[GHC] #7568: Can't dynamically load DLL-using libraries on Windows x86_64

[GHC]

#7568: Can't dynamically load DLL-using libraries on Windows x86_64
-----------------------+----------------------------------------------------
Reporter:  bos         |          Owner:                
    Type:  bug         |         Status:  new           
Priority:  normal      |      Component:  Compiler      
 Version:  7.6.1       |       Keywords:                
      Os:  Windows     |   Architecture:  x86_64 (amd64)
 Failure:  GHCi crash  |      Blockedby:                
Blocking:              |        Related:                
-----------------------+----------------------------------------------------
 I've spent the past day trying to understand and fix this downstream bug:

 https://github.com/tibbe/hashable/issues/46

 There are two unrelated bugs at play. Please let me know if you'd like me
 to file them separately.

 == Test case

 Both bugs have a very simple reproduction script.

 {{{
 import Data.Hashable
 import Data.Text

 main = print . hash . pack $ "/"
 }}}

 == First bug

 The first problem arises when we compile some C code for inclusion into a
 Haskell library, and that C code includes references to functions in a
 standard Windows DLL.

 In this case, names from the DLL are prefixed with __imp_, in the
 expectation that the mingw "import library" will be linked against.
 However, the ghc runtime linker knows nothing about these import libraries
 (they're .a files buried in the mingw tree) and just tries to load the
 DLL, whereupon symbol resolution fails.

 To reproduce:

 {{{
 git clone git://github.com/tibbe/hashable.git
 git checkout master
 cabal install
 runghc ....../Crash.hs
 }}}

 == Second bug

 I came upon the second problem while trying to work around the first.

 {{{
 cd hashable
 git checkout origin/win64
 cabal install
 runghc ...../Crash.hs
 }}}

 In this case, I get a crash due to the wrong relocation size being used:

 {{{
 Crash.hs: internal error: R_X86_64_PC32: High bits are set in 7fefc4ece1d
 for CryptReleaseContext
     (GHC version 7.6.1 for x86_64_unknown_mingw32)
 }}}

 This latter case looks similar to #7134.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7568>
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