#2190: unionBuildInfo should not always use nub
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Reporter: prj | Owner:
Type: bug | Status: new
Priority: normal | Component: libraries (other)
Version: 6.8.2 | Severity: normal
Keywords: unionBuildInfo nub | Testcase:
Architecture: Multiple | Os: Multiple
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In libraries/Cabal/Distribution/PackageDescription.hs, the unionBuildInfo
function combines, for example, ldOptions from two BuildInfos, using nub
to eliminate duplicate arguments. This is wrong for ldOptions and some
other elements. For example, if ldOptions contains:
{{{-Xlinker -R -Xlinker /dir1 -Xlinker -R -Xlinker /dir2}}}
Then the nubbed result is:
{{{-Xlinker -R /dir1 /dir2}}}
which doesn't work at all. There may be some redundancy that could be
eliminated, but for arguments passed to external programs, it can only be
done safely by understanding the semantics of the arguments. Similarly
for extraLibs, {{{-lfoo -lbar -lfoo}}} may be necessary if {{{libfoo}}}
and {{{libbar}}} reference each other's symbols.
Using nub is wrong for at least cppOptions, ccOptions, ldOptions, and
extraLibs. But I think it is necessary for some other BuildInfo
components, like hsSourceDirs, so it can't be removed completely; that
results in an error while building GHC:
{{{
Preprocessing library unix-2.3.0.0...
Generating Makefile unix-2.3.0.0...
Setup: makefile: can't cope with multiple hs-source-dirs yet, sorry
}}}
So {{{combine}}} could take an extra arguments, which would be nub in some
cases or id in others.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2190>
GHC <http://www.haskell.org/ghc/>
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