[GHC] #9480: Segfault in GHC API code using Shelly
#9480: Segfault in GHC API code using Shelly -------------------------------------+------------------------------------- Reporter: agibiansky | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHC API | Version: 7.8.3 Keywords: | Operating System: Linux Architecture: Unknown/Multiple | Type of failure: Runtime Difficulty: Unknown | crash Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- A segfault occurs when using the GHC API with Shelly. I do not know why. Here is a code snippet that triggers it: {{{#!hs import GHC import GHC.Paths ( libdir ) import DynFlags main = runGhc (Just libdir) $ do dflags <- getSessionDynFlags setSessionDynFlags $ dflags { hscTarget = HscInterpreted, ghcLink = LinkInMemory } imports <- mapM parseImportDecl ["import Shelly", "import Prelude"] setContext $ map IIDecl imports runStmt "shelly undefined" RunToCompletion }}} Note that on Mac OS X, this has no output whatsoever. The segfault occurs on Ubuntu 14.04, with `uname -a` outputting the following: {{{ Linux yed 3.13.0-34-generic #60-Ubuntu SMP Wed Aug 13 15:45:27 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux }}} I cannot find any way to get this to work and have no idea what's up with this or why shelly triggers it. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9480 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9480: Segfault in GHC API code using Shelly -------------------------------------+------------------------------------- Reporter: agibiansky | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHC API | Version: 7.8.3 Resolution: | Keywords: Operating System: Linux | Architecture: Unknown/Multiple Type of failure: Runtime | Difficulty: Unknown crash | Blocked By: Test Case: | Related Tickets: #8935 Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Changes (by rwbarton): * related: => #8935 Comment: More `environ` nightmares, with the added twist of the GHCi linker. The problem arises here in `PrelIOUtils.o`: {{{ 00000000000002b0 <__hscore_environ>: 2b0: 48 8b 05 00 00 00 00 mov 0x0(%rip),%rax # 2b7 <__hscore_environ+0x7> 2b3: R_X86_64_PC32 environ-0x4 2b7: c3 retq }}} `-Dl` has the following to say about this: [edited slightly for readability] {{{ Rel entry 2 is raw( 0x2b3 0x3a00000002 0xfffffffffffffffc) lookupSymbol: looking up environ initLinker: start initLinker: idempotent return lookupSymbol: symbol not found `environ' resolves to 0x7ffff7039fd8 Reloc: P = 0x44f0e2f3 S = 0x7ffff7039fd8 A = 0xfffffffffffffffc }}} Now `environ` is too far away to use a PC-relative 32-bit reference, so the GHCi linker makes a jump island, but that's nonsense since `environ` isn't a function but rather a pointer to an array of C strings. But, also `0x7ffff7039fd8` isn't the ''right'' `environ` according to gdb: there is NULL there. What gdb thinks is `environ` (and my environment does actually appear there) is `0x7ffff7ffe140`... which is also too far away from the relocation site. I wonder how this all worked when you typed `System.Environment.getEnvironment` into GHCi 7.6? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9480#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9480: Segfault in GHC API code using Shelly -------------------------------------+------------------------------------- Reporter: agibiansky | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHC API | Version: 7.8.3 Resolution: | Keywords: Operating System: Linux | Architecture: Unknown/Multiple Type of failure: Runtime | Difficulty: Unknown crash | Blocked By: Test Case: | Related Tickets: #8935 Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by rwbarton): Here is the corresponding `-Dl` output when I build the snippet with 7.6: {{{ Rel entry 101325 is raw(0x323c63 0x113a700000002 0xfffffffffffffffc) lookupSymbol: looking up environ initLinker: start initLinker: idempotent return lookupSymbol: symbol not found `environ' resolves to 0x24af250 Reloc: P = 0x40429ca3 S = 0x24af250 A = 0xfffffffffffffffc }}} This time the linker found `environ` in the executable, which is good (as it's near where we load object files): {{{ rwbarton@morphism:/tmp/shl$ nm /tmp/shl/shl [...] 00000000024af250 V environ@@GLIBC_2.2.5 [...] }}} So, the problem must be that in 7.8 `internal_dlsym` is finding `environ` in one of the `openedSOs` before it gets to looking in the executable. Why does it not look in the executable first? Time to reread #8935 I guess... -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9480#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9480: Segfault in GHC API code using Shelly -------------------------------------+------------------------------------- Reporter: agibiansky | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHC API | Version: 7.8.3 Resolution: | Keywords: Operating System: Linux | Architecture: Unknown/Multiple Type of failure: Runtime | Difficulty: Unknown crash | Blocked By: Test Case: | Related Tickets: #8935 Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by agibiansky): You're right, I've confirmed that {{{ import System.Environment getEnvironment }}} causes the same issue. Thanks for looking into this! Is there any known workaround that can be used in client code? (i.e. can I fix this in any way in my own programs that use GHC API before 7.10 is released) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9480#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9480: Segfault in GHC API code using Shelly -------------------------------------+------------------------------------- Reporter: agibiansky | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHC API | Version: 7.8.3 Resolution: | Keywords: Operating System: Linux | Architecture: Unknown/Multiple Type of failure: Runtime | Difficulty: Unknown crash | Blocked By: Test Case: | Related Tickets: #8935 Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by rwbarton): Yes, build your program with `-dynamic`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9480#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9480: Segfault in GHC API code using Shelly -------------------------------------+------------------------------------- Reporter: agibiansky | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHC API | Version: 7.8.3 Resolution: | Keywords: Operating System: Linux | Architecture: Unknown/Multiple Type of failure: Runtime | Difficulty: Unknown crash | Blocked By: Test Case: | Related Tickets: #8935 Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Changes (by trommler): * cc: trommler (added) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9480#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9480: Segfault in GHC API code using Shelly -------------------------------------+------------------------------------- Reporter: agibiansky | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHC API | Version: 7.8.3 Resolution: | Keywords: Operating System: Linux | Architecture: Unknown/Multiple Type of failure: Runtime | Difficulty: Unknown crash | Blocked By: Test Case: | Related Tickets: #8935 Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by agibiansky): Does anyone know whether this bug has been looked at, or whether it will be fixed for GHC 7.10? I would be very interested in getting it fixed by 7.10, but I do not know how to get started fixing it, or whether it has already been fixed... -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9480#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9480: Segfault in GHC API code using Shelly -------------------------------------+------------------------------------- Reporter: agibiansky | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHC API | Version: 7.8.3 Resolution: | Keywords: Operating System: Linux | Architecture: Unknown/Multiple Type of failure: Runtime | Difficulty: Unknown crash | Blocked By: Test Case: | Related Tickets: #8935 Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by trommler): Could you check if the patch (Phab:D349) for #8935 fixes the issue? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9480#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9480: Segfault in GHC API code using Shelly -------------------------------------+------------------------------------- Reporter: agibiansky | Owner: Type: bug | Status: patch Priority: normal | Milestone: Component: GHC API | Version: 7.8.3 Resolution: | Keywords: Operating System: Linux | Architecture: Unknown/Multiple Type of failure: Runtime | Difficulty: Unknown crash | Blocked By: Test Case: | Related Tickets: #8935 Blocking: | Differential Revisions: Phab:D349 | -------------------------------------+------------------------------------- Changes (by trommler): * status: new => patch * differential: => Phab:D349 Comment: Replying to [comment:7 trommler]:
Could you check if the patch (Phab:D349) for #8935 fixes the issue? I back ported Phab:D349 to ghc 7.8.3 and there is no segfault in the test snippet above anymore.
-- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9480#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9480: Segfault in GHC API code using Shelly -------------------------------------+------------------------------------- Reporter: agibiansky | Owner: Type: bug | Status: patch Priority: normal | Milestone: 7.10.1 Component: GHC API | Version: 7.8.3 Resolution: | Keywords: Operating System: Linux | Architecture: Unknown/Multiple Type of failure: Runtime | Difficulty: Unknown crash | Blocked By: Test Case: | Related Tickets: #8935 Blocking: | Differential Revisions: Phab:D349 | -------------------------------------+------------------------------------- Changes (by trommler): * milestone: => 7.10.1 Comment: Milestone for #8935 is 7.10.1 so setting it here too. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9480#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#9480: Segfault in GHC API code using Shelly
-------------------------------------+-------------------------------------
Reporter: agibiansky | Owner:
Type: bug | Status: patch
Priority: normal | Milestone: 7.10.1
Component: GHC API | Version: 7.8.3
Resolution: | Keywords:
Operating System: Linux | Architecture: Unknown/Multiple
Type of failure: Runtime | Difficulty: Unknown
crash | Blocked By:
Test Case: | Related Tickets: #8935
Blocking: |
Differential Revisions: Phab:D349 |
-------------------------------------+-------------------------------------
Comment (by Austin Seipp
#9480: Segfault in GHC API code using Shelly -------------------------------------+------------------------------------- Reporter: agibiansky | Owner: Type: bug | Status: closed Priority: normal | Milestone: 7.10.1 Component: GHC API | Version: 7.8.3 Resolution: fixed | Keywords: Operating System: Linux | Architecture: Unknown/Multiple Type of failure: Runtime | Difficulty: Unknown crash | Blocked By: Test Case: | Related Tickets: #8935 Blocking: | Differential Revisions: Phab:D349 | -------------------------------------+------------------------------------- Changes (by thoughtpolice): * status: patch => closed * resolution: => fixed Comment: OK, marking as fixed. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9480#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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