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[GHC] #7638: bindist refers to libgmp.so.3 which is missing on Fedora 17
by GHC 20 Apr '13

20 Apr '13

#7638: bindist refers to libgmp.so.3 which is missing on Fedora 17 ----------------------------+----------------------------------------------- Reporter: j.waldmann | Owner: Type: feature request | Status: new Priority: normal | Component: Compiler Version: 7.6.1 | Keywords: Os: Linux | Architecture: x86_64 (amd64) Failure: None/Unknown | Blockedby: Blocking: | Related: ----------------------------+----------------------------------------------- binary distribution ghc-7.6.2-x86_64-unknown-linux.tar.bz2 contains executable(s) that expect libgmp.so.3 but recent systems (Fedora 17) have libgmp.so.10 instead, and I don't see how I could roll back. No big deal, but each fix requires a recompile (of gmp, of ghc). -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7638> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6063: GHC's build-time ld-flag checks are problematic
by GHC 19 Apr '13

19 Apr '13

#6063: GHC's build-time ld-flag checks are problematic ---------------------------------+------------------------------------------ Reporter: parcs | Owner: thoughtpolice Type: bug | Status: new Priority: high | Milestone: 7.8.1 Component: Compiler | Version: 7.4.1 Keywords: | Os: Linux Architecture: Unknown/Multiple | Failure: GHC doesn't work at all Difficulty: Unknown | Testcase: Blockedby: | Blocking: Related: #4862 | ---------------------------------+------------------------------------------ Changes (by nh2): * cc: mail@… (added) Comment: Was this not fixed in #4862 9 months ago? Doesn't seem to be in 7.6.2 though ... -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6063#comment:9> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #3333: GHCi doesn't load weak symbols
by GHC 19 Apr '13

19 Apr '13

#3333: GHCi doesn't load weak symbols --------------------------------------+------------------------------------- Reporter: heatsink | Owner: akio Type: bug | Status: patch Priority: normal | Milestone: 7.6.2 Component: GHCi | Version: 6.10.4 Keywords: weak, dynamic loading | Os: Linux Architecture: x86 | Failure: None/Unknown Difficulty: Unknown | Testcase: Blockedby: 3658 | Blocking: Related: | --------------------------------------+------------------------------------- Changes (by nh2): * cc: mail@… (added) -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3333#comment:28> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7845: RebindableSyntax should allow rebinding tuples and lists
by GHC 19 Apr '13

19 Apr '13

#7845: RebindableSyntax should allow rebinding tuples and lists -----------------------------+---------------------------------------------- Reporter: exbb2 | Owner: Type: feature request | Status: new Priority: normal | Component: Compiler Version: 7.7 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- e.g. {{{ {-# LANGUAGE RebindableSyntax #-} module StrictPrelude where data [] a = [] | !a : [a] data () = () data (,) a b = (,) !a !b }}} -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7845> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5361: regSpill: out of spill slots!
by GHC 18 Apr '13

18 Apr '13

#5361: regSpill: out of spill slots! -----------------------------------------------------+---------------------- Reporter: markwright | Owner: igloo Type: bug | Status: closed Priority: highest | Milestone: 7.2.1 Component: Compiler | Version: 7.1 Resolution: fixed | Keywords: regSpill panic impossible Os: Linux | Architecture: x86_64 (amd64) Failure: Compile-time crash | Difficulty: Testcase: http://hackage.haskell.org/package/SHA | Blockedby: Blocking: | Related: -----------------------------------------------------+---------------------- Changes (by Targen): * cc: targen@… (added) Comment: This just bit me in 7.7 trying to compile SHA-1.6.1 — same spot, I believe: {{{ $ ghc Data/Digest/Pure/SHA.hs -O -fregs-graph [1 of 1] Compiling Data.Digest.Pure.SHA ( Data/Digest/Pure/SHA.hs, Data/Digest/Pure/SHA.o ) ghc: panic! (the 'impossible' happened) (GHC version 7.7 for i386-unknown-linux): regSpill: out of spill slots! regs to spill = 1743 slots left = 677 }}} The GHC invocation issued by cabal-install was quite longer, of course — that’s as minimal as I managed to get it. There is no error if I remove either -O or -fregs-graph. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5361#comment:4> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7793: GHC User’s Guide, Version 7.6.2: Page numbering errors
by GHC 17 Apr '13

17 Apr '13

#7793: GHC User’s Guide, Version 7.6.2: Page numbering errors -----------------------------+---------------------------------------------- Reporter: thorkilnaur | Owner: Type: bug | Status: new Priority: normal | Component: Documentation Version: 7.6.2 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- In The Glorious Glasgow Haskell Compilation System User’s Guide, Version 7.6.2, I find the "Introduction to GHC" on a page denoted "1/37". Chapter 10 starts on page "257/37" and "10.1 Introduction" then proceeds on page "1/37". Something seems wrong with the page numbering. Best regards Thorkil -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7793> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7815: STM fails to validate read.
by GHC 17 Apr '13

17 Apr '13

#7815: STM fails to validate read. ----------------------------------------+----------------------------------- Reporter: fryguybob | Owner: Type: bug | Status: new Priority: normal | Component: Runtime System Version: 7.7 | Keywords: STM Os: Unknown/Multiple | Architecture: x86 Failure: Incorrect result at runtime | Blockedby: Blocking: | Related: ----------------------------------------+----------------------------------- This issue was brought up by napping in {{{#haskell}}} with this paste: [http://hpaste.org/85134] (the first paste in particular) The code is: {{{ import Control.Concurrent.STM import Control.Concurrent import Control.Monad main = do dog <- newTVarIO False cat <- newTVarIO False let unset = do d <- readTVar dog c <- readTVar cat if (d || c) then retry else return () setDog = unset >> writeTVar dog True setCat = unset >> writeTVar cat True oops = do d <- readTVar dog c <- readTVar cat guard (d && c) reset = do writeTVar dog False writeTVar cat False reset' = do d <- readTVar dog c <- readTVar cat guard (d || c) reset forkIO (atomically oops >> putStrLn "Oh Noes!") forever (do forkIO (atomically setDog) forkIO (atomically setCat) atomically reset' atomically reset') }}} When run it produces: {{{ $ ghc --make test.hs -threaded -rtsopts $ ./test +RTS -N2 Oh Noes! test: thread blocked indefinitely in an STM transaction }}} The second message is just a consequence of entering an unexpected state. The first message indicates that both the transactions {{{cat}}} and {{{dog}}} committed at the same time. It does this for HEAD and 7.6. I've sketched out an interleaving that leads to this. TRec entries are in the first and third column and TVar's are in the second column. Each entry has a TVar name and the expected value followed by the new value and then a number of updates if it has been read. TVars list their value and their number of updates. {{{ A TRec TVar B TRec -- Transactions start cat F F cat F 0 cat F F -- Initial reads. dog F F dog F 0 dog F F cat F T dog F T -- Local writes in TRec's -- Validation: cat F F 0 -- B reads num_updates from cat (with ^ -- consistency check with value) cat F T cat A 0 | -- A acquires lock for cat (atomic cas) dog F F 0 ^ | -- A reads num_updates from dog (with ^ | | -- consistency check with value) | dog B 0 dog F T | -- B acquires lock for dog (atomic cas) | | ^ | | | | | Success 0 | 0 | -- read check for A Success 0 0 -- read check for B cat A 1 -- Increment version cat T 1 -- Unlock with new value dog B 1 -- Increment version dog B T -- Unlock with new value }}} What is clear here is that the version number is not enough to check in {{{check_read_only}}} because there is a gap between locking and incrementing the version. We need to know atomically that the TVar is not locked and it's version number is the same. I need to read through the right parts of Keir Fraser's thesis carefully, but it seems like the read phase here is only helpful in preventing a commit that writes back the exact value we have already seen while we are in the middle of committing. The code for {{{check_read_only}}} is here: {{{ #!c static StgBool check_read_only(StgTRecHeader *trec STG_UNUSED) { StgBool result = TRUE; ASSERT (config_use_read_phase); IF_STM_FG_LOCKS({ FOR_EACH_ENTRY(trec, e, { StgTVar *s; s = e -> tvar; if (entry_is_read_only(e)) { TRACE("%p : check_read_only for TVar %p, saw %ld", trec, s, e -> num_updates); if (s -> num_updates != e -> num_updates) { // ||s -> current_value != e -> expected_value) { TRACE("%p : mismatch", trec); result = FALSE; BREAK_FOR_EACH; } } }); }); return result; } }}} If I restore the commented out line (which appears commented out in the first commit of this code that I can find) I can't reproduce the issue, but I think there is still a problem due to the ordering of those checks: we could observe the version as the same, while it is locked, have the TVar unlock, then observe the value the same. Switching the order we can only observe the TVar unlocked if the update has been incremented (as long as we are on an architecture that ensures this such as x86). Does this seem right? One issue is that given the interleaving that above with this added check ''both'' transactions could fail to commit. I think the algorithms from Fraser avoid this, but I think it always involves invalidating another transaction (i.e. killing off any other transactions observed to be in the read check phase with an overlapping TVar in a way that results in only one winner (see page 21 section 4.4 in ''Concurrent Programming Without Locks'')). As a side note, the issue can be avoided by ensuring that the reads become writes and avoiding the read only check. But you can only become a write if the values do not have matching pointers, switching to Ints instead of Bools gets you there. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7815> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #7748: Runtime <<loop>> due to incorrect inferred type
by GHC 17 Apr '13

17 Apr '13

#7748: Runtime <<loop>> due to incorrect inferred type ----------------------------------------+----------------------------------- Reporter: jbransen | Owner: Type: bug | Status: new Priority: normal | Component: Compiler (Type checker) Version: 7.6.2 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: GHC accepts invalid program | Blockedby: Blocking: | Related: ----------------------------------------+----------------------------------- There is a bug in the type checker of 7.6.1 and 7.6.2, which accepts an incorrect type resulting in <<loop>> at runtime. Furthermore, 7.6.2 even automatically infers this incorrect type. Hence, the attached code has the following behavior: - No explicit type: Code works in 7.6.1, loops in 7.6.2 - Correct explicit type: Code works fine in 7.6.1 and 7.6.2 - Incorrect explicit type: Code loops in 7.6.1 and 7.6.2 The incorrect type has a parameter that is too polymorphic, i.e. an "a" type is accepted while the function does a pattern match on the parameter from which it is clear that it should be a Maybe type. In 7.4.* versions this incorrect type is not accepted. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7748> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6135: Unboxed Booleans
by GHC 16 Apr '13

16 Apr '13

#6135: Unboxed Booleans ---------------------------------+------------------------------------------ Reporter: benl | Owner: jstolarek Type: feature request | Status: patch Priority: normal | Milestone: 7.8.1 Component: Compiler | Version: 7.4.1 Keywords: | Os: Unknown/Multiple Architecture: Unknown/Multiple | Failure: None/Unknown Difficulty: Unknown | Testcase: Blockedby: | Blocking: Related: #605 | ---------------------------------+------------------------------------------ Comment(by simonpj): Also, use the stage-1 compiler to generate code for some tiny program like {{{ f x = if x>0 then True else False g x = x<0 }}} and check that the comparison is going to work right. -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6135#comment:49> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7436: Derived Foldable and Traversable instances become extremely inefficient due to eta-expansion
by GHC 16 Apr '13

16 Apr '13

#7436: Derived Foldable and Traversable instances become extremely inefficient due to eta-expansion --------------------------------------+------------------------------------- Reporter: shachaf | Owner: Type: bug | Status: merge Priority: normal | Milestone: 7.6.3 Component: Compiler | Version: 7.6.1 Resolution: fixed | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Runtime performance bug | Difficulty: Unknown Testcase: perf/should_runt/T7436 | Blockedby: Blocking: | Related: --------------------------------------+------------------------------------- Comment(by simonpj): This one is fixed, just awaiting merging into 7.6.3 -- Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7436#comment:22> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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