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[20 of 20] Compiling Main             ( ./Main.hs, dist/build/cabal/cabal-tmp/Main.o )
The interface for `main:Hackage.Config'
Declaration for savedConfigToConfigFlags
Unfolding of Hackage.Config.savedConfigToConfigFlags:
  Can't find interface-file declaration for variable Distribution.Simple.Setup.a401
    Probable cause: bug in .hi-boot file, or inconsistent .hi file
    Use -ddump-if-trace to get an idea of which file caused the error
Linking dist/build/cabal/cabal ...
dist/build/cabal/cabal-tmp/Hackage/Config.o: In function `sfsu_info':
(.text+0x70cc): undefined reference to `Cabalzm1zi3zi3_DistributionziSimpleziSetup_a401_closure'
dist/build/cabal/cabal-tmp/Hackage/Config.o: In function `rf7U_closure':
(.data+0xf28): undefined reference to `Cabalzm1zi3zi3_DistributionziSimpleziSetup_a401_closure'
collect2: ld returned 1 exit status

Now, the inconsistent .hi file was entirely my fault. However note that ghc --make did not stop at the error! It continued and tried to link.

This is bad because sometimes linker errors are very long and a user might loose the real source of the error.

The error gets raised in iface/TcIface.lhs by importDecl. The uses of that function look like they are translating the error into failure in other monads ok. It's not immediately obvious at what point in the propagation of this error it gets ignored and linking continues irrespective.

It should not be too hard to reproduce I hope. Generating inconsistent .hi files is fairly easy to do. In this case I just built cabal-install against an existing Cabal. Then rebuilt and re-registered a slightly changed Cabal lib. Then did another build of cabal-install without cleaning first.

Trac metadata

Trac field	Value
Version	6.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Unknown
Architecture	Unknown