[GHC] #11748: GHC runtime linker: fatal error: I found a duplicate definition for symbol

[GHC]

#11748: GHC runtime linker: fatal error: I found a duplicate definition for symbol
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        Reporter:  jeiea             |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Template Haskell  |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Windows           |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash                              |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #11223            |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by Phyx-):

 * component:  Compiler (Linking) => Template Haskell
 * architecture:  x86_64 (amd64) => Unknown/Multiple


Comment:

 The linker didn't change between `8.0.1` and `8.0.2`. I think this is a
 general limitation of TH. At least the current implementation.

 The linker is correct in saying you have a duplicate symbol. One is coming
 from the code that `inline-c` generates, which ends up producing a symbol
 called `rgb` (probably from the macro `RGB` in `windows.h`).

 The second comes from the `Win32` package. The `8.0.2` linker should have
 explicitly pointed these out. The issue is that TH uses a version of
 `Win32` that has all the symbols in the same object file. So the link has
 no choice but to load it all, even if you don't use `rgb` because it's in
 the same object file. If instead TH would use the archive instead of the
 `whole-package-as-object-file` variant then it should work.

 I'll leave this open so someone who knows more about TH can comment on the
 issue.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11748#comment:12>
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