[Haskell-cafe] Windows, doctest and auxiliary FFI wrappers?

[Viktor Dukhovni]

On Tue, Oct 15, 2019 at 03:47:46AM -0400, Viktor Dukhovni wrote:

> What I've tried:
> 
>     2.  Build a separate internal library (supported in Cabal
> 	2.0 and later), which is a dependency of the main library
> 	and links in the C glue code, but this proved to be a
> 	significant rabbit hole...

Following up on my own post, for the record I should note that in
fact the second approach work out with GHC 8.[468].x and Cabal 2.x
through the magic of .ghc.environment.* files.  With Cabal 3.0,
these are no longer written by default, but it suffices to create
a cabal.project file containing just:

	packages: .
	write-ghc-environment-files: always

The crux of my issue seems to be that this does not work with older
GHC releases (e.g. 8.0.2 and 8.2.2) and perhaps the flag was not
set by the Cabal used in AppVeyor on Windows or some other nit got
in the way.

I now have doctests compiling and running with GHC 8.[468] on Linux
and so far just 8.6.5 on Windows.  The custom C-code dependency
was, as hoped for, satisfied by the addition of the internal library
package to the doctest command arguments, I only had to hardcode
the format of the "inplace" package-id.

    https://github.com/kazu-yamamoto/dns/blob/master/test2/doctests.hs

Sadly, on Windows the doctests mostly end up hanging and timing out
after an hour, but that's a separate issue, perhaps

    <https://gitlab.haskell.org/ghc/ghc/issues/16917>

-- 
	Viktor.