#1452: "undefined reference" while linking executable (for cyclic import
project)
in ghc-6.6.1
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Reporter: guest | Owner: guest
Type: bug | Status: assigned
Priority: normal | Milestone:
Component: Compiler | Version: 6.6.1
Severity: normal | Resolution:
Keywords: cyclic import | Difficulty: Moderate (1 day)
Os: Linux | Testcase:
Architecture: x86 |
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Comment (by simonpj):
Just to make this 100% explicit:
* Cabal uses ghc --make to build a bunch of .o files (including Match.o)
* Cabal then links the .o files that are listed in dm.cabal (as exposed
or other) to make a .a file. This list accidentally excludes Match.o
* Cabal copies the .a file and the .hi files listed in dm.cabal (as
exposed or other) to the install place, and registers them. Again, this
list excludes Match.o
As a result, a client of the package compiles all right (so long as it
does not import Match) but fails at the link stage, lacking symbols in
Match.
This seems like a bug in Cabal, because it allows you to build and install
an unusable package. Possible solutions I can think of:
* Cabal does its own dependency analysis and calls GHC one module at a
time
* GHC gets a flag which prevents it finding any module other than those
listed on the command line (although it may still do dependency analysis
to figure out which order to compile them in)
* The .cabal file is no longer reqd to list non-exposed modules. Instead
Cabal works out what the non-exposed modules are (perhaps by calling GHC
-M or something similar).
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1452>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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