[GHC] #12757: Compiled program segfaults at -O1
#12757: Compiled program segfaults at -O1 -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.2 Component: Compiler | Version: 8.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime crash Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This affects GHC 8.0.2dev (d84a824cebe94711528727bcb587bfc369ec36a2) as well as GHC HEAD (c23dc6164d54eacc654516b885104dc8b7678f16) The following program results in a segfault when compiled at -O1 or more: {{{#!hs {-# LANGUAGE OverloadedStrings #-} module Main (main) where import Data.ByteString (ByteString) import qualified Data.ByteString as B answers :: [ByteString] answers = map (B.filter (/= 0x20)) [ "e3b0c442 98fc1c14 9afbf4c8 996fb924 27ae41e4 649b934c a495991b 7852b855" , "d7a8fbb3 07d78094 69ca9abc b0082e4f 8d5651e4 6d3cdb76 2d02d0bf 37c9e592" , "e4c4d8f3 bf76b692 de791a17 3e053211 50f7a345 b46484fe 427f6acc 7ecc81be" , "ba7816bf 8f01cfea 414140de 5dae2223 b00361a3 96177a9c b410ff61 f20015ad" , "248d6a61 d20638b8 e5c02693 0c3e6039 a33ce459 64ff2167 f6ecedd4 19db06c1" , "cf5b16a7 78af8380 036ce59e 7b049237 0b249b11 e8f07a51 afac4503 7afee9d1" , "cdc76e5c 9914fb92 81a1c7e2 84d73e67 f1809a48 a497200e 046d39cc c7112cd0" ] x, y :: ByteString x = "e3b0c442 98fc1c14 9afbf4c8 996fb924 27ae41e4 649b934c a495991b 7852b855" y = B.filter (/= 0x20) x main :: IO () main = do print (seq x ()) print (seq y ()) print (length answers) print (seq (head answers) ()) -- segfault! }}} {{{ $ ghc-8.0.2 -fforce-recomp --make -O1 bug.hs && ./bug [1 of 1] Compiling Main ( bug.hs, bug.o ) Linking bug ... () () 7 Segmentation fault }}} {{{ $ ghc-8.0.2 -fforce-recomp --make -O0 bug.hs && ./bug [1 of 1] Compiling Main ( bug.hs, bug.o ) Linking bug ... () () 7 () }}} I haven't yet investigated why this happens. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12757 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12757: Compiled program segfaults at -O1 -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.2 Component: Compiler | Version: 8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by hvr): I was informed by slyfox that this is much related (almost to the point of being a duplicate) of #12585, which in turn is a duplicate of #11312 I do consider this a blocker for GHC 8.0.2 as the repro-case above is code that's surely not exotic... -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12757#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12757: Compiled program segfaults at -O1 -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.2 Component: Compiler | Version: 8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Wait... how could inlining or not make a seg-fault? The above discussion shows that it can affect a boolean value, but not seg-fault! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12757#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12757: Compiled program segfaults at -O1 -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.2 Component: Compiler | Version: 8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): I've done a bisection of this on `ghc-8.0`; according to the bisection the culprit is 2a9767ed596679ddf21b7edfa9fc6410443c2a01. I have yet to verify that reverting on `ghc-8.0` `HEAD` fixes the issue. I'm currently waiting for a build to confirm this. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12757#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12757: Compiled program segfaults at -O1 -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.2 Component: Compiler | Version: 8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * cc: ezyang (added) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12757#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12757: Compiled program segfaults at -O1 -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.2 Component: Compiler | Version: 8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: #11312, #12585 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * related: => #11312, #12585 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12757#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12757: Compiled program segfaults at -O1 -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.2 Component: Compiler | Version: 8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: #11312, #12585 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): Siarheit had some insight on this. The problem here is essentially that `bytestring` traverses a `ByteString` by walking until `currPtr == ( "literal"# +# length "literal"# )` where `currPtr` is initialized with `"literal"#`. This means that if `"literal"#` is inlined twice, you will end up with `currPtr` and `"literal"# +# length "literal"#` pointing into two separate chunks of memory, with who-knows-what in between. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12757#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12757: Compiled program segfaults at -O1 -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.2 Component: Compiler | Version: 8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: #11312, #12585 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Ah! Good insight. comment:3 of #11312 would nail this problem, and we should do that anyway. Short term, not duplicating literal strings seems like the way forward. They are duplicated in `CorePrep`, apparently because of * Edwards's patch for #12076 made `CorePrep` a bit more gung ho about inlining * When inlining in `CorePrep` we use `cpe_ExprIsTrivial`, which treats all literals (including strings) as trivial and hence inlinable. No one quite knows why: see #11158 So the best path forward seems to be to fix #11158, which we want to do anyway. Then we won't duplicate string literals, and `bytestring` will probably be happy again. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12757#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12757: Compiled program segfaults at -O1
-------------------------------------+-------------------------------------
Reporter: hvr | Owner:
Type: bug | Status: new
Priority: highest | Milestone: 8.0.2
Component: Compiler | Version: 8.1
Resolution: | Keywords:
Operating System: Unknown/Multiple | Architecture:
| Unknown/Multiple
Type of failure: Runtime crash | Test Case:
Blocked By: | Blocking:
Related Tickets: #11312, #12585 | Differential Rev(s):
Wiki Page: |
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Comment (by Ben Gamari
#12757: Compiled program segfaults at -O1 -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: closed Priority: highest | Milestone: 8.0.2 Component: Compiler | Version: 8.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: #11312, #12585 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * status: new => closed * resolution: => fixed Comment: #11158 has been resolved. The fix was merged to `ghc-8.0` as 967dd5c9f59e532fe9d6484888a2bae7d02fba11. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12757#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#12757: Compiled program segfaults at -O1 -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: closed Priority: highest | Milestone: 8.0.2 Component: Compiler | Version: 8.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: #11312, #12585, | Differential Rev(s): #12855 | Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * related: #11312, #12585 => #11312, #12585, #12855 Comment: Sadly I made a silly mistake in the 8.0.2-rc1 source release; it turns out that the commit fixing #11158 didn't quite make it into the release. Consequently slyfox reported another similar issue, #12855, which is also fixed by merging the #11158 fix. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12757#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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