Dear all, Giving a try to GHC 6.8.1 under Windows, I stumble upon the following issue (yes, I'm struggling with HDirect), which did not occur with the 6.6 version : the linking phase of my project fails with $ C:/ghc/ghc-6.8.1/bin/ghc -o ihc.exe -fglasgow-exts -static -fvia-C -Rghc-timing -Wall -recomp AbsHUtils.o AbstractH.o Attribute.o Bag.o [... lots of files, among which we have CoreUtils.o ...] CoreUtils.o(.text+0x15066):ghc2436_0.hc: undefined reference to `containerszm0zi1zi0zi0_DataziGraph_stronglyConnComp_closure' CoreUtils.o(.text+0x150b0):ghc2436_0.hc: undefined reference to `containerszm0zi1zi0zi0_DataziGraph_stronglyConnComp_closure' CoreUtils.o(.text+0x1ac23):ghc2436_0.hc: undefined reference to `__stginit_containerszm0zi1zi0zi0_DataziGraph_' IDLUtils.o(.text+0x6026):ghc768_0.hc: undefined reference to `containerszm0zi1zi0zi0_DataziGraph_stronglyConnComp_closure' IDLUtils.o(.text+0x6070):ghc768_0.hc: undefined reference to `containerszm0zi1zi0zi0_DataziGraph_stronglyConnComp_closure' IDLUtils.o(.text+0xc607):ghc768_0.hc: undefined reference to `__stginit_containerszm0zi1zi0zi0_DataziGraph_' collect2: ld returned 1 exit status Indeed, that symbol is undefined in the CoreUtils file : $ nm CoreUtils.o | grep strongl U _containerszm0zi1zi0zi0_DataziGraph_stronglyConnComp_closure As far as I understand, this is a reference to the Data.Graph function stronglyConnComp (which can be seen in the « containers-0.1.0.0/Data/Graph.hi » interface file ; according to the haddock documentation of GHC, that function is indeed in the Data.Graph module, which is imported by the CoreUtils.lhs file). What is strange to me is that $ nm libHSghc.a | grep strongl gives : 00000598 D _ghczm6zi8zi1_Digraph_stronglyConnComp_closure which could explain why that function is not found. May be I'm looking at the wrong file, I don't know much of the linking and name-mangling process at hand here (Digraph vs. DataziGraph ?). What I do not understand is what causes that issue, which seems to only concern the Data.Graph module so far. Hopes this makes sense to you, Sincerely yours, Samuel