Ticket #187 (new defect)

Opened 6 years ago

Last modified 4 years ago

With TH, when doing "cabal haddock", GHCi "couldn't find symbol"

Reported by: MikolajKonarski Owned by:
Priority: major Milestone:
Version: 2.9.2 Keywords:


This is a copy of the ticket http://hackage.haskell.org/trac/hackage/ticket/898, I've filed for Cabal. I include the whole ticket text below.

GHC 7.2.1, Cabal HEAD, Haddock 2.9.2. The message

During interactive linking, GHCi couldn't find the following symbol:

How to reproduce: get package http://hackage.haskell.org/package/Allure-0.4.2, cabal install, cabal haddock --executables and you should get the following:

Running Haddock for Allure-0.4.2...
Warning: The documentation for the following packages are not installed. No
links will be generated to these packages: ConfigFile-1.1.1, HUnit-,
MissingH-, ffi-1.0, rts-1.0, cairo-0.12.1, deepseq-, gio-0.12.1,
glib-0.12.1, gtk-0.12.1, hslogger-1.1.5, mtl-, network-,
pango-0.12.1, parsec-3.1.2, random-, regex-base-0.93.2,
regex-compat-0.95.1, regex-posix-0.95.1, text-, transformers-,
Preprocessing executable 'BotAllure' for Allure-0.4.2...
haddock coverage for dist/build/tmp-28531/src/Bot.hs:     0/3   0%
Warning: Main: could not find link destinations for:
Documentation created: dist/doc/html/Allure/BotAllure/index.html
Preprocessing executable 'Allure' for Allure-0.4.2...
haddock coverage for dist/build/autogen/Paths_Allure.hs:     0/4   0%
haddock coverage for dist/build/tmp-28531/src/Utils/File.hs:     0/3   0%
haddock coverage for dist/build/tmp-28531/src/Frequency.hs:     0/6   0%
haddock coverage for dist/build/tmp-28531/src/Strategy.hs:     1/7  14%
haddock coverage for dist/build/tmp-28531/src/Content/Content.hs:     0/2   0%
haddock coverage for dist/build/tmp-28531/src/Utils/Multiline.hs:     1/2  50%

During interactive linking, GHCi couldn't find the following symbol:
This may be due to you not asking GHCi to load extra object files,
archives or DLLs needed by your current session.  Restart GHCi, specifying
the missing library using the -L/path/to/object/dir and -lmissinglibname
flags, or simply by naming the relevant files on the GHCi command line.
Alternatively, this link failure might indicate a bug in GHCi.
If you suspect the latter, please send a bug report to:

The same problem for a library, with or without executables, with the same code. Hiding, in the library, the offending module Multiline does not help. The only thing that helps is eta-expanding the Multiline code as follows:

-multiline  = TQ.QuasiQuoter (TH.litE . TH.stringL) undefined undefined undefined
+multiline  = TQ.QuasiQuoter (\x -> (TH.litE . TH.stringL) x) undefined undefined undefined

and _not_ using the function in the only place where it's used.

Change History

Changed 5 years ago by anonymous

  • milestone 2.10.0 deleted

Milestone 2.10.0 deleted

Changed 4 years ago by duplode

The same problem was met in this module of threepenny-gui, also triggered by a quasiquoter definition:

include = QuasiQuoter
        { quoteExp = f -- only used as an expression,
        , quotePat = undefined -- hence all other use cases undefined
        , quoteType = undefined
        , quoteDec = undefined
    f s = TH.LitE . TH.StringL <$> TH.runIO (readFile $ root ++ s)

As a workaround, adding an otherwise unnecessary TemplateHaskell pragma averted the issue. (Tested with GHC 7.6.3, Cabal and Haddock 2.13.2.)

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