# c# r1# sp1# of { (# sp2#, v1# #) -> case writeWord8OffAddr# c# r1# (v1# `or#` (int2Word# 2#)) sp2# of { sp3# -> case readWord8OffAddr# c# r2# sp3# of { (# sp4#, v2# #) -> case writeWord8OffAddr# c# r2# (v2# `or#` (int2Word# 4#)) sp4# of { sp5# -> case readWord8OffAddr# c# r3# sp5# of { (# sp6#, v3# #) -> case writeWord8OffAddr# c# r3# (v3# `or#` (int2Word# 8#)) sp6# of { sp7# -> case readWord8OffAddr# c# r4# sp7# of { (# sp8#, v4# #) -> case writeWord8OffAddr# c# r4# (v4# `or#` (int2Word# 16#)) sp8# of { sp9# -> case readWord8OffAddr# c# r5# sp9# of { (# sp10#, v5# #) -> case writeWord8OffAddr# c# r5# (v5# `or#` (int2Word# 32#)) sp10# of { sp11# -> case readWord8OffAddr# c# r6# sp11# of { (# sp12#, v6# #) -> case writeWord8OffAddr# c# r6# (v6# `or#` (int2Word# 64#)) sp12# of { sp13# -> case readWord8OffAddr# c# r7# sp13# of { (# sp14#, v7# #) -> case writeWord8OffAddr# c# r7# (v7# `or#` (int2Word# 128#)) sp14# of { sp15# -> cull (plusAddr# c# pi#) sp15# }}}}}}}}}}}}}}}} in cull strt# sp0#; 1 -> let cull c# sp# = case c# `ltAddr#` lmt1# of 0# -> (# c#, sp# #) _ -> case readWord8OffAddr# c# 0# sp# of { (# sp0#, v0# #) -> case writeWord8OffAddr# c# 0# (v0# `or#` (int2Word# 2#)) sp0# of { sp1# -> case readWord8OffAddr# c# r1# sp1# of { (# sp2#, v1# #) -> case writeWord8OffAddr# c# r1# (v1# `or#` (int2Word# 4#)) sp2# of { sp3# -> case readWord8OffAddr# c# r2# sp3# of { (# sp4#, v2# #) -> case writeWord8OffAddr# c# r2# (v2# `or#` (int2Word# 8#)) sp4# of { sp5# -> case readWord8OffAddr# c# r3# sp5# of { (# sp6#, v3# #) -> case writeWord8OffAddr# c# r3# (v3# `or#` (int2Word# 16#)) sp6# of { sp7# -> case readWord8OffAddr# c# r4# sp7# of { (# sp8#, v4# #) -> case writeWord8OffAddr# c# r4# (v4# `or#` (int2Word# 32#)) sp8# of { sp9# -> case readWord8OffAddr# c# r5# sp9# of { (# sp10#, v5# #) -> case writeWord8OffAddr# c# r5# (v5# `or#` (int2Word# 64#)) sp10# of { sp11# -> case readWord8OffAddr# c# r6# sp11# of { (# sp12#, v6# #) -> case writeWord8OffAddr# c# r6# (v6# `or#` (int2Word# 128#)) sp12# of { sp13# -> case readWord8OffAddr# c# r7# sp13# of { (# sp14#, v7# #) -> case writeWord8OffAddr# c# r7# (v7# `or#` (int2Word# 1#)) sp14# of { sp15# -> cull (plusAddr# c# pi#) sp15# }}}}}}}}}}}}}}}} in cull strt# sp0#; -- and so on for 30 more cases... _ -> (# strt#, sp0# #) {- normally never taken case, all cases covered -} } in let !ns# = ((minusAddr# so# adr#) `uncheckedIShiftL#` 3#) +# sb# in -- extreme loop unrolling ends here; remaining primes culled conventionally... let cull j# sc# = -- very tight inner loop case j# <# n# of 0# -> cullp (i + 1) sc# _ -> let i# = j# `andI#` 31# in let !sh# = indexWord32Array# tarr# i# in -- (1 `shiftL` (j .&. 31))) let w# = j# `uncheckedIShiftRL#` 5# in case readWord32Array# marr'# w# sc# of { (# sc0#, ov# #) -> case writeWord32Array# marr'# w# (ov# `or#` sh#) sc0# of { sc1# -> cull (j# +# pi#) sc1# }} in cull ns# sp0# } in case cullp 0 s4# of (# sp#, mrp# #) -> loop (t - 1) mrp# sp# }}}}} in loop numLOOPS marr# s1# } main = print $ length $ soep1() }}} '''The problem:''' The problem is in the innermost loop of the cases, for which case "0" the following assembly code (using -fllvm) is produced: {{{ seGU_info$def: # BB#0: # %cgRL cmpq %r14, 70(%rbx) jbe .LBB35_1 .align 16, 0x90 .LBB35_2: # %cgRJ # =>This Inner Loop Header: Depth=1 movq 14(%rbx), %rcx movq 22(%rbx), %rdx movq 30(%rbx), %rsi movq 38(%rbx), %rdi movq 46(%rbx), %r8 movq 54(%rbx), %r9 movq 62(%rbx), %r10 movq 6(%rbx), %rax addq %r14, %rax orb $1, (%r14) orb $2, (%rcx,%r14) orb $4, (%rdx,%r14) orb $8, (%rsi,%r14) orb $16, (%rdi,%r14) orb $32, (%r8,%r14) orb $64, (%r9,%r14) orb $-128, (%r10,%r14) cmpq 70(%rbx), %rax movq %rax, %r14 jb .LBB35_2 jmp .LBB35_3 .LBB35_1: movq %r14, %rax .LBB35_3: # %cgRK movq (%rbp), %rcx movq %rax, %rbx rex64 jmpq *%rcx # TAILCALL }}} One can readily see that the compiler is not lifting the Loop Invariant Code Flow as in initializing the registers to outside the inner loop, meaning there are many register loads from memory which are not necessary. '''Desired results:''' The desired assembly code is something like the following, which is similar to what is produced by Cee (C/C++/Rust/etc.): {{{ seGU_info$def: # BB#0: # %cgRL movq 14(%rbx), %rcx movq 22(%rbx), %rdx movq 30(%rbx), %rsi movq 38(%rbx), %rdi movq 46(%rbx), %r8 movq 54(%rbx), %r9 movq 62(%rbx), %r10 movq 6(%rbx), %rax movq 70(%rbx), %rbx cmpq %r14, %rbx jbe .LBB35_1 .align 16, 0x90 .LBB35_2: # %cgRJ # =>This Inner Loop Header: Depth=1 orb $1, (%r14) orb $2, (%rcx,%r14) orb $4, (%rdx,%r14) orb $8, (%rsi,%r14) orb $16, (%rdi,%r14) orb $32, (%r8,%r14) orb $64, (%r9,%r14) orb $-128, (%r10,%r14) addq %rax, %r14 cmpq %rbx, %rax jb .LBB35_2 jmp .LBB35_3 .LBB35_1: movq %r14, %rax .LBB35_3: # %cgRK movq (%rbp), %rcx movq %rax, %rbx # rbx clobbered here anyway rex64 jmpq *%rcx # TAILCALL }}} '''Full testing:''' The actual unrolled loop code is too long to post here, but to verify the result is correct (23000) and the performance, the full actual file is attached here. Due to the magic of modern CPU instruction fusion, the code is not as slow as it would indicate by the number of increased instructions, but while it is about twice as fast as when culled conventionally (Intel Skylake), it is about half again as slow as Cee. On an Intel Sky Lake i5-6500 (running at 3.5 GHz for single threading), this takes about one second, about two seconds culled conventionally, but only about 0.6 seconds for Rust/LLVM (with the assembly code output essentially identical to the "desired" code). '''Other back ends and targets:''' Although the code generated by the native NCG has other problems (not moving the loop test to the end of the loop to avoid one jump, and not combining the read and modify and store instructions into the single available instruction), it exhibits the same problem as to not lifting the Loop Invariant Code Flow register initialization. Although this code is x86_64, the problem also applies to x86 code even though the x86 architecture doesn't have enough registers to do this in one loop and needs to be split into two loops culling only four composites per loop, but there still is a significant gain in speed. Although not tested, it probably also applies to other targets such as ARM (which has many general purpose registers). '''Conclusion:''' The use of Addr# primitives is probably not a frequent use case, but as shown here that when one needs their use, they should be efficient. I considered that GHC may intentionally limit the performance of these unsafe primitives to limit their use unless absolutely necessary as in marshalling, something as C## does for the use of unsafe pointers, but surely GHC would not do that as the target programmers are different. '''If this and ticket #12798 were fixed, for this use case the GHC code would be within a percent or two of the performance of Cee.''' -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12808> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12990: Partially applied constructors with unpacked fields simplified badly
by GHC 10 Jan '17

10 Jan '17

#12990: Partially applied constructors with unpacked fields simplified badly -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When a constructor is partially applied to at least one unpacked field, the simplifier produces pretty lousy results. {{{#!hs data Foo a = Foo !Int a silly :: ((a -> Foo a) -> r) -> r silly f = f (Foo 3) }}} compiles to {{{ -- RHS size: {terms: 9, types: 7, coercions: 0} $WFoo :: forall a. Int -> a -> Foo a $WFoo = \ (@ a_aqI) (dt_ayl :: Int) (dt_aym :: a_aqI[sk:1]) -> case dt_ayl of { I# dt_ayn -> Foo dt_ayn dt_aym } -- RHS size: {terms: 2, types: 0, coercions: 0} silly2 :: Int silly2 = I# 3# -- RHS size: {terms: 3, types: 3, coercions: 0} silly1 :: forall a. a -> Foo a silly1 = \ (@ a_ayG) -> $WFoo silly2 -- RHS size: {terms: 5, types: 9, coercions: 0} silly :: forall a r. ((a -> Foo a) -> r) -> r silly = \ (@ a_ayG) (@ r_ayH) (f_axY :: (a -> Foo a) -> r) -> f_axY silly1 }}} That is, GHC represents `Foo 3` as a closure containing a ''boxed'' `Int`. Manually eta-expanding would fix it. {{{#!hs silly :: ((a -> Foo a) -> r) -> r silly f = f (\x -> Foo 3 x) }}} compiles to {{{#!hs -- RHS size: {terms: 5, types: 4, coercions: 0} silly1 :: forall a. a -> Foo a silly1 = \ (@ a_ayO) (x_ay9 :: a) -> Foo 3# x_ay9 -- RHS size: {terms: 5, types: 9, coercions: 0} silly :: forall a r. ((a -> Foo a) -> r) -> r silly = \ (@ a_ayO) (@ r_ayP) (f_ay8 :: (a -> Foo a) -> r) -> f_ay8 silly1 }}} in which the `Int` is unpacked into the closure. This transformation is valid whenever the value to be stored unpacked is known not to be bottom, and is certainly a good idea if it's known to have been forced. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12990> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13049: Make `-dead_strip` the default on Darwin
by GHC 10 Jan '17

10 Jan '17

#13049: Make `-dead_strip` the default on Darwin -------------------------------------+------------------------------------- Reporter: dobenour | 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: -------------------------------------+------------------------------------- We should make `-dead_strip` the default on Darwin. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13049> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11592: Self-kinded type varialbe accepted
by GHC 10 Jan '17

10 Jan '17

#11592: Self-kinded type varialbe accepted -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 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: -------------------------------------+------------------------------------- Found when chasing #11407 {{{ data T (a::a) = Blah -- Accepted data S (b :: a) a = ... -- Rejected with: variable ‘a’ used as a kind variable before being bound -- as a type variable. Perhaps reorder your variables? }}} But `T` should be rejected too, for the same reason as `S` -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11592> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12707: Add contributed performance testcase
by GHC 10 Jan '17

10 Jan '17

#12707: Add contributed performance testcase -------------------------------------+------------------------------------- Reporter: bgamari | Owner: bgamari Type: task | Status: new Priority: normal | Milestone: 8.2.1 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: -------------------------------------+------------------------------------- phadej was kind enough to offer a compile-time performance testcase. Add it to the testsuite or perhaps nofib. https://gist.github.com/phadej/554c2cc7e06b98142dc0fbadb6d3a47f -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12707> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11040: Split SRT tables on Mac OS
by GHC 10 Jan '17

10 Jan '17

#11040: Split SRT tables on Mac OS ----------------------------------------+--------------------------------- Reporter: olsner | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: MacOS X Architecture: Unknown/Multiple | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+--------------------------------- Split off from https://phabricator.haskell.org/D1242#inline-11490 Mac uses subsections via symbols to allow dead code stripping, but doesn't seem to do anything special with the SRT tables (in `HscMain.doCodeGen`), so either I'm missing something or Mac doesn't actually get much useful dead code stripping at all from the subsections feature because the SRT tables would keep everything alive. Perhaps Mac should just always do SRT splitting. Looks like you need to manually add `-optl-Wl,-dead_strip` to test this, since that's not enabled by default. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11040> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12958: Properly detect if GHCi is running in MinTTY
by GHC 10 Jan '17

10 Jan '17

#12958: Properly detect if GHCi is running in MinTTY -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: GHCi | Version: 8.0.1 Keywords: | Operating System: Windows Architecture: | Type of failure: Poor/confusing Unknown/Multiple | error message Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Since the user experience of GHCi is known to be rather poor when run in MinTTY (e.g., see #12720), GHCi emits a warning when it thinks it's being run in a terminal that uses MinTTY (such as Cygwin or MSYS2). [http://git.haskell.org/ghc.git/blob/17ac9b19438d5e8f6de33f99828e8c0e7c8c112… Here] is the code that checks for this in `ghci.c`: {{{#!c if (getenv("_")) { printf("WARNING: GHCi invoked via 'ghci.exe' in *nix-like shells (cygwin-bash, in particular)\n"); printf(" doesn't handle Ctrl-C well; use the 'ghcii.sh' shell wrapper instead\n"); fflush(stdout); } }}} This is a rather shoddy way to detect MinTTY's presence, however. It's quite easy to define an environmental variable named `_` in terminals that don't use MinTTY (e.g., ConEmu). After seeing Phab:D2809, I learned of a much more reliable way to detect for MinTTY's presence: {{{#!hs queryCygwinTerminal :: Win32.HANDLE -> IO Bool queryCygwinTerminal h = do fileType <- Win32.getFileType h if fileType /= Win32.fILE_TYPE_PIPE then pure False else do fn <- getFileNameByHandle h pure (("\\cygwin-" `isPrefixOf` fn || "\\msys-" `isPrefixOf` fn) && "-pty" `isInfixOf` fn && "-master" `isSuffixOf` fn) `catch` \ (_ :: IOError) -> pure False getFileNameByHandle :: Win32.HANDLE -> IO String getFileNameByHandle h = do let sizeOfDWORD = sizeOf (undefined :: Win32.DWORD) let sizeOfWchar = sizeOf (undefined :: CWchar) -- note: implicitly assuming that DWORD has stronger alignment than wchar_t let bufSize = sizeOfDWORD + mAX_PATH * sizeOfWchar allocaBytes bufSize $ \ buf -> do getFileInformationByHandleEx h fileNameInfo buf (fromIntegral bufSize) len :: Win32.DWORD <- peek buf let len' = fromIntegral len `div` sizeOfWchar peekCWStringLen (buf `plusPtr` sizeOfDWORD, min len' mAX_PATH) getFileInformationByHandleEx :: Win32.HANDLE -> CInt -> Ptr a -> Win32.DWORD -> IO () getFileInformationByHandleEx h cls buf bufSize = do lib <- Win32.getModuleHandle (Just "kernel32.dll") ptr <- Win32.getProcAddress lib "GetFileInformationByHandleEx" let c_GetFileInformationByHandleEx = mk_GetFileInformationByHandleEx (castPtrToFunPtr ptr) Win32.failIfFalse_ "getFileInformationByHandleEx" (c_GetFileInformationByHandleEx h cls buf bufSize) type F_GetFileInformationByHandleEx a = Win32.HANDLE -> CInt -> Ptr a -> Win32.DWORD -> IO Win32.BOOL foreign import WINAPI "dynamic" mk_GetFileInformationByHandleEx :: FunPtr (F_GetFileInformationByHandleEx a) -> F_GetFileInformationByHandleEx a }}} We should port this to C and use this in `ghci.c` instead of what we have now. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12958> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11551: Get doctests into testsuite
by GHC 10 Jan '17

10 Jan '17

#11551: Get doctests into testsuite -------------------------------------+------------------------------------- Reporter: lwm | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Core | Version: 7.10.3 Libraries | Keywords: | Operating System: Unknown/Multiple documentation, doctest | Architecture: | Type of failure: Documentation Unknown/Multiple | bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- It seems like a bit of a shame not to have Mr.Orlitzky's lovely doctests not running with the testsuite. Or perhaps to at least have some sort of `make doctest`. If there is some interest to get this working, I'd like to take a look at submitting a patch. Here are the previous documentation patches I can find: https://phabricator.haskell.org/p/mjo/ I can see the following files that have doctests: {{{ ruby-2.2.1 ~/work/contributing/ghc (master) [12:35:44] lwm$ grep -R "=== __Examples__" libraries/base/ | uniq grep: libraries/base/Data/Maybe.hs:-- ==== __Examples__ libraries/base/Data/Either.hs:-- ==== __Examples__ libraries/base/Data/List.hs:-- ==== __Examples__ libraries/base/Data/Functor.hs:-- ==== __Examples__ libraries/base/Data/Bool.hs:-- ==== __Examples__ libraries/base/Data/Char.hs:-- ==== __Examples__ libraries/base/GHC/Unicode.hs:-- ==== __Examples__ libraries/base/Text/Printf.hs:-- ==== __Examples__ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11551> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8761: Make pattern synonyms work with Template Haskell
by GHC 10 Jan '17

10 Jan '17

#8761: Make pattern synonyms work with Template Haskell ------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Template Haskell | Version: 7.8.1-rc1 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- Template Haskell has no support for pattern synonyms. This should be added. Specifically: * Create syntax in `Language.Haskell.TH.Syntax` and corresponding functions in `Language.Haskell.TH.Lib` * Support in !DsMeta for desugaring pattern synonym quotations. See `rep_bind`. * Support in Convert for splicing in pattern synonyms. * Support in !TcSplice for reifying pattern synonyms. See `reifyThing`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8761> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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