Dyplicate symbol definition failure

[TomMD]

When running doctest in the manner described in the readme (a custom setup etc) I get to the point of actually running the test:

cabal test --builddir=build <component>:doctests

This fails on my OS-X machine but works on the Linux based CI systems:

GHC runtime linker: fatal error: I found a duplicate definition for symbol                                    [161/779]
   __ZNK17double_conversion6VectorIcEixEi
whilst processing object file
   /Users/tommd/.cabal/store/ghc-8.10.1/dbl-cnvrsn-2.0.2.0-d1095495/lib/libHSdbl-cnvrsn-2.0.2.0-d1095495.a
The symbol was previously defined in
   /Users/tommd/.cabal/store/ghc-8.10.1/dbl-cnvrsn-2.0.2.0-d1095495/lib/libHSdbl-cnvrsn-2.0.2.0-d1095495.a(hs-double-co
nversion.o)
This could be caused by:
   * Loading two different object files which export the same symbol
   * Specifying the same object file twice on the GHCi command line
   * An incorrect `package.conf' entry, causing some object to be
     loaded twice.
doctests:
lookupSymbol failed in relocateSection (relocate external)
/Users/tommd/.cabal/store/ghc-8.10.1/dbl-cnvrsn-2.0.2.0-d1095495/lib/libHSdbl-cnvrsn-2.0.2.0-d1095495.a: unknown symbol
 `__ZN17double_conversion6StrtofENS_6VectorIKcEEi'
GHC runtime linker: fatal error: I found a duplicate definition for symbol
   __ZN17double_conversion7BitCastIdyEET_RKT0_
whilst processing object file
   /Users/tommd/.cabal/store/ghc-8.10.1/dbl-cnvrsn-2.0.2.0-d1095495/lib/libHSdbl-cnvrsn-2.0.2.0-d1095495.a
The symbol was previously defined in                                                                                      /Users/tommd/.cabal/store/ghc-8.10.1/dbl-cnvrsn-2.0.2.0-d1095495/lib/libHSdbl-cnvrsn-2.0.2.0-d1095495.a(double-conve
rsion.o)
This could be caused by:
   * Loading two different object files which export the same symbol
   * Specifying the same object file twice on the GHCi command line
   * An incorrect `package.conf' entry, causing some object to be
     loaded twice.

Is this a known issue? Should I reroute to GHC's issue tracker?

My last attempt to make a minimal example failed, but I can retry.

[phadej]

The example doctest runner has

traverse_ putStrLn args

Does it print duplicate -package-id=db-cnvrsn-2.0.0.0-d1095495 for you? Or something else suspicious?

[TomMD]

No, it looks good. And just to check I did:

% cat /tmp/doctest-args | sort | uniq | wc -l
      93
% wc -l /tmp/doctest-args
      93 /tmp/doctest-args

And that file has all the args emitted from the output, for example:

% tail /tmp/doctest-args
...
-package-id=dctst-0.17-fe3e7c72
-package-id=template-haskell-2.16.0.0

But it doesn't have even one mention of double conversion:

% grep cnvrsn /tmp/doctest-args
% grep trnsfrmrs /tmp/doctest-args
-package-id=trnsfrmrs-bs-0.4.5.2-0c7e5fc5

[phadej]

Hmm. I think it might be issue in doctest. I see

% doctest src 
Loaded package environment from /code/public-haskell/hkd/.ghc.environment.x86_64-linux-8.6.5
Loaded package environment from /code/public-haskell/hkd/.ghc.environment.x86_64-linux-8.6.5
Examples: 0  Tried: 0  Errors: 0  Failures: 0

when I run doctest, i.e. it loads GHC twice, first to parse modules, and then to actually do testing.

I had no success to reproduce it on linux, having TH using double-conversion and then doctest. In fact, that would be bizarre - as a lot of stuff uses cbits. What particularly happens in your case, no idea.

There are issues close to this in spirit on GHC tracker, e.g. https://gitlab.haskell.org/ghc/ghc/-/issues/8942, but I doubt you would get anywhere without a reproducer. Issue can be anywhere, in GHC itself, Cabal, doctest, or in cabal-doctest.