libraries/base/System/Posix/Types.hs: tries to define Floating instance for opaque type

I've noticed it as a build failure on openbsd-6 but on linux behaviour is strange as well.

Build failure:

libraries/base/System/Posix/Types.hs:217:100: error:
    * No instance for (Fractional Int32)
        arising from the 'deriving' clause of a data type declaration
      Possible fix:
        use a standalone 'deriving instance' declaration,
          so you can specify the instance context yourself
    * When deriving the instance for (Fractional CTimer)

On openbsd-6.0 timer_t is an int32:

# gcc -E /usr/include/time.h | grep timer_t                                                                                                                                                   
typedef __int32_t __timer_t;
typedef __timer_t timer_t;

On amd64-linux-glibc it's void*:

$ gcc -E /usr/include/time.h | grep timer_t
typedef void * __timer_t;
typedef __timer_t timer_t;

But base's configure detects it as Double (by chance) on amd64-linux-glibc.

System.Posix.Types> :t CTimer 
CTimer :: Double -> CTimer

Trac metadata

Trac field	Value
Version	8.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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